Absorbent article with surface structure

Abstract: There is disclosed an absorbent article including: a surface structure having a liquid-permeable surface sheet located on a liquid-receiving side; a back sheet; and an absorbent core sandwiched between the surface structure and the back sheet. In an area including at least a centerline extending in a longitudinal direction of the absorbent article, the surface sheet is corrugated to form recesses and ridges extending in the longitudinal direction and alternating with each other in a transverse direction perpendicular to the longitudinal direction. The ridges are given an elastically shrinking function in the longitudinal direction at least at their crests or vicinities thereof so that the surface structure is formed into a curved shape. The surface structure thus curved can fit the shape of a crotch. Therefore, the liquid is hard to flow in the transverse direction to prevent the leakage.

Description: The present invention relates to an absorbent article such as a disposable diaper, a pad for the incontinence of urine or a sanitary napkin and, more particularly, it relates to an absorbent article including a surface structure having an excellent fittingness on a body. The absorbent article of the prior art such as the disposable diaper, the pad for the urinary incontinence or the sanitary napkin generally includes: a liquid-permeable top sheet disposed on the liquid-receiving, inner side; a liquid-impermeable back sheet disposed on the outer side; and an absorbent core made of pulp and a highly absorbent polymer (or super absorbent polymer: SAP) and sandwiched between the two sheets. In such an absorbent article, a structure has been investigated for improving the fittingness on a urinary organ and thereabout, when applied to a crotch, to prevent excreted liquid such as urine or menstrual blood from leaking transversely. For example, there has been practiced a structure, in which a relatively bulky cushion layer made of a hydrophilic fiber layer is disposed on the liquid-receiving side of the absorbent core, or a structure in which an absorbent material layer smaller than the absorbent core is disposed on the liquid-receiving side of the absorbent and such a cushion layer as above is further disposed on the absorbent material layer. In another structure, gathers for preventing the transverse leakage are disposed on two side edges of the absorbent core. However, the aforementioned absorbent article provided with the cushion layer cannot cover the individual differences in the shape of the crotch reliably at all times. Especially, the disposable diaper or the pad for the urinary incontinent for taking care of old people frequently fails to fit the crotch. This is because the old people are seriously different among the individuals in the width of the crotch, in the flesh of the crotch, abdomen or hip or in the flabbiness or wrinkles of the skin, as compared with infants. If the absorbent article fails to fit the crotch, the excreted liquid will easily leak along the skin to the outside of the absorbent article to wet the wears or bedclothes. This problem is more serious for the old people who excrete far more liquid for one piss than the infants. When such an absorbent article unfitted for the crotch is worn, moreover, irregular wrinkles are formed on the liquid-receiving side of the absorbent article to make it harder for the absorbent article to absorb the excreted liquid. Against these problems, there exists an absorbent article which is curved to fit the crotch by providing transverse leakage preventing gathers on two side edges of an absorbent core so that the absorbent core may follow the gathers. However, even in this absorbent article, because the central portion of the absorbent core is less curved than the side edges thereof, the absorbent core is difficult to fit the whole crotch, thereby to leave gaps between the absorbent core and the crotch. As a result, a large amount of excreted liquid may move transversely through the gaps so that its leakage cannot be prevented by the transverse leakage preventing gathers. WO-A-9829074 describes an absorbent article comprising: a surface structure having a liquid-permeable surface sheet located on a liquid-receiving side; a back sheet; and an absorbent core sandwiched between the surface structure and the back sheet. In an area including at least a centreline extending in a longitudinal direction of the absorbent article, the surface sheet is corrugated to form recesses and ridges extending in the longitudinal direction and alternating with each other in a transverse direction perpendicular to the longitudinal direction, and the ridges are given an elastically shrinking function in the longitudinal direction at least at their crests or vicinities thereof so that the surface structure is formed into a curved shape. The surface structure includes a liquid-permeable support sheet located between the surface sheet and the absorbent core, and the support sheet is bonded to the surface sheet at an interval in the transverse direction to thereby form the recesses. It is an object of the present invention to provide an improved absorbent article. The invention provides an absorbent article comprising: a surface structure having a liquid-permeable surface sheet located on a liquid-receiving side; a back sheet; and an absorbent core sandwiched between the surface structure and the back sheet, wherein, in an area including at least a centreline extending in a longitudinal direction of the absorbent article, the surface sheet is corrugated to form recesses and ridges extending in the longitudinal direction and alternating with each other in a transverse direction perpendicular to the longitudinal direction, and the ridges are given an elastically shrinking function in the longitudinal direction at least at their crests or vicinities thereof so that the surface structure is formed into a curved shape; and wherein the surface structure includes a liquid-permeable support sheet located between the surface sheet and the absorbent core, and the support sheet is bonded to the surface sheet at an interval in the transverse direction to thereby form the recesses; characterised in that a cushion layer is provided inside of the ridges such that the cushion layer is sandwiched between the surface sheet and the support sheet. Preferably, ridges in a center region including the longitudinally extending centreline are different in height from other ridges in two side regions outside of the center region. Preferably, cover sheets are provided to cover longitudinal end portions of the ridges. Embodiments of the invention are described below with reference to the accompanying drawings in which: Fig. 1 is a partially sectional, perspective view showing an absorbent article according to a first embodiment of the invention; Fig. 2 is a sectional view of the absorbent article shown in Fig. 1; Fig. 3 is an explanatory view showing a curved state of a surface structure of the invention; Fig. 4 is a partially sectional, perspective view showing an absorbent article according to a second embodiment of the invention; Fig. 5 is a sectional view showing an absorbent article according to a third embodiment of the invention; and Fig. 6 is a top plan view showing an example in which a disposable diaper is constructed of the absorbent article of the invention. Fig. 1 is a partially sectional, perspective view showing an absorbent article according to a first embodiment of the invention; Fig. 2 is a sectional view of the absorbent article of the invention; and Fig. 3 is an explanatory view showing a state in which a surface structure is curved. In the following, a direction X is a transverse (or widthwise) direction of the absorbent article, and a direction Y is a longitudinal (or lengthwise) direction of the absorbent article. As shown in Figs. 1 and 2, an absorbent article 1 is backed on a back side of an absorbent core 2 with a back sheet and is surfaced on a liquid-receiving side of the absorbent core 2 with a surface structure 4. This surface structure 4 includes a surface sheet 5 and a support sheet 6, and these surface sheet 5 and support sheet 6 and the back sheet 3 are adhered together with an adhesive such as hot melt adhesive in a peripheral region A where no absorbent core 2 is present. When the surface sheet 5, the support sheet 6 and the back sheet 3 contain thermoplastic fibers, they may be thermally fused together in the aforementioned peripheral region A. Alternatively, it may be possible that only the support sheet 6 and the back sheet 3 are bonded (adhered or fused) together in the peripheral region A, while the surface sheet 5 is bonded to the support sheet 6 at a position inside of the peripheral region A (i.e. at a positon where the absorbent core 2 is present). The absorbent core 2 is constructed by enveloping either pulverized pulp or a mixture of pulverized pulp and highly absorbent polymer (or super absorbent polymer: SAP) with an absorbent sheet such as tissue paper. The SAP can be made of polyacrylic acid, sodium polyacrylate, polyacrylamide, polyacrylonitrile, polyvinyl alcohol, an additional polymer of maleic anhydride, a polyether, a condensed polymer, a polysaccharide such as starch or cellulose, a protein such as collagen, or the like. Examples of the SAPs include: a cross-linked compound of sodium polyacrylate, a graft copolymer of starch having sodium polyacrylate or a graft copolymer of cellulose having polyacrylonitrile chains. The back sheet 3 may be liquid-impermeable and made of, for example, an olefin resin sheet. When the absorbent article 1 is used as a disposable diaper or sanitary napkin, the back sheet 3 is preferably made gas-permeable. However, the back sheet 3 of the absorbent article 1 of the invention may be made liquid-permeable, if it is used to be worn inside another absorbent material in which excessive liquid will permeate and will be absorbed. The aforementioned surface sheet 5 and support sheet 6 composing the surface structure 4 are preferably made of a point-bond, air-through, spun-bond or spun-lace non-woven fabric. This non-woven fabric is formed of, for example, hydrophilized hydrophobic fibers or hydrophilic fibers. The "hydrophilized hydrophobic fibers" as used herein means hydrophobic fibers subjected to hydrophilic treatment. In this hydrophilic treatment, a hydrophobic fiber is made hydrophilic by treating it with a surfactant; by chemically binding a chemical substance such as a monomer or a polymer having a hydrophilic group thereto; by subjecting it to plasma processing; by kneading it with a chemical substance having a hydrophilic group; or by treating its surface to have a profiled section. The surface sheet 5 and support sheet 6 may be made of a resin film having a number of apertures. This resin film can be made of polyethylene (PE) or the like. As in Fig. 2, the surface sheet 5 is bonded to the support sheet 6 at an interval (or pitch distance) 7p in the transverse direction. These bonded portions are designated by 7a. By forming these bonded portions 7a, the surface sheet 5 is corrugated to have recesses 7 and ridges 8. That is, the surface sheet 5 is deformed to have the ridges (or bulges) 8 rising toward the wearer, between the bonded portions 7a. The ridges 8 and the recesses 7 are extended in the longitudinal direction (or the direction Y) to form a plurality of parallel rows. The bonding between the surface sheet 5 and the support sheet 6 for forming the recesses 7 can be performed by adhesion with an adhesive such as hot melt adhesive. Alternatively, the surface sheet 5 and the support sheet 6 may be thermally fused together when they contain thermoplastic fibers. The bonded portions 7a may be formed in longitudinally continuous lines. Alternatively, they may be formed to extend intermittently in the longitudinal direction. For example, if an adhesive of the hot melt type is applied to the surface of the support sheet 6 in a spiral pattern or the like and the surface sheet 5 is adhered to the support sheet 6, the bonded portions 7a can be formed intermittently in the longitudinal direction as above. When the bonded portions 7a are thus intermittently formed, the excreted liquid such as urine fed to the recesses 7 readily penetrates from the bottoms of the recesses 7 into the absorbent core 2. At the crests 8t of the ridges 8, there are arranged elastic members 10, each extending in the longitudinal direction. These elastic members 10 are adhered to the inner side of the surface sheet 5, i.e., to the face of the surface sheet 5 on the side of the absorbent core 2, while being elongated (or pulled and stretched) in the longitudinal direction. Therefore, after such adhesion, the surface sheet 5 longitudinally shrinks at the crests 8t owing to the elastically shrinking function of the elastic members 10, so that the whole surface structure 4 is curved as shown in Fig. 3. As a result, the absorbent core 2 is also curved. The elastic members 10 may be made of any elastic material such as natural rubber, synthetic rubber or stretch non-woven fabric (i.e., non-woven fabric having elasticity). Here, the surface sheet 5 per se may be made of such stretch non-woven fabric to have an elastically shrinking function in the longitudinal direction. In this case, the elastic members 10 need not be provided to the surface sheet 5. Therefore, the surface structure 4 can be easily manufactured. The height of the ridges 8, that is, the height size 8h (as referred to Fig. 2) from the surface of the support sheet 6 to the crests 8t of the ridges 8 is preferably from 5 mm or more to 50 mm or less. Within this range, the liquid-receiving side of the absorbent article can fit the crotch of a wearer, even if the absorbent article is used for taking care of old people who are seriously different among the individuals in body contours. More preferably, the height size 8h is from 10 mm or more to 30 mm or less. In the surface structure 4, moreover, there may be provided a cushion layer 9 of a hydrophilic material inside of the ridges 8, i.e., between the surface sheet 5 and the support sheet 6, as shown in Figs. 1 and 2. With this cushion layer 9, the elastcity of the ridges 8 is so enhanced that the shape of the ridges 8 can be maintained securely when they come into contact with the wearer. In this case, therefore, the surface structure 4 will fit the crotch more closely. In stead of providing the cushions layer 9, however, the inside of the ridges 8 may be vacant. That is, the space between the surface sheet 5 and the support sheet 6 may be left as clear gaps. The hydrophilic material for the cushion layer 9 can be exemplified by various materials. For example, use can be made of hydrophilized hydrophobic fibers of polyethylene, polypropylene, nylon or polyester, hydrophilized hydrophobic composite fibers of polyester and polyethylene, or hydrophilic fibers such as rayon. As described before, the term "hydrophilized hydrophobic fibers" means hydrophobic fibers subjected to hydrophilic treatment. Such fibers may be long fibers (or filaments) prepared in the form of tow. Or else, use can be made of a split yarn or strip-shaped materials, which are originally hydrophilic or originally hydrophobic but subjected to hydrophilic treatment. The split yarn is produced by finely cutting a resin film into the net-like shape, in which short fibers extend generally in one direction. The strip-shaped materials are produced by cutting a resin film or non-woven fabric into strips. Alternatively, the material may be exemplified by either a non-woven fabric, such as air-through non-woven fabric of hydrophilic fibers or hydrophobic fibers subjected to hydrophilic treatment, which is bulky and has a low density, or a web of opened fibers having a relatively short length (e.g., hydrophilic fibers or hydrophobic fibers subjected to hydrophilic treatment). Preferably, the cushion layer 9 is bulky and readily permeable to liquid and can be readily elastically recovered (or restored) from its pressurized state. Therefore, it is preferable that the cushion layer 9 has a density of 0.4 g/cm 3 or less and the fibers constituting the cushion layer 9 has a fineness of 1 denier or more. Fig. 4 is a perspective view showing an absorbent article 1B of a second embodiment of the invention. In this absorbent article 1B, the ridges 8 are made different. Hereinafter, the detailed description of the portions having the same constructions as those of the first embodiment will be omitted by designating them by the common reference numerals. In the embodiment shown in Fig. 4, the ridges 8 are made higher, as indicated by 8a, in the vicinity of the central region and made lower, as indicated by 8b, in the two side regions. Thus, the fittingness on the crotch or urinary organ is further enhanced by the difference of the height between the ridges 8a and 8b. In this case, the ridges 8a preferably have a height of about 25 mm whereas the ridges 8b preferably have a height of about 15 mm. This embodiment may be modified such that the ridges are gradually lowered from ridges 8c and 8c in the central region to ridges 8d and 8d in the two side regions. On the contrary, the ridges 8a in the vicinity of the central region may be made lower whereas the ridges 8b in the two side regions may be made higher. In this case, the ridges 8a preferably have a height of about 5 mm whereas the ridges 8b preferably have a height of about 15 mm. Alternatively, the ridges 8 may be made gradually higher from the central region to the two side regions. Fig. 5 is a sectional view showing an absorbent article 1C of a third embodiment of the invention. In Fig. 5, two elastic members 10a and 10b are disposed at the crest 8t of each ridge 8. Between two adjacent ridges 8 and 8, on the other hand, two bonded portions 7a and 7a are provided to form one recess 7. That is, in each recess 7, two continuous or intermittent lines of the bonded portions 7a extend parallel to each other. Fig. 6 is a top plan view showing an open type disposable diaper with its liquid-receiving side being located on this side, as a specific embodiment of the absorbent article 1, 1B or 1C of the invention. The disposable diaper, as constructed of the absorbent article of the invention, has: an intermediate portion 21 to be applied to the crotch of a wearer; a front portion 22 to be applied to the abdomen thereof; and a rear portion 23 to be applied to the hip thereof. In the disposable diaper shown in Fig. 6, the back sheet 3 and the support sheet 6 are given an hour glass shape, and the absorbent core 2 (indicated by dotted lines in Fig. 6) is also given an hour glass shape. The transversely constricted portions of those hour glass shapes provide the aforementioned intermediate portion 21. In the peripheral region A where the absorbent core 2 is not present, the support sheet 6 and the back sheet 3 are bonded to each other to secure the absorbent core 2 therebetween. In the disposable diaper shown in Fig. 6, the surface sheet 5 shown in Figs. 1 and 2 is present only in the widthwise center on the liquid-receiving side to form the ridges 8 and the recesses 7. The cushion layer 9 is disposed between the surface sheet 5 and the support sheet 6. The area where the ridges 8 and the recesses 7 are present is in a rectangular shape extending from the front portion 22 through the intermediate portion 21 to the rear portion 23 in the longitudinal direction and over two side regions 31 and 31 across a centreline 30 in the transverse direction. That is, as shown in Fig. 6, the ridges 8 and the recesses 7 are present in the area having a length almost equal to that of the absorbent core 2 and a width almost equal to that of the intermediate portion 21 of the absorbent core 2. The area may be modified variously according to the applications. In the disposable diaper of Fig. 6, the crests 8t of the ridges 8 of the surface sheet 5 are provided with the elastic members 10 for allowing the disposable diaper to be curved in its entirety by their elastic shrinking forces. The elastic members 10 may be provided either all over the ridges 8 in the longitudinal direction or only over the intermediate portion 21 in the longitudinal direction. It may be also possible that not all but some of the ridges 8 are provided with the elastic members 10. In order to make the curvature of the surface structure proper for the invention, the elastic members 10 are preferably provided over at least 10% of the entire length L1 of the absorbent article 1. However, the elastic members 10 should not be limited to a continuous length of 10% or more but may be provided partially, for example, at two portions of 5 % or more of the entire length L1. The portion requiring the curvature is different for targets of application. For a baby or child, for example, it is preferable that not only the intermediate portion 21 but also both the front portion 22 and the rear portion 23 are curved to fit the round abdomen and hip. For an old wearer, the front portion 22 need not be curved. Thus, the portion to be curved is properly adjusted. The ridges 8 of the surface structure 4 are covered at their opposite end portions 8e and 8e with cover sheets 11 and 11, as shown in Fig. 6. Preferably, each cove sheet 11 has a width larger than that of the area where the ridges 8 are formed, and is bonded to the support sheet 6 with a C-shaped bonded portion 11b to be opened toward the intermediate portion 21. That is, for forming a pocket, it is preferable that each cover sheet 11 is not bonded to the support sheet 6 on the side of the intermediate portion 21. When the excreted liquid moves along the ridges 8, it flows to the front portion 22 or the rear portion 23 of the absorbent article 1 and may further flow to the end portions 1 e and 1e of the absorbent article 1. With the cover sheets 11, however, the longitudinal flows are stopped and sealed by the pockets so that no excreted liquid leaks from the end portions 8e of the ridges 8. Moreover, the cover sheets 11 hide the end portions 8e of the ridges 8 to provide a beautiful appearance. The cover sheets 11 are preferably made of a hydrophobic sheet having a basis weight (this may be referred to as "METSUKE" in Japanese measuring unit) of 20 g/m 2 or more, such as a spun-bond non-woven fabric, a point-bond non-woven fabric, a non-woven fabric laminated with polyethylene, or a film. The absorbent article of the invention can be used as not only a disposable diaper and an incontinent pad but also a sanitary napkin. In this case, the entire shape of the absorbent article can be variably modified according to the applications. For example, it may be modified to have a rectangular top plan shape. As has been described hereinbefore, the absorbent article of the invention can bring its surface structure into close contact with the crotch to prevent the leakage. Moreover, the absorbent article having the ridges of the invention can be freely deformed according to the individual differences of the crotch so that it can fit the skin of the wearer to prevent the leakage more. In the foregoing specification, the invention has been described in relation to preferred embodiments and many details have been set forth for the purpose of illustration. It will be apparent to those skilled in the art that the invention is susceptible to additional embodiments and that certain of the details described herein can be varied considerably whilst still being within the scope of the invention, as defined by the claims. Further, 'comprises/comprising' when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

Claims: An absorbent article comprising: a surface structure (4) having a liquid-permeable surface sheet (5) located on a liquid-receiving side; a back sheet (3); and an absorbent core (2) sandwiched between the surface structure and the back sheet, wherein, in an area including at least a centreline extending in a longitudinal direction of the absorbent article, the surface sheet is corrugated to form recesses (7) and ridges (8) extending in the longitudinal direction and alternating with each other in a transverse direction perpendicular to the longitudinal direction, and the ridges are given an elastically shrinking function in the longitudinal direction at least at their crests or vicinities thereof so that the surface structure is formed into a curved shape; and wherein the surface structure (4) includes a liquid-permeable support sheet (6) located between the surface sheet (5) and the absorbent core (2), and the support sheet is bonded to the surface sheet at an interval in the transverse direction to thereby form the recesses; characterised in that a cushion layer (9) is provided inside of the ridges (8) such that the cushion layer is sandwiched between the surface sheet (5) and the support sheet (6). An absorbent article according to Claim 1, wherein elastic members (10) extending in the longitudinal direction are attached to the crests (8) of the ridges of the surface sheet to thereby give the elastically shrinking function. An absorbent article according to Claim 1 or 2, wherein ridges (8a) in a center region including the longitudinally extending centreline are different in height from other ridges (8b) in two side regions outside of the center region. An absorbent article according to any preceding claim, wherein cover sheets (11) are provided to cover longitudinally end portions of the ridges (8).

Inventors: FUJIOKA YOSHIHISHA, WADA ICHIRO, FUJIOKA, YOSHIHISHA, WADA, ICHIRO
Applicants: UNI CHARM CORP, UNI-CHARM CORPORATION
Application year: 2000
Main classification: A61F13
IPC codes: A61F5, A61F13