Patent Publication Number: US-2012041410-A1

Title: Disposable Absorbent Article Having Soft-Clothlike Backsheet

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This applications is a continuation of application Ser. No. 09/297,774, filed May 7, 1999, which is a National Phase entry and claims priority to PCT/US96/18339, filed Nov. 8, 1996, the substance of which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to disposable absorbent articles such as disposable diapers and, more particularly, to disposable absorbent articles having soft-clothlike backsheets. 
     BACKGROUND OF THE INVENTION 
     Infants and other incontinent individuals wear disposable absorbent articles such as diapers to receive and contain urine and other body exudates. Absorbent articles function both to contain the discharged materials and to isolate these materials from the body of the wearer and from the wearer&#39;s garments and bed clothing. Disposable absorbent articles having many different basic designs are known to the art. It is also known that the exterior of disposable diapers can be covered with a flexible, liquid and vapor impervious sheet, which prevents any absorbed liquid from passing through the diaper and soiling adjacent articles such as clothing, bedding and the like. These outer covers, generally referred to as backsheets, are often constructed from fluid impervious films such as polyethylene. Although such backsheets do prevent liquid from passing through the diaper, they also can make the diaper feel hot and uncomfortable to wear because of their impermeability to air and/or moisture. 
     Backsheets which are pervious to vapor are generally known as breathable backsheets and have been described in the art. In general, these backsheets are intended to allow the passage of vapor through them while retarding the passage of liquid. The conventional breathable backsheets are usually made of microporous thin plastic films. For example, U.S. Pat. No. 3,156,242 issued to Crowe, Jr. on Nov. 10, 1964 teaches the use of a microporous film as a breathable backsheet. U.S. Pat. No. 3,881,489, issued to Hartwell on May 6, 1975, teaches a breathable backsheet comprising in combination two layers. The first layer is a low void volume perforated thermoplastic film and the second layer is a porous high void volume hydrophobic tissue. 
     Some recent disposable diapers use cloth-like backsheets to provide a visual breathability and an improved natural appearance and/or impression. A typical structure of such cloth-like backsheets comprises a nonwoven web joined to the outer-facing surface of a microporous thin plastic in order to form a laminate. 
     However, such cloth-like backsheets are not completely satisfactory to consumers because they are either stiff, bulky or have a rough surface. For example, the friction between the backsheet and the wearer&#39;s skin often causes skin rash on the wearer&#39;s legs. Further, the friction between the backsheet and the wearer&#39;s clothes generates a noise and is also uncomfortable to the wearer. It is believed that such frictions are caused by excessive crispness and roughness at the surface of backsheets. 
     SUMMARY OF THE INVENTION 
     Briefly stated, the present invention relates to a disposable absorbent article. In one aspect of the invention, the disposable absorbent article comprises a containment assembly comprising a topsheet, a backsheet and an absorbent core disposed between the topsheet and the backsheet. The backsheet comprises a nonwoven web positioned at the outermost portion of the absorbent article, for covering at least a portion of the outermost portion of the absorbent core of the article. The backsheet has a hand value of Koshi of less than about 11.0, a hand value of Shari of from about 5.0 to about 7.0, and a hand value of Fukurami of less than about 0.5. Preferably, the backsheet has a fuzz level of less than about 0.24 mg/cm 2 . More preferably, the nonwoven web is a spunbonded nonwoven web. In a preferred embodiment, the spunbonded nonwoven web has a tensile strength of at least 180 gf/cm in the traverse direction of the disposable absorbent article. 
     In another aspect of the invention, the disposable absorbent article comprises a containment assembly comprising a topsheet, a backsheet and an absorbent core disposed between the topsheet and the backsheet. The backsheet comprises a nonwoven web positioned at the outermost portion of the absorbent article, for covering at least a portion of the outermost portion of the absorbent core of the article. The nonwoven web is a spunbonded nonwoven web comprising spunbonded bi-component plastic fibers. Preferably, the spunbonded nonwoven web is placed in the disposable absorbent article so that the fiber direction of the spunbonded bi-component plastic fibers is aligned with the longitudinal direction of the disposable absorbent article. More preferably, the spunbonded nonwoven web has a tensile strength of at least 80 gf/cm in the traverse direction of the disposable absorbent article. In a preferred embodiment, the nonwoven web has a hand value of Koshi of less than about 16.0, a hand value of Shari of from about 0.5 to about 9.5, and a hand value of Fukurami of less than about 5.0. In a further preferred embodiment, the nonwoven web has a fuzz level of less than about 1.0 mg/cm 2 . 
     Preferably, the backsheet further comprises a plastic film having an outer-facing surface and a body-facing surface, and the nonwoven web is joined with the outer-facing surface of the plastic film to form a laminate. 
    
    
     
       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 like designations are used to designate substantially identical elements, and in which: 
         FIG. 1  is a plane view of a disposable diaper embodiment according to the present invention having portions cut away to reveal underlying structure, the inner surface of the diaper is facing the viewer; 
         FIG. 2  is an enlarged, cross-sectional view of one embodiment of a disposable absorbent article comprising a backsheet; 
         FIG. 3  is a plane view of the sample used for the tensile property measurement; 
         FIG. 4  is a graph showing the tensile property of the sample; 
         FIGS. 5A and 5B  are schematic diagrams explaining the measurement for the bending property; 
         FIG. 6  is a graph showing the bending property of the sample; 
         FIGS. 7A and 7B  are schematic diagrams explaining the measurement for the surface roughness; 
         FIGS. 8A and 8B  are schematic diagrams explaining the measurement for the surface friction; 
         FIG. 9  shows the conditions of the steel plate used for the surface roughness and friction measurements; 
         FIG. 10  shows the changes of the friction coefficient along the surface of the sample; 
         FIG. 11  shows the changes of the thickness along the surface of the sample; 
         FIG. 12  is a plane view of the sample used for the shearing property measurement; 
         FIG. 13  is a graph showing the shearing property of the sample; 
         FIG. 14  is a plane view of the sample used for the compression property measurement; 
         FIG. 15  is a graph showing the compression property of the sample; 
         FIG. 16  is a schematic diagram explaining the fuzz level measurement. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     1. Absorbent Article 
     As used herein, the term “absorbent article” refers to devices which absorb and contain body exudates, and, more specifically, refers to devices which are placed against or in proximity to the body of the wearer to absorb and contain the various exudates discharged from the body. The term “disposable” is used herein to describe absorbent articles which are not intended to be laundered or otherwise restored or reused as an absorbent article (i.e., they are intended to be discarded after a single use and, preferably, to be recycled, composted or otherwise disposed of in an environmentally compatible manner). A “unitary” absorbent article refers to absorbent articles which are formed of separate parts united together to form a coordinated entity so that they do not require separate manipulative parts like a separate holder and liner. A preferred embodiment of an absorbent article of the present invention is the unitary disposable absorbent article, diaper  20 , shown in  FIG. 1 . As used herein, the term “diaper” refers to an absorbent article generally worn by infants and incontinent persons that is worn about the lower torso of the wearer. It should be understood, however, that the present invention is also applicable to other absorbent articles such as incontinence briefs, incontinence undergarments, diaper holders and liners, feminine hygiene garments, training pants, and the like. 
       FIG. 1  is a plane view of the diaper  20  in its flat-out, uncontracted state (i.e., with elastic induced contraction pulled out) with portions of the structure being cut-away to more clearly show the construction of the diaper  20  and with the portion of the diaper  20  which faces the wearer, the inner surface  40 , facing the viewer. As shown in  FIG. 1 , the diaper  20  preferably comprises a containment assembly  22  comprising a liquid pervious topsheet  24 ; a liquid impervious backsheet  26  joined to the topsheet; and an absorbent core  28  positioned between the topsheet  24  and the backsheet  26 . The absorbent core  28  has a pair of opposing longitudinal edges  60 , an inner surface and an outer surface. The diaper preferably further comprises side panels  30 ; elasticized leg cuffs  32  (each having an inboard edge  35  and an outboard edge  32 ); elasticized waistbands  34 ; and a fastening system  36  preferably comprising a pair of securement members  37  and a landing member  38 . The backsheet  26  prevents the exudates absorbed and contained in the absorbent core  28  from wetting articles which contact the diaper  20  such as bed sheets and undergarments. 
     The diaper  20  has an inner surface  40  (facing the viewer in  FIG. 1 ), an outer surface  42  opposed to the inner surface  40 , a rear waist region  44 , a front waist region  46  opposed to the rear waist region  44 , a crotch region  48  positioned between the rear waist region  44  and the front waist region  46 , and a periphery which is defined by the outer perimeter or edges of the diaper  20  in which the side edges are designated  50  and the end edges are designated  52 . The inner surface  40  of the diaper  20  comprises that portion of the diaper  20  which is positioned adjacent to the wearer&#39;s body during use (i.e., the inner surface  40  generally is formed by at least a portion of the topsheet  24  and other components joined to the topsheet  24 ). The outer surface  42  comprises that portion of the diaper  20  which is positioned away from the wearer&#39;s body (i.e., the outer surface  42  is generally formed by at least a portion of the backsheet  26  and other components joined to the backsheet  26 ). As used herein, the term “joined” encompasses configurations whereby an element is directly secured to the other element by affixing the element directly to the other element, and configurations whereby 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. The rear waist region  44  and the front waist region  46  extend from the end edges  52  of the periphery to the crotch region  48 . 
     The diaper  20  also has two centerlines, a longitudinal centerline  100  and a transverse centerline  110 . The term “longitudinal”, as used herein, refers to a line, axis, or direction in the plane of the diaper  20  that is generally aligned with (e.g. approximately parallel with) a vertical plane which bisects a standing wearer into left and right halves when the diaper  20  is worn. The term “transverse”, as used herein, are interchangeable and refer to a line, axis or direction which lies within the plane of the diaper that is generally perpendicular to the longitudinal direction (which divides the wearer into front and back body halves). 
     The topsheet  24  and the backsheet  26  have length and width dimensions generally larger than those of the absorbent core  28 . The topsheet  24  and the backsheet  26  extend beyond the edges of the absorbent core  28  to thereby form the periphery of the diaper  20 . While the topsheet  24 , the backsheet  26 , and the absorbent core  28  may be assembled in a variety of well known configurations, exemplary containment assembly configurations are described generally in U.S. Pat. No. 3,860,003 entitled “Contractible Side Portions for Disposable Diaper” which issued to Kenneth B. Buell on Jan. 14, 1975; and U.S. Pat. No. 5,151,092 entitled “Absorbent Article With Dynamic Elastic Waist Feature Having A Predisposed Resilient Flexural Hinge” which issued to Kenneth B. Buell et al., on Sep. 29, 1992; each of which is incorporated herein by reference. 
     The absorbent core  28  may be any absorbent member which is generally compressible, conformable, non-irritating to the wearer&#39;s skin, and capable of absorbing and retaining liquids such as urine and other certain body exudates. As shown in  FIG. 1 , the absorbent core  28  has an outer-facing (or garment-facing) side, a body-facing side, a pair of side edges, and a pair of waist edges. The absorbent core  28  may be manufactured in a wide variety of sizes and shapes (e.g., rectangular, hourglass, “T”-shaped, asymmetric, etc.) and from a wide variety of liquid-absorbent materials commonly used in disposable diapers and other absorbent articles such as comminuted wood pulp which is generally referred to as airfelt. Examples of other suitable absorbent materials include creped cellulose wadding; meltblown polymers including coform; chemically stiffened, modified or cross-linked cellulosic fibers; tissue including tissue wraps and tissue laminates; absorbent foams; absorbent sponges; superabsorbent polymers; absorbent gelling materials; or any equivalent material or combinations of materials. 
     The configuration and construction of the absorbent core  28  may vary (e.g., the absorbent core may have varying caliper zones, a hydrophilic gradient, a superabsorbent gradient, or lower average density and lower average basis weight acquisition zones; or may comprise one or more layers or structures). Further, the size and absorbent capacity of the absorbent core  28  may also be varied to accommodate wearers ranging from infants through adults. However, the total absorbent capacity of the absorbent core  28  should be compatible with the design loading and the intended use of the diaper  20 . 
     One embodiment of the diaper  20  has an asymmetric, modified T-shaped absorbent core  28  having ears in the front waist region but a generally rectangular shape in the rear waist region. Exemplary absorbent structures for use as the absorbent core  28  of the present invention that have achieved wide acceptance and commercial success are described in U.S. Pat. No. 4,610,678 entitled “High-Density Absorbent Structures” issued to Weisman et al. on Sep. 9, 1986; U.S. Pat. No. 4,673,402 entitled “Absorbent Articles With Dual-Layered Cores” issued to Weisman et al. on Jun. 16, 1987; U.S. Pat. No. 4,888,231 entitled “Absorbent Core Having A Dusting Layer” issued to Angstadt on Dec. 19, 1989; and U.S. Pat. No. 4,834,735, entitled “High Density Absorbent Members Having Lower Density and Lower Basis Weight Acquisition Zones”, issued to Alemany et al. on May 30, 1989. The absorbent core may further comprise the dual core system containing an acquisition/distribution core of chemically stiffened fibers positioned over an absorbent storage core as detailed in U.S. Pat. No. 5,234,423, entitled “Absorbent Article With Elastic Waist Feature and Enhanced Absorbency” issued to Alemany et al., on Aug. 10, 1993; and in U.S. Pat. No. 5,147,345, entitled “High Efficiency Absorbent Articles For Incontinence Management” issued to Young, LaVon and Taylor on Sep. 15, 1992. All of these patents are incorporated herein by reference. 
     The topsheet  24  is preferably positioned adjacent the inner surface  62  of the absorbent core  28  and is preferably joined thereto and to the backsheet  26  by attachment means (not shown) such as those well known in the art. Suitable attachment means are described with respect to joining the backsheet  26  to the absorbent core  28 . In a preferred embodiment of the present invention, the topsheet  24  and the backsheet  26  are joined directly to each other in the diaper periphery and are indirectly joined together by directly joining them to the absorbent core  28  by any suitable attachment means. 
     The topsheet  24  is preferably compliant, soft feeling, and non-irritating to the wearer&#39;s skin. Further, the topsheet  24  is preferably liquid pervious permitting liquids (e.g., urine) to readily penetrate through its thickness. A suitable topsheet  24  may be manufactured from a wide range of materials such as woven and nonwoven materials; 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. The topsheet  24  is preferably made of a hydrophobic material to isolate the wearer&#39;s skin from liquids which have passed through the topsheet  24  and are contained in the absorbent core  28  (i.e. to prevent rewet). If the topsheet  24  is made of a hydrophobic material, at least the upper surface of the topsheet  24  is treated to be hydrophilic so that liquids will transfer through the topsheet more rapidly. This diminishes the likelihood that body exudates will flow off the topsheet  24  rather than being drawn through the topsheet  24  and being absorbed by the absorbent core  28 . The topsheet  24  can be rendered hydrophilic by treating it with a surfactant. Suitable methods for treating the topsheet  24  with a surfactant include spraying the topsheet  24  material with the surfactant and immersing the material into the surfactant. A more detailed discussion of such a treatment and hydrophilicity is contained in U.S. Pat. No. 4,988,344 entitled “Absorbent Articles with Multiple Layer Absorbent Layers” issued to Reising, et al on Jan. 29, 1991 and U.S. Pat. No. 4,988,345 entitled “Absorbent Articles with Rapid Acquiring Absorbent Cores” issued to Reising on Jan. 29, 1991, each of which is incorporated by reference herein. 
     An alternative preferred topsheet comprises an apertured formed film. Apertured formed films are preferred for the topsheet because they are pervious to body exudates and yet non-absorbent and have a reduced tendency to allow liquids to pass back through and rewet the wearer&#39;s skin. Thus, the surface of the formed film which is in contact with the body remains dry, thereby reducing body soiling and creating a more comfortable feel for the wearer. Suitable formed films are described in U.S. Pat. No. 3,929,135, entitled “Absorptive Structures Having Tapered Capillaries”, which issued to Thompson on Dec. 30, 1975; U.S. Pat. No. 4,324,246 entitled “Disposable Absorbent Article Having A Stain Resistant Topsheet”, which issued to Mullane, et al. on Apr. 13, 1982; U.S. Pat. No. 4,342,314 entitled “Resilient Plastic Web Exhibiting Fiber-Like Properties”, which issued to Radel. et al. on Aug. 3, 1982; U.S. Pat. No. 4,463,045 entitled “Macroscopically Expanded Three-Dimensional Plastic Web Exhibiting Non-Glossy Visible Surface and Cloth-Like Tactile Impression”, which issued to Ahr et al. on Jul. 31, 1984; and U.S. Pat. No. 5,006,394 “Multilayer Polymeric Film” issued to Baird on Apr. 9, 1991. Each of these patents are incorporated herein by reference. 
     The backsheet  26  of the present invention comprises a nonwoven web  90  positioned at the outermost portion of the absorbent article, which covers at least a portion of the outermost portion of the absorbent core of the article. In preferred embodiments, the nonwoven web  90  is present on at least 30%, more preferably at least 70%, most preferably at least 90% of the area of the outer-facing surface of the absorbent article. In preferred embodiments, the backsheet  26  further comprises a plastic film  27  having an outer-facing surface and a body-facing surface, and the nonwoven web  90  is joined with the outer-facing surface of the plastic film to form a laminate. The nonwoven web may be joined to the plastic film by any suitable attachment means known in the art. For example, the nonwoven web may be secured to the plastic film by a uniform continuous layer of adhesive, a patterned layer of adhesive, or an array of separate lines, spirals, or spots of adhesive. Suitable adhesives include a hotmelt adhesive obtainable from Nitta Findley Co., Ltd., Osaka, Japan as H-2476-01, and a hotmelt adhesive obtainable from H.B. Fuller Japan Co., Ltd., Osaka, Japan as JM-6064. Preferably, the density of the adhesive applied between the nonwoven web and the plastic film is from about 0.05 g/m 2  to about 7.0 g/m 2 , more preferably from about 0.1 g/m 2  to about 5.0 g/m 2 , most preferably from about 0.2 g/m 2  to about 1.5 g/m 2 . 
     The plastic film is preferably impervious to liquids (e.g., urine) and is preferably manufactured from a thin plastic film. However, the plastic film permits vapors to escape from the diaper  20 . In a preferred embodiment, a microporous polyethylene film is used for the plastic film. A suitable microporous polyethylene film is manufactured by Mitsui Toatsu Chemicals, Inc., Nagoya, Japan and marketed in the trade as Espoir No. 
     A suitable material for the plastic film is a thermoplastic film having a thickness of from about 0.012 mm (0.5 mil) to about 0.051 mm (2.0 mils), preferably comprising polyethylene or polypropylene. Preferably, the plastic film has a basis weight of from about 5 g/m 2  to about 35 g/m 2 . However, it should be noted that other flexible liquid impervious materials may be used. As used herein, the term “flexible” refers to materials which are compliant and which will readily conform to the general shape and contours of the wearer&#39;s body. In preferred embodiments, the backsheet  26  of the present invention may comprise a single member such as the film described above, or may comprise a number of materials joined together to form the plastic film  27 . 
     Preferably, the nonwoven web  90  may cover all or substantially all of the outer-facing surface  70  of the plastic film  27 , or may cover only discrete predetermined portions. In a preferred embodiment, the nonwoven web  90  covers all or substantially all of the plastic film  27  in order to provide the diaper with a cloth-like appearance and feel. Further, the nonwoven web  90  may provide the diaper with a low cost landing zone capable of engaging the hooks of a hook and loop type fastener. (Such a landing zone could be utilized as a portion of a primary fastening system or as a means for disposing of a soiled diaper.) 
     In a preferred embodiment, the plastic film  27  exists only in the containment assembly area  22  (and does not exist the side panel areas  30 ), while the nonwoven web  90  exists the both of the containment assembly area  22  and the side panel areas  30 . The nonwoven web  90  covers all of the outer-facing surface  70  of the plastic film  27 . 
     The nonwoven web  90  is preferably air pervious. The nonwoven web may comprise natural fibers (e.g. cotton or wood fibers), or may comprise fibers of polyethylene, polypropylene, polyester, polyethylene terephthalate, or any combination of such fibers. Further, the nonwoven web may be carded, spunmelt, meltblown or air-through bonded or have any other characteristic or be manufactured in any manner known in the art. Preferably, the nonwoven web is comprised of sufficient thermoplastic material to allow for thermal bonding of the material to other components of the diaper. 
     An especially preferred nonwoven web is a spunbonded nonwoven web, preferably made of bi-component fibers. Preferably, the bi-component fiber contains a polyethylene and a polypropylene. More preferably, the bi-component fiber has a core of the polypropylene and a sheath of the polyethylene. In preferred embodiments, the bi-component fiber has from about 55% to about 95% by weight of the polyethylene. Most preferably, the bi-component fiber has from about 70% to about 90% by weight of the polyethylene. 
     In preferred embodiments, the spunbonded nonwoven web is placed in the disposable absorbent article so that the fiber direction of the spunbonded bi-component plastic fibers is aligned with the longitudinal direction of the disposable absorbent article. Preferably, the spunbonded nonwoven web has a tensile strength of at least 80 gf/cm, more preferably of at least 180 gf/cm in the traverse direction of the disposable absorbent article. 
     An alternative preferred nonwoven web is a carded nonwoven web, preferably made of bi-component fibers. Preferably, the bi-component fiber contains a polyethylene and a polyethylene terephthalate. Preferably, the bi-component fiber has a core of the polyethylene terephthalate and a sheath of the polyethylene. In preferred embodiments, the bi-component fiber has from about 50% to about 95% by weight of the polyethylene. Most preferably, the bi-component fiber has from about 55% to about 95% by weight of the polyethylene. 
     In a further alternative embodiment, the bi-component fiber may contain different types of polypropylene. More preferably, the bi-component fiber has a core of the polypropylene which has a higher melting point and a sheath of the polyethylene which has a lower melting point. 
     In a preferred embodiment, the nonwoven web is a carded nonwoven web obtainable from Havix Co., LTD., Gifu, Japan as E-2341. The nonwoven web is made of bi-component fibers of a polyethylene (PE) and a polyethylene terephthalate (PET). The ratio of PE/PET is about 60/40. The PE/PET bi-component fiber has the dimension of 2d×51 mm. 
     In an alternative preferred embodiment, the nonwoven web is a spunbonded nonwoven web obtainable from Mitsui Petrochemical Industries, Ltd., Tokyo, Japan. The nonwoven web is made of bi-component fibers of a polyethylene (PE) and a polypropylene (PP). The ratio of PE/PP is about 80/20. The PE/PP bi-component fiber has the thickness is approximately 2.3d. 
     The backsheet  26  is preferably positioned adjacent the outer surface of the absorbent core  28  and is preferably joined thereto by any suitable attachment means known in the art. For example, the backsheet  26  may be secured to the absorbent core  28  by a uniform continuous layer of adhesive, a patterned layer of adhesive, or an array of separate lines, spirals, or spots of adhesive. Adhesives which have been found to be satisfactory are manufactured by H. B. Fuller Company of St. Paul, Minn. and marketed as HL-1258. An example of a suitable attachment means comprising an open pattern network of filaments of adhesive is disclosed in U.S. Pat. No. 4,573,986 entitled “Disposable Waste-Containment Garment”, which issued to Minetola et al. on Mar. 4, 1986. Another suitable attachment means comprising several lines of adhesive filaments swirled into a spiral pattern is illustrated by the apparatus and methods shown in U.S. Pat. No. 3,911,173 issued to Sprague, Jr. on Oct. 7, 1975; U.S. Pat. No. 4,785,996 issued to Ziecker, et al. on Nov. 22, 1978; and U.S. Pat. No. 4,842,666 issued to Werenicz on Jun. 27, 1989. Each of these patents are incorporated herein by reference. Alternatively, the attachment means may comprise heat bonds, pressure bonds, ultrasonic bonds, dynamic mechanical bonds, or any other suitable attachment means or combinations of these attachment means as are known in the art. 
     Embodiments of the present invention are also contemplated wherein the absorbent core is not joined to the backsheet  26 , and/or the topsheet  24  in order to provide greater extensibility in the front waist region  46  and the rear waist region  44 . Alternative embodiments are contemplated wherein an additional member, such as a liquid impervious barrier material(s) (not shown), is positioned between the outer surface  64  of the absorbent core  28  and the backsheet  28 . Any such barrier member may or may not be joined to the absorbent core  28 . Further, the backsheet  26  may or may not be joined to any barrier material(s) that are positioned between the backsheet  26  and the absorbent core  28 . 
     In one aspect of the present invention, the backsheet has a hand value of Koshi (Stiffness) of less than about 11.0, a hand value of Shari (Crispness) of from about 5.0 to about 7.0, and a hand value of Fukurami (Fullness and Softness) less than about 0.5. Preferably, the backsheet has a hand value of Koshi of less than about 7.0. In preferred embodiments, the backsheet has a hand value of Shari is from about 5.5 to about 6.5. Preferably, the backsheet has a hand value of Fukurami of less than about 0.1. 
     The hand value of Koshi approximates the feeling attributable to the bending stiffness of the backsheet. The springy property of the backsheet material enhances this feeling. A backsheet having a compact weaving density, which is woven with springy and elastic yarns enhances this feeling. The hand value of Shari approximates the feeling, which results from the crisp and rough surface of the backsheet. This feeling is caused by hard and strongly twisted yarns. The hand value of Fukurami approximates the feeling, which results from the bulky, rich and well formed backsheet. 
     Thus, the backsheet of the present invention has suitable ranges of hand values, which enhances surface smoothness and softness. For example, the backsheet of the invention reduces frictions between the backsheet and the wearer&#39;s skin in order to prevent skin rash at the wearer&#39;s legs. Further, the backsheet of the invention reduces frictions caused between the backsheet and the wearer&#39;s clothes. Thus, the generation of noise can be prevented to improve the wearer&#39;s comfort. 
     In a preferred embodiment, the backsheet has a fuzz level of less than about 0.24 mg/cm 2 , more preferably of less than about 0.14 mg/cm 2 , and most preferably of less than about 0.05 mg/cm 2 . The fuzz level approximates the amount of untangled fibers, which protrude from the surface of the backsheet. Higher fuzz level results in greater skin irritation as well as a greater itching sensation to the skin. The fuzz level relates to the quantity of untangled fibers which protrude from the surface of the backsheet. The fuzz level also corresponds to the propensity of untangled fibers to get removed from the surface of the backsheet. 
     In more preferred embodiments, the backsheet has a mean value of coefficient of friction (MIU) of less than about 0.21, more preferably less than about 0.18. Lower values of MIU result in lower frictions between the backsheet and the wearer&#39;s skin, and between the backsheet and the wearer&#39;s clothes. 
     An especially preferred nonwoven web is a spunbonded nonwoven web, preferably made of bi-component fibers. In preferred embodiments, the spunbonded nonwoven web has a hand value of Koshi of less than about 16.0, a hand value of Shari of from about 0.5 to about 9.5, and a hand value of Fukurami of less than about 5.0. In a preferred embodiment, the spunbonded nonwoven web has a fuzz level of less than about 1.0. 
     These hand values and levels are calculated based on the physical properties which are obtained from the following measurements. The physical properties include 1) Tensile property; 2) Bending property; 3) Surface property; 4) Shearing property; 5) Compression property; and 6) Weight and thickness. These properties include in total sixteen (16) characteristic values or detailed properties as indicated in the Table I. 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE I 
               
               
                   
               
               
                 Property 
                 Symbols 
                 Property 
                 Unit 
                 Remarks 
               
               
                   
               
             
            
               
                 Tensile 
                 LT 
                 linearity of load- 
                 none 
                 LT = 1: completely linear 
               
               
                   
                   
                 extension curve 
                   
                 and 
               
               
                   
                   
                   
                   
                 LT = 0: extremely non-linear 
               
               
                   
                 WT 
                 tensile energy per 
                 gf · 
                 Higher value of WT corresponds to 
               
               
                   
                   
                 unit area 
                 cm/cm 2   
                 higher extensibility. 
               
               
                   
                 RT 
                 tensile resilience 
                 % 
                 RT = 100%: completely elastic 
               
               
                   
                   
                   
                   
                 RT = 0%: completely inelastic 
               
               
                   
                 EM 
                 extensibility 
                 % 
                 Strain at maximum load 
               
               
                   
                   
                   
                   
                 (= 50 gf/cm) 
               
               
                 Bending 
                 B 
                 bending rigidity 
                 gf · 
                 Bending rigidity per unit width of 
               
               
                   
                   
                   
                 cm 2 /cm 
                 fabric. 
               
               
                   
                 2HB 
                 hysteresis of bending 
                 gf · 
                 Hysteresis of bending moment 
               
               
                   
                   
                 moment 
                 cm/cm 
                 observed in the bending moment- 
               
               
                   
                   
                   
                   
                 curvature relationship. A larger 
               
               
                   
                   
                   
                   
                 value of 2HB means a greater 
               
               
                   
                   
                   
                   
                 fabric inelasticity 
               
               
                 Shearing 
                 G 
                 shear stiffness 
                 gf/cm 
               
               
                   
                   
                   
                 degree 
               
               
                   
                 2HG 
                 hysteresis of shear 
                 gf/cm 
               
               
                   
                   
                 force at 0 degree of 
               
               
                   
                   
                 shear angle 
               
               
                 Compression 
                 LC 
                 linearity of 
                 none 
                 LC = 1: completely linear 
               
               
                   
                   
                 compression- 
                   
                 LC = 0: completely non-linear 
               
               
                   
                   
                 thickness curve 
               
               
                   
                 WC 
                 compressional energy 
                 gf · 
                 A larger value of WC corresponds 
               
               
                   
                   
                   
                 cm/cm 2   
                 to higher compressibility. 
               
               
                   
                 RC 
                 compressional 
                 % 
                 RC = 100%: elastic 
               
               
                   
                   
                 resilience 
                   
                 and 
               
               
                   
                   
                   
                   
                 RC = 0%: completely inelastic 
               
               
                 Surface 
                 MIU 
                 coefficient of friction 
                 none 
                 Higher value corresponds to higher 
               
               
                   
                   
                   
                   
                 friction. 
               
               
                   
                 MMD 
                 mean deviation of 
                 none 
                 Higher value corresponds to larger 
               
               
                   
                   
                 MIU 
                   
                 variation of friction. 
               
               
                   
                 SMD 
                 geometrical 
                 μm 
                 Higher value corresponds to 
               
               
                   
                   
                 roughness 
                   
                 geometrically rough surface. 
               
               
                 Weight 
                 W 
                 sample weight 
                 mg/cm 2   
               
               
                 and 
                 T o   
                 sample thickness 
                 mm 
                 Thickness at pressure of 0.5 gf/cm 2   
               
               
                 Thickness 
               
               
                   
               
            
           
         
       
     
     The sixteen characteristic values are obtained by the measurement and analytical methods described in the next section. Similar (although not identical) measurement and analytical methods for fabric are known and described, for example, in the Chapter IV of the text book, by Sueo Kawabata, entitled “The Standardization and Analysis of Hand Evaluation (2nd. Edition)”, published by the Textile Machinery Society of Japan, July 1980. The disclosure of this book is incorporated herein by reference. Based on the sixteen characteristic values obtained from the measurements, the hand values of Koshi, Shari and Fukurami are obtained according to the following analytical methods. The fuzz level is measured by the specific method described in the later section. 
     2. Measurement and Calculation Methods for Hand Values and Fuzz Level 
     1) Tensile Property: 
     The backsheet sample is subjected to applied unidirectional extension stress up to a maximum load of 50 gf/cm and then allowed to return to its initial state. The speed of the deformation is 0.1 mm/s. The effective dimension of the sample is 20 cm in width and 2.5 cm in length (rectangular). As a result, the tensile property curve as shown in  FIG. 4  is obtained by the measurement. The horizontal axis shows the strain (%) and the vertical axis shows the stress (gf/cm). The characteristic values of LT, WT, and RT are calculated as follows: 
         LT =( Sa+Sb )/( Sa+Sb+Sc )  (1)
 
         WT=Sa+Sb   (2)
 
         RT=Sb /( Sa+Sb )  (3)
 
     where Sa, Sb, Sc are defined by the areas shown in  FIG. 4 . 
     2) Bending Property: 
     The deformation mode is obtained by bending the sample between a curvature K=−2.5 cm −1  and K=2.5 cm −1 . The deformation mode is a measure of the force required to bend the sample. The effective dimension of the sample for this measurement is 2.0 cm in length and 1.0 cm in width (rectangular). The sample is bent as shown in  FIGS. 5A and 5B . The bending rate is 0.5 cm −1 /sec. As a result, a bending histeresis curve as shown in  FIG. 6  is obtained. The horizontal axis shows the curvatures K cm −1  and the vertical axis shows the moment M (gf·cm/cm). The values of B and 2HB are calculated as follows: 
         B =( Bf+Bb )/2  (4)
 
     where Bf and Bb are the slopes of the histeresis curves between K=0.5 cm −1  and 1.5 cm −1  and K=−0.5 cm −1  and −1.5 cm −1  respectively. 
       2 HB =(2 HBf+ 2 HBb )/2  (5)
 
     where 2HBf and 2HBb are the histeresis differences at K=0.5 cm −1  and −0.5 cm −1 , respectively. 
     3) Surface Property: 
     To measure the surface roughness of the sample, a pianowire is prepared and bent as shown in  FIGS. 7A and 7B . 5.0 gf (allowance, ±0.5 gf) of the contact force is applied by a spring having a spring constant of 25±1 gf/mm. The natural frequency of the system should be more than 30 Hz when the contactor does not contact the sample. 
     The friction between the surfaces of the sample and a contactor is measured under a constant contact pressure. Surface friction should be measured by using the contactor shown in  FIGS. 8A and 8B . The surface of the contactor is covered by ten parallel and stacked piano steel wires. The ten pieces of the same wires are placed on the surface of specimen. A compression force of 50 gf by dead weight is applied to the surface of the sample through the contactor. 
     In the both of the roughness and friction measurements, the specimen displaced a distance of 2 cm at a constant velocity of 0.1 cm/sec on a smooth steel plate placed horizontally where the tension of the specimen is kept at 5.0 gf/cm (force per unit length) and the contactor is kept its position. The dimension of the plate is shown in  FIG. 9 . The variations of the surface coefficient of friction μ and the sample thickness T that are obtained are shown in  FIGS. 10 and 11 . 
     Consequently, the values of MIU, MMD and SMD are obtained from the following expressions: 
     
       
         
           
             
               
                 
                   
                     MIU 
                     = 
                     
                       
                         1 
                         X 
                       
                        
                       
                         
                           ∫ 
                           0 
                           x 
                         
                          
                         
                           μ 
                            
                           
                              
                             x 
                           
                         
                       
                     
                   
                   , 
                 
               
               
                 
                   ( 
                   6 
                   ) 
                 
               
             
             
               
                 
                   
                     MIU 
                     = 
                     
                       
                         1 
                         X 
                       
                        
                       
                         
                           ∫ 
                           0 
                           x 
                         
                          
                         
                           
                              
                             
                               μ 
                               - 
                               
                                 μ 
                                 ′ 
                               
                             
                              
                           
                            
                           
                              
                             x 
                           
                         
                       
                     
                   
                   , 
                 
               
               
                 
                   ( 
                   7 
                   ) 
                 
               
             
             
               
                 
                   
                     SMD 
                     = 
                     
                       
                         1 
                         X 
                       
                        
                       
                         
                           ∫ 
                           0 
                           x 
                         
                          
                         
                           
                              
                             
                               T 
                               - 
                               
                                 T 
                                 ′ 
                               
                             
                              
                           
                            
                           
                              
                             x 
                           
                         
                       
                     
                   
                   , 
                 
               
               
                 
                   ( 
                   8 
                   ) 
                 
               
             
           
         
       
     
     where μ; frictional force/compressional force 
     μ′; mean value of μ 
     x; displacement of the contactor on the surface of sample 
     X; 2 cm is taken in this measurement 
     T; Thickness of the sample at position x 
     T′; Mean value of T 
     4) Shearing Property: 
     A constant extension force of 5 gf/cm is applied on a longitudinal direction of the sample and then a shear force Fs is applied to the sample plane along the transverse direction of the sample up to the shear angle ø=4° as shown in  FIG. 12 . Then, the sample shear deformation is recovered by reducing the shear angle back to zero. The effective dimension of the sample is 20 cm in width and 5 cm in length. The relationship between Fs and ø that is obtained is shown in  FIG. 13 . The value of 2HG is obtained from the hysteresis curve at ø=0°. The value of G is calculated as follows: 
         G =( Gf+Gb )/2  (9)
 
     where Gf and Gb are the average slopes of the curve between ø=0.5° and 5° and between ø=−0.5° and −5° respectively. 
     5) Compression Property: 
     For this test, the effective dimension of the sample is 2.5 cm long and 2.0 cm in width. The longitudinal direction of the sample is taken along either warp or weft direction. 2 cm 2  of a circled area of the sample is compressed by two circular-plates of steel having 2 cm 2  area ( FIG. 14 ). The velocity of the compression is 20 micron/sec and when the pressure reaches 10 g/cm 2 , the recovery process is measured at the same velocity. The values of LC, WC and RC are obtained by the following expressions: 
     
       
         
           
             
               
                 
                   LC 
                   = 
                   
                     WC 
                     / 
                     WOC 
                   
                 
               
               
                 
                   ( 
                   10 
                   ) 
                 
               
             
             
               
                 
                   WC 
                   = 
                   
                     
                       ∫ 
                       Tm 
                       To 
                     
                      
                     
                       P 
                        
                       
                          
                         T 
                       
                     
                   
                 
               
               
                 
                   ( 
                   11 
                   ) 
                 
               
             
             
               
                 
                   RC 
                   = 
                   
                     
                       WC 
                       ′ 
                     
                     / 
                     WC 
                   
                 
               
               
                 
                   ( 
                   12 
                   ) 
                 
               
             
           
         
       
     
     where 
     T; Thickness of the sample (cm). 
     To; Thickness of the sample at a pressure of 0.5 gf/cm 2 . 
     Tm; Thickness of the sample at maximum pressure Pm which is:
         Pm=10 gf/cm 2          

         WOC;=Pm ( To−Tm )/2  (13)
 
     WC′; Recovering energy given by the pressure of the recovering process, P′ such as 
     
       
         
           
             
               
                 
                   
                     WC 
                     ′ 
                   
                   = 
                   
                     
                       ∫ 
                       Tm 
                       To 
                     
                      
                     
                       
                         P 
                         ′ 
                       
                        
                       
                          
                         T 
                       
                     
                   
                 
               
               
                 
                   ( 
                   14 
                   ) 
                 
               
             
           
         
       
     
     6) Weight and Thickness: 
     The value of T mm is measured as the thickness when the compressional property is measured (P=0.5 gf/cm 2 ). The value of W g/m 2  is measured as the weight per unit area of the sample. 
     (2) Calculation of Hand Values 
     The hand values of Koshi, Shari and Fukurami are obtained from the following expression (15) by applying the sixteen characteristic values obtained from the measurements. The calculation using the expression (15) is conducted according to the Knit High Sensivity Condition (KN-403-KTV). 
     
       
         
           
             
               
                 
                   HV 
                   = 
                   
                     Co 
                     + 
                     
                       
                         ∑ 
                         16 
                         
                           i 
                           = 
                           1 
                         
                       
                        
                       
                         { 
                         
                           
                             Ci 
                             · 
                             
                               
                                 ( 
                                 
                                   Xi 
                                   - 
                                   
                                     Xi 
                                     ′ 
                                   
                                 
                                 ) 
                               
                               / 
                               σ 
                             
                           
                            
                           
                               
                           
                            
                           i 
                         
                         } 
                       
                     
                   
                 
               
               
                 
                   ( 
                   15 
                   ) 
                 
               
             
           
         
       
     
     where HV is the hand value. 
     The numbers and constants to be applied to the equation are indicated in the Tables II and III. 
     
       
         
           
               
               
               
               
               
               
             
               
                   
                 TABLE II 
               
               
                   
                   
               
               
                   
                 Property 
                 i 
                 Xi 
                 Xi′ 
                 i 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                   
                   
                 0 
                   
                   
                   
               
               
                   
                 Tensile 
                 1 
                 LT 
                 0.7756 
                 0.0679 
               
               
                   
                   
                 2 
                 log WT 
                 0.6808 
                 0.2557 
               
               
                   
                   
                 3 
                 log RT 
                 1.5952 
                 0.0639 
               
               
                   
                 Bending 
                 4 
                 log B 
                 −1.6441 
                 0.3288 
               
               
                   
                   
                 5 
                 log 2HB 
                 −1.5180 
                 0.3213 
               
               
                   
                 Shearing 
                 6 
                 log 2G 
                 −0.4000 
                 0.1276 
               
               
                   
                   
                 7 
                 log 2HG 
                 0.0444 
                 0.1486 
               
               
                   
                   
                 8 
                 log 2HG5 
                 0.0444 
                 0.1486 
               
               
                   
                 Compression 
                 9 
                 LC 
                 0.6337 
                 0.0692 
               
               
                   
                   
                 10 
                 log WC 
                 −0.9937 
                 0.1526 
               
               
                   
                   
                 11 
                 RC 
                 38.1224 
                 5.6815 
               
               
                   
                 Surface 
                 12 
                 log HIU 
                 −0.5952 
                 0.0861 
               
               
                   
                   
                 13 
                 log HMD 
                 −1.5999 
                 0.2018 
               
               
                   
                   
                 14 
                 log SMD 
                 0.9280 
                 0.1999 
               
               
                   
                 Weight and 
                 15 
                 log T 
                 0.0638 
                 0.1361 
               
               
                   
                 Thickness 
                 16 
                 W 
                 17.3383 
                 5.0040 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
               
               
               
             
               
                   
                 TABLE III 
               
             
            
               
                   
                   
               
               
                   
                   
                   
                 For 
                   
                   
                   
               
               
                   
                 For Koshi 
                   
                 Fukurami 
                   
                 For Shari 
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                 i 
                 Ci 
                 i 
                 Ci 
                 i 
                 Ci 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                 0 
                 4.4473 
                 0 
                 4.5531 
                 0 
                 4.8480 
               
               
                   
                 6 
                 0.9934 
                 9 
                 −0.1760 
                 14 
                 1.1399 
               
               
                   
                 7 
                 −0.0264 
                 10 
                 1.9067 
                 13 
                 0.1485 
               
               
                   
                 8 
                 0.4165 
                 11 
                 0.7942 
                 12 
                 −0.1527 
               
               
                   
                 4 
                 0.5064 
                 15 
                 −0.0193 
                 10 
                 −0.5692 
               
               
                   
                 5 
                 0.3654 
                 16 
                 0.4399 
                 11 
                 −0.2623 
               
               
                   
                 15 
                 −0.1568 
                 12 
                 −0.1182 
                 9 
                 0.1401 
               
               
                   
                 16 
                 0.2789 
                 13 
                 −0.4141 
                 4 
                 0.5975 
               
               
                   
                 1 
                 −0.2437 
                 14 
                 0.1194 
                 5 
                 −0.1113 
               
               
                   
                 2 
                 −0.1740 
                 1 
                 −0.0169 
                 1 
                 0.1786 
               
               
                   
                 3 
                 0.0931 
                 2 
                 0.2347 
                 3 
                 0.0492 
               
               
                   
                 9 
                 −0.1255 
                 3 
                 −0.1000 
                 2 
                 −0.0307 
               
               
                   
                 10 
                 0.1252 
                 6 
                 −0.3254 
                 16 
                 −0.1966 
               
               
                   
                 11 
                 0.0119 
                 7 
                 −0.4482 
                 15 
                 −0.0113 
               
               
                   
                 12 
                 −0.0125 
                 8 
                 0.8427 
                 8 
                 0.1770 
               
               
                   
                 13 
                 0.1037 
                 4 
                 −0.2441 
                 6 
                 −0.0284 
               
               
                   
                 14 
                 0.0276 
                 5 
                 0.1412 
                 7 
                 0.0135 
               
               
                   
                   
               
            
           
         
       
     
     (3) Measurement and Analysis Equipment 
     An example of preferred measurement and analysis equipment is the type KES FB1-FB4 which is available form Kato Tech Co., LTD., Kyoto Japan. The backsheet sample to be used by this equipment is a square sheet of 20 cm×20 cm. The measurement and analysis are conducted on at least three (3) samples, more preferably at least ten (10) samples. 
     (4) Fuzz Level Measurement 
     To measure the quantity of untangled fibers that protrude from the surface of the sample, the face of the sample  12  is rubbed against the face of sandpaper  14  for 29 seconds at 0.7 Hz to cut or loosen the untangled fibers  16 . 18.1 gf/cm 2  of pressure is applied to the sample  12 . An example of the equipment is shown in  FIG. 16 . The cut fibers produced by this action are collected by a removal tape and quantified with an analytical balance. The fuzz level is defined as the weight of the fibers collected per unit area (mg/cm 2 ). 
     An example of equipment available is Sutherland Ink Rub Tester. 18.1 gf/cm 2  of pressure is applied to the sample. This apparatus abrades a 6.5 cm×15 cm piece of sample with a 15 cm×5.1 cm piece of sandpaper (Matelite K224 Cloth Sandpaper Grit 320-J, Norton Co., Troy, N.Y.). The rub cycle is 20 times at 0.7 cycle/sec. The fibers (fuzz) are removed using two 15 cm×5.1 cm pieces of removal tape (3M Scotch Carton Sealing Tape, J A Kindel, Cincinnati, Ohio) from both the sandpaper and sample. 
     3. Examples 
     Example I 
     23 g/m 2  of a carded nonwoven web obtainable from Havix Co., LTD., Gifu, Japan as E-2341 is prepared. The nonwoven web is made of bi-component fibers of a polyethylene (PE) and a polyethylene terephthalate (PET). The nonwoven web is joined to 25 g/m 2  of a microporous polyethylene (PE) film obtainable from Mitsui Toatsu Chemicals, Inc., Nagoya, Japan as Espoir No. by using 5 g/m 2  of a hotmelt adhesive obtainable from Nitta Findley Co., Ltd., Osaka, Japan as H-2476-01 with a meltblown pattern (Nordson K.K., Tokyo, Japan). The PE/PET bi-component fiber has the dimension of 2d×51 mm. The ratio of PE/PET is about 60/40. The open time and temperature of hotmelt adhesive before the application is 0.5 sec and 160° C., respectively. 
     This backsheet sample has hand values of Koshi, Shari, and Fukurami are 10.6, 0.2, and 6.3, respectively. The fuzz level is 0.31 mg/cm 2 . The mean value of coefficient of friction (MIU) is 0.19. 
     Example II 
     23 g/m 2  of a spunbonded nonwoven web obtainable from Mitsui Petrochemical Industries, Ltd., Tokyo, Japan is prepared. The nonwoven web is made of bi-component fibers of a polyethylene (PE) and a polypropylene (PP). The nonwoven web is joined to 25 g/m 2  of a microporous polyethylene (PE) film obtainable from Mitsui Toatsu Chemicals, Inc., Nagoya, Japan as Espoir No. by using 1.5 g/m 2  of a hotmelt adhesive obtainable from H.B. Fuller Japan Co., Ltd., Osaka, Japan as JM-6064 with a random dot pattern (Porous Coating, Nordson K.K., Tokyo, Japan). The PE/PP bi-component fiber has the thickness of approximately 2d. The ratio of PE/PP is about 80/20. The open time and temperature of hotmelt adhesive before the application is about 0.5 sec and about 160° C., respectively. The mean value of coefficient of friction (MIU) is 0.21. 
     This backsheet sample has hand values of Koshi, Shari, and Fukurami are 9.6, −2.4, and 6.6, respectively. The fuzz level is 0.24 mg/cm. The spunbonded nonwoven web has a tensile strength of 185 gf/cm at 12.7 cm/min of sample displacement speed (Model 4301: Instron Japan Co., Ltd., Kanagawa, Japan). 
     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.