JP2019201691A - Absorbent article - Google Patents

Abstract

To provide an absorbent article capable of suppressing reduction of fitting property to a skin even when an absorber is expanded.SOLUTION: An absorbent article comprises: a back sheet 17 formed of a moisture permeable sheet which is stretchable in a cross direction; a liquid permeable top sheet 19 provided closer to a skin side relative to the back sheet 17; and an absorber 18 provided between the top sheet 19 and the back sheet 17. The back sheet 17 comprises a first region 22A where the absorber 18 exists, and second regions 22B each of which protrudes from the absorber 18 in both sides of the first region 22A in a width direction. A second stretchable force of the second region 22B is twice or three times of a first stretchable force of the first region 22A. A moisture transmission of the back sheet 17 is 2,000 or 15,000 g/m24hr (JIS Z-208).SELECTED DRAWING: Figure 2

Description

  The present invention relates to an absorbent article including a back sheet located on the opposite side of the wearer's skin.

  Disposable diapers and urine pads are known as absorbent articles. These absorbent articles are generally composed of a liquid-impermeable back sheet, a liquid-permeable top sheet, and an absorbent body disposed between the top sheet and the back sheet. And the absorber at the time of wear hold | maintains liquids, such as urine which is excrement, via a top sheet, and the back sheet has suppressed that a liquid leaks outside the absorbent article. In the absorbent article, the longitudinal direction is the front-rear direction, and the direction intersecting the front-rear direction is the width direction. And such an absorbent article is provided with the gathers comprised by the sheet | seat thread-like elastic member, and the sheet | seat which pinches | interposes an elastic member around a trunk | drum or a leg (refer patent document 1).

Japanese Patent Laid-Open No. 2018-023760

  By the way, when the absorbent body absorbs moisture such as excreta, the fluff pulp and the superabsorbent polymer expand and the volume increases. Therefore, in the absorbent article, there is a possibility that the fit to the skin is deteriorated due to the expansion of the absorbent body.

  An object of this invention is to provide the absorbent article which made it possible to suppress the fall of the fit with respect to skin even if an absorber expand | swells.

  An absorbent article for solving the above problems is a back sheet composed of a moisture-permeable stretch sheet that stretches at least in the front-rear direction of the absorbent article, and a liquid permeability that is located closer to the wearer's skin than the back sheet. A top sheet and an absorbent body positioned between the top sheet and the back sheet.

  According to the said structure, since the moisture-permeable stretch sheet is used for the back sheet, even if an absorber expand | swells, a back sheet expands according to it. Therefore, even after the absorbent body has expanded, it is possible to suppress a decrease in the fit to the skin.

In the above absorbent article, the moisture permeability of the back sheet is preferably 2,000 to 15,000 g / m ² 24 hr (JIS Z-208). According to the said structure, the stuffiness etc. between a wearer and an absorbent article can be suppressed.

  In the absorbent article, the backsheet has a first region where the absorber is present in a width direction intersecting the front-rear direction, and a first position where the backsheet protrudes from the absorber on both sides of the first region. It is preferable that the second stretch force in the front-rear direction of the second region is larger than the first stretch force in the front-rear direction of the first region. According to the said structure, a leg gather can be comprised in a 2nd area | region.

  The said absorbent article WHEREIN: It is preferable that the 2nd stretching force in the said front-back direction of the said 2nd area | region is 2 to 3 times with respect to the 1st stretching force in the said front-back direction of the said 1st area | region. According to the said structure, the 2nd expansion-contraction force in the said front-back direction of 2nd area | region can be made comparable as the expansion-contraction force of the elastic member conventionally used for leg gathers. Thereby, the part of the 2nd field can be raised firmly as a leg gather.

  The absorbent article further includes a cover sheet that is located on the opposite side of the skin side with respect to the back sheet, and that overlaps the first region and the second region, and the cover sheet extends in the front-rear direction. In the width direction that intersects with each other, it is preferable not to include a folded portion that is folded in the direction of the center line in the width direction and extends to the second region. According to the said structure, the structure which folds a cover sheet | seat and pinches | interposes and fixes an elastic member conventionally is unnecessary. Therefore, production efficiency can be improved.

  The absorbent article further comprises a front body that covers the abdomen of the wearer and a back body that covers the back of the wearer, and the backsheet, the topsheet, and the absorber include the front body and the It is an absorptive main body which comprises the crotch part between back body parts, and it is preferable that a said 2nd area | region comprises a leg gather. According to the said structure, the diaper provided with the leg gather can be comprised.

  In the absorbent article, the first region and the second region are separate sheet elements, and the back sheet includes a first sheet element constituting the first region and a second region constituting the second region. The sheet element is joined to the sheet element. According to the above configuration, the first region having the first stretching force and the second region having the second stretching force can be easily configured in the backsheet.

  ADVANTAGE OF THE INVENTION According to this invention, even if an absorber expand | swells, the absorbent article which made it possible to suppress the fall of the fit with respect to skin can be provided.

The perspective view of the underpants type disposable diaper which materialized the absorptive article of the present invention. The disassembled perspective view of the underpants type disposable diaper which materialized the absorptive article of the present invention. The top view of an absorptive main body. (A) is sectional drawing of an absorptive main body, (b) is sectional drawing which shows the modification which comprised the back seat | sheet by the 3rd sheet | seat element and the 4th sheet | seat element, (c) is one sheet | seat of a back seat | sheet. Sectional drawing which shows the modification comprised with the sheet | seat element. Sectional drawing of the conventional absorptive main body.

With reference to FIG. 1 thru | or FIG. 5, the underpants type disposable diaper in one Embodiment which actualized the absorbent article in this invention is demonstrated.
As shown in FIG. 1, a pants-type disposable diaper 10 (hereinafter simply referred to as “diaper 10”) has a front body 10F having a shape that follows the shape of the wearer's abdomen and a shape that follows the shape of the wearer's back. And a crotch part 10C connecting the front body 10F and the back body 10R.

  In the front body 10F and the back body 10R, the side opposite to the crotch part 10C constitutes a waist part 10W that surrounds a portion around the waist of the wearer, and is provided with a waist opening 10A at the upper end. The left and right ends of the front body 10F, the left and right ends of the back body 10R, and the left and right ends of the crotch 10C are defined as a pair of left and right leg openings 10L having a shape surrounding the thigh portion of the wearer. It is composed. Further, the left and right end portions of the front body 10F and the back body 10R in the trunk periphery direction are joint portions 11.

  FIG. 2 is an exploded perspective view of a pants-type disposable diaper. The front body 10F is composed of a first exterior body 12F, and the back body 10R is composed of a second exterior body 12R. Hereinafter, the first exterior body 12F and the second exterior body 12R are simply referred to as an exterior body 12 collectively.

  The exterior body 12 has a rectangular shape whose longitudinal direction is the direction around the trunk, and is configured by sandwiching an elastic member 15 between sheets 13S and 13B constituting the exterior body 12. As an example, the sheets 13S and 13B constituting the exterior body are nonwoven fabrics made of synthetic fibers made of polyethylene, polypropylene, polyester, and other thermoplastic resins as raw materials, and are liquid-permeable sheets and liquid-impermeable sheets. There may be. The elastic member 15 is an elastic body formed of one or more materials selected from natural rubber, synthetic rubber, urethane, and the like, and is formed in a thread shape, a string shape, a net shape, or a flat shape. A plurality of elastic members 15 are arranged in parallel to each other along the trunk circumference direction.

  The first exterior body 12F and the second exterior body 12R are connected by an absorbent main body 16 constituting the crotch portion 10C. As shown in FIG. 3, the absorptive main body 16 has a rectangular shape whose longitudinal direction is the front-rear direction. The absorbent main body 16 includes a back sheet 17 that is basically impermeable, an absorber 18, and a top sheet 19 having liquid permeability. In the diaper 10, the top sheet 19 is disposed on the inner side in contact with the wearer's skin, the back sheet 17 is disposed on the outer side, and the back sheet 17, the absorber 18, and the top sheet 19 overlap in this order from the outer side. Further, a cover sheet 17A made of a non-woven fabric is disposed on the outside of the back sheet 17 in order to improve the feeling of touch (see FIG. 2). The outer surface of the region overlapping the exterior body 12 in the front-rear direction of the absorbent main body 16 becomes an adherend to be adhered to the sheet 13B on the back side of the exterior body 12.

  The backsheet 17 has a sheet element having air permeability in order to suppress stuffiness between the wearer and the diaper 10 while being liquid-impermeable in order to prevent liquid from leaking to the outer surface of the diaper 10. Is selected. Further, here, a moisture-permeable stretch sheet having moisture permeability and at least stretchability in the front-rear direction is used for the back sheet 17. As an example, the moisture-permeable stretch sheet is a resin composition that is soft and allows moisture to move through the resin while maintaining stretchability regardless of directionality, and facilitates the release of moisture in the resin. Such a moisture-permeable stretch sheet is formed by a roll or a casting method after blending a resin or inorganic fine particles that are incompatible with the polyurethane resin, and by stretching this, a large number of micropores are formed in the film. Can be configured. Alternatively, a film is formed by wet coagulation of a polyurethane resin emulsion, or a foaming agent is blended to form a large number of micropores in the film by foaming. Alternatively, it is formed by an extrusion method. In addition, the back sheet 17 should just be the structure which has a stretching property at least in the front-back direction, the structure which has a stretching property only in the front-back direction other than the structure which has a stretching property regardless of directionality, or the front-back direction and the width direction The structure which has elasticity in these two directions may be sufficient.

Alternatively, the moisture-permeable stretch sheet is a resin composition in which a polyurethane resin is about 65 to 85% by weight, a polyethylene resin is about 30 to 15% by weight, or a compatibilizing agent is 20% by weight or less. And the compounding ratio of a polyurethane resin and a polyethylene resin is selected according to the required softness, stretchability, and moisture permeability. The moisture permeability of the moisture permeable stretch sheet is 2,000 to 15,000 g / m ² 24 hr (JIS Z-208).

  The conventional back sheet 17X (see FIG. 5) is configured by forming a large number of fine holes in order to ensure air permeability with respect to a polyethylene resin film having liquid impermeability. The sheet 17 is different from the conventional back sheet in that it is particularly stretchable.

  The back sheet 17 as described above is longer than the absorber 18 in the front-rear direction, and is also longer than the absorber 18 in the width direction. That is, the back sheet 17 is disposed so as to cover the entire absorber 18 in order to function as a waterproof sheet. The width direction of the back sheet 17 extends to the position of the leg gathers 23.

  The absorber 18 has a band shape so as to straddle the front body 10F, the crotch 10C, and the back body 10R. The material forming the absorber 18 is an absorbent material such as fluff pulp, superabsorbent polymer (SAP), hydrophilic sheet, or the like. For example, the absorbent body 18 is wrapped by a core wrap 18A (see FIG. 4A) made of a hydrophilic sheet, and a tissue 18B (see FIG. 4A) is disposed on the top sheet 19 side. Then, it is disposed and joined between the back sheet 17 and the top sheet 19. The absorbent body 18 expands when it absorbs moisture such as excreta, but the diaper 10 is prevented from being damaged by the backsheet 17 being stretched in accordance with the expansion of the absorbent body 18, so that the fit to the skin is impaired.

  The top sheet 19 is formed of, for example, a woven fabric, a nonwoven fabric, a porous film, or the like. The top sheet 19 is made of, for example, a non-woven fabric having liquid permeability composed of fibers of thermoplastic resin such as polypropylene, polyethylene, polyester, and nylon and subjected to hydrophilic treatment. . Since the cover sheet 17A is the outermost sheet and is a sheet that touches the user, the cover sheet 17A is made of a non-woven fabric or the like that improves the touch feeling.

  On the inner surface of the absorbent main body 16, that is, on the top sheet 19, solid gathers 21 are arranged at both ends along the front-rear direction. Each three-dimensional gather 21 is provided with the 1st elastic member 21E extended in the front-back direction of the absorptive main body 16, and the side sheet | seat 21S which pinches | interposes the 1st elastic member 21E. The first elastic member 21E is arranged with respect to the side sheet 21S in a state where a plurality of the first elastic members 21E are parallel to each other and the hot melt adhesive is applied and stretched, and the side sheet 21S is folded in half. It is sandwiched between the side sheets 21S. The first elastic member 21E is made of the same material as the elastic member 15. The side sheet 21S is composed of a long sheet body that extends in the front-rear direction including, for example, a liquid-impermeable nonwoven fabric.

  The side sheet 21S sandwiching the first elastic member 21E is disposed such that the distal end portion extends from the left and right end portions of the absorbent body 16 toward the center line P direction in the left and right direction, and the base end portion 21B is made of an adhesive. The top sheet 19 or the back sheet 17 is bonded to at least one of the second region 22B and the cover sheet 17A. Further, the side sheet 21S has an edge on the side of the center line P in the width direction at the base end portion 21B as a folded portion 21T so that the folded portion 21T to the distal end portion 21P face both ends in the width direction of the absorbent main body 16. Wrapped. The three-dimensional gather 21 is provided with a fixed region 21A fixed by an adhesive or welding at an end portion in the front-rear direction, and a rising line L1 where the boundary between the fixed region 21A and the non-fixed region rises with respect to the top sheet 19 It becomes. The backsheet 17 extends to the outside in the width direction from the rising line L1.

  Further, the side edge portion of the absorbent main body 16 includes leg gathers 23. In the leg gather 23, the second region 22B extending in the front-rear direction in the width direction of the back sheet 17 functions as an elastic part, and rises due to contraction in the front-rear direction of the elastic part. As shown in FIG. 4A, as an example, the cover sheet 17A does not include a folded portion that is folded in the direction of the center line P in the width direction and extends to the second region 22B. On the other hand, in the conventional diaper, since the back sheet 17X does not have stretchability, the leg gathers 23 are configured by sandwiching the second elastic member 23A between the cover sheets 17A. Therefore, the bent portion 17B of the cover sheet 17A is provided (see FIG. 5). Of course, even if it is a case where it has the 2nd field 22B, it can also be considered as composition provided with a bent part extended to the 2nd field 22B of cover sheet 17A. Thereby, the 2nd area | region 22B is pinched | interposed by the cover sheet | seat 17A, A touch can be improved or the intensity | strength of the leg gather 23 can be raised.

  Here, the relationship among the back sheet 17, the absorber 18, the three-dimensional gather 21, and the leg gather 23 will be described. The width W1 of the back sheet 17 extends to the side edge of the absorbent main body 16, the top sheet 19 and / or the side edge of the cover sheet 17A. In the width direction of the back sheet 17, the area where the absorber 18 exists, specifically, the area including the area where the top sheet 19 overlaps is the first area 22 </ b> A, and the area of the portion protruding from the absorber 18, specifically The area outside in the width direction from the area where the top sheet 19 overlaps is the second area 22B. The second region 22 </ b> B is a region that becomes an elastic part of the leg gather 23.

  The back sheet 17 as a whole has stretchability regardless of directionality. That is, the first region 22A and the second region 22B have a property of expanding and contracting not only in the front-rear direction but also in the width direction. And the 1st field 22A of back seat 17 has the 1st elastic force in the direction of order, and even if absorber 18 absorbs moisture, such as excrement, it expands according to expansion, and a diaper This prevents the 10 fit feeling from being impaired. The second region 22B has a second stretching force in the front-rear direction that is greater than the first stretching force in the front-rear direction of the first region 22A.

  More specifically, the backsheet 17 can be composed of a first sheet element 24A constituting one first region 22A and a second sheet element 24B constituting two second regions 22B. In this case, the first sheet element 24A is a moisture-permeable stretch sheet having the same size and shape as the first region 22A and having a first stretch force. Each second sheet element 24B is a moisture-permeable stretch sheet having the same size and shape as the second region 22B and having a second stretch force. For each side edge portion extending in the front-rear direction of the first sheet element 24A, one side edge portion extending in the front-rear direction of the second sheet element 24B is overlapped and joined by an adhesive or welding (FIG. 4A). )reference). The first sheet element 24A and the second sheet element 24B may be the same material or different materials. In the backsheet 17 configured as described above, the stretching force in the front-rear direction is greater in the second region 22B than in the first region 22A, and the first region 22A is a low elastic stretch region, and the second region 22B is a highly elastic stretchable region.

  For example, it is preferable that the second stretch force in the front-rear direction of the second region 22B is twice or more higher than the first stretch force in the front-rear direction of the first region 22A. Here, for example, when the first sheet element 24A and the second sheet element 24B are made of the same material, the second stretch force of the second region 22B is the first sheet element 24A of the first stretch force constituting the first region 22A. It can be realized by extending the length to 2 to 3 times and joining the extended second sheet element 24B to the first sheet element 24A.

  This is because if the second stretch force is smaller than twice the first stretch force, the leg gathers 23 cannot stand up firmly. Moreover, it is preferable that the 2nd expansion-contraction force in the front-back direction of 2nd area | region 22B is 3 times or less with respect to the 1st expansion-contraction force in the front-back direction of 1st area | region 22A. This is because when the second stretch force is greater than three times the first stretch force, the leg gathers 23 are rounded and the function of the leg gathers 23 is reduced. As described above, the second region 22B functions as an elastic member of the leg gather 23 by making the second stretch force in the front-rear direction of the second region 22B triple the first stretch force in the front-rear direction of the first region 22A. Thus, the leg gathers 23 can be firmly raised.

  In the backsheet 17, the boundary between the first region 22 </ b> A and the second region 22 </ b> B in the width direction is the position of the rising line L <b> 1 where the solid gather 21 rises. As a result, the gathers around the legs have a double structure of the three-dimensional gather 21 and the leg gathers 23, and leakage from the legs can be suppressed.

As mentioned above, according to the said embodiment, the effect enumerated below can be acquired.
(1) In the absorptive main body 16, since the moisture-permeable elastic sheet is used for the back sheet 17, even if the absorber 18 expands, the back sheet 17 expands accordingly. Therefore, the diaper 10 can suppress a decrease in fit to the skin even after the absorbent body 18 has expanded.

(2) The moisture permeability of the back sheet 17 is 2,000 to 15,000 g / m ² 24 hr (JIS Z-208). Thereby, the stuffiness etc. between a wearer and the diaper 10 can be suppressed.

  (3) The back sheet 17 uses a moisture-permeable stretch sheet, and includes a first region 22A having a first stretch force in the front-rear direction and a second region 22B having a second stretch force in the front-rear direction, and the second region 22B. The leg gather 23 is started up. Conventionally, as shown in FIG. 5, the second elastic member 23 </ b> A is used for the leg gather, but the second elastic member 23 </ b> A can be replaced with the second region 22 </ b> B of the backsheet 17. Therefore, the diaper 10 can realize a reduction in the number of parts, and can further improve production efficiency.

  (4) In addition, the back sheet 17 includes the first region 22A composed of the first sheet element 24A, and the second region 22B composed of the second sheet element 24B, so that the expansion / contraction force of each region can be expanded or contracted as desired. Can be easily set to force.

  (5) The second stretch force in the front-rear direction of the second region 22B is two to three times the stretch force in the front-rear direction of the first region 22A. This second stretching force is approximately the same as the stretching force of the second elastic member 23 </ b> A that has been used in the leg gathers 23 in the past. Thereby, the leg gathers 23 can be raised firmly.

  (6) The leg gather 23 is not required to have a configuration in which the cover sheet 17A is folded and the second elastic member 23A is sandwiched and fixed. Therefore, also in this respect, the diaper 10 can improve production efficiency.

In addition, the said embodiment can also be suitably changed and implemented as follows.
The back sheet 17 is composed of one third sheet element 24C having a size combining the first region 22A and the second region 22B, and one fourth sheet element 24D having a size corresponding to the first region 22A. It can also consist of. In this case, the third sheet element 24C is a moisture-permeable stretch sheet having a second stretch force. The fourth sheet element 24D is a moisture-permeable stretch sheet having a first stretch force. The fourth sheet element 24D is overlapped with a portion corresponding to the first region 22A of the third sheet element 24C and joined by an adhesive or welding (see FIG. 4B). The third sheet element 24C and the fourth sheet element 24D may be the same material or different materials. According to such a back sheet 17, it can be constituted by only two sheet elements 24C and 24D.

  The backsheet 17 can also be configured by a single sheet element 24E having a size that combines the first region 22A and the second region 22B. The sheet element 24E is composed of a moisture-permeable stretch sheet (see FIG. 4C). In this case, it is configured such that the front and rear direction expands and contracts from the first region 22A by scratching the second region 22B in the width direction by processing such as gear stretching with respect to the moisture-permeable stretch sheet having the first stretch force as a whole. can do. Such a backsheet is composed of one sheet element 24E, and the configuration can be simplified.

The moisture permeability of the back sheet 17 is not limited to 2,000 to 15,000 g / m ² 24 hr (JIS Z-208). For example, if moisture between the diaper 10 and the wearer is discharged by other means, the moisture permeability of the back sheet 17 may be smaller than 2,000 g / m ² 24 hr. Further, when the function of discharging moisture between the diaper 10 and the wearer by other means is poor, the moisture permeability of the back sheet 17 may be larger than 15,000 g / m ² 24 hr.

  In the moisture-permeable stretch sheet of the back sheet 17, the second stretch force in the front-rear direction of the second region 22B only needs to be greater than the first stretch force in the front-rear direction of the first region 22A, and the front-rear direction of the first region 22A It may not be 2 to 3 times the first stretching force at. For example, the leg gathers 23 may be configured to add a second elastic member 23A in addition to the second region 22B. That is, the elasticity in the front-rear direction of the second region 22B may be for assisting the second elastic member 23A. Further, the elasticity of the second region 22B in the front-rear direction may be such that it is assisted by the second elastic member 23A. When the second elastic member 23A is required, a bent portion 17B that sandwiches and fixes the second elastic member 23A is required.

-As the diaper 10, it is good also as a structure only of the leg gathers 23, without providing the three-dimensional gathers 21. FIG.
In the diaper 10, the moisture-permeable stretch sheet as the back sheet 17 is a size that covers at least the entire absorbent body 18 so that the absorbent body 18 expands in accordance with the expansion of the absorbent body 18 when the absorbent body 18 expands. I just need it.

  -The disposable diaper may be a tape-type diaper. Moreover, the disposable diaper for adults, such as an elderly person and a disabled person for infants or those who require nursing care, may be used. Furthermore, the absorbent article may be a urine pad, a light incontinence pad, a sanitary napkin, or the like.

P ... center line, L1 ... rising line, W1 ... length, 10A ... waist circumference, 10C ... crotch, 10F ... front body, 10L ... leg circumference opening, 10R ... back body, 10W ... waist circumference, DESCRIPTION OF SYMBOLS 11 ... Joint part, 12 ... Exterior body, 12F ... 1st exterior body, 12R ... 2nd exterior body, 13B ... Sheet, 13S ... Sheet, 15 ... Elastic member, 16 ... Absorbent main body, 17 ... Back sheet, 17A ... Cover sheet, 17B ... bent portion, 17X ... backsheet, 18 ... absorber, 18A ... core wrap, 18B ... tissue, 19 ... topsheet, 21 ... solid gather, 21A ... fixed region, 21B ... proximal end, 21E ... 1st elastic member, 21P ... tip part, 21S ... side sheet, 21T ... folding part, 22A ... 1st field, 22B ... 2nd field, 23 ... leg gather, 23A ... 2nd elastic member, 24A ... 1st sea Elements, 24B ... second sheet element, 24C ... third sheet element, 24D ... fourth sheet element, 24E ... sheet element.

Claims (7)

A back sheet composed of a moisture-permeable stretch sheet that stretches at least in the front-rear direction of the absorbent article;
A liquid-permeable top sheet located closer to the wearer's skin than the back sheet;
An absorbent article comprising: an absorbent body positioned between the top sheet and the back sheet. The absorbent article according to claim 1, wherein the moisture permeability of the back sheet is 2,000 to 15,000 g / m ² 24 hr (JIS Z-208). The backsheet includes a first region where the absorber exists in a width direction intersecting the front-rear direction, and a second region at a position protruding from the absorber on both sides of the first region,
The absorbent article according to claim 1 or 2, wherein a second stretch force in the front-rear direction of the second region is greater than a first stretch force in the front-rear direction of the first region. The absorbent article according to claim 3, wherein the second stretch force in the front-rear direction of the second region is two to three times the first stretch force in the front-rear direction of the first region. A cover sheet that is located on the opposite side of the skin side with respect to the back sheet and that overlaps the first region and the second region;
5. The cover sheet according to claim 3, wherein the cover sheet does not include a folded portion that is folded in the direction of the center line in the width direction and extends to the second region in the width direction intersecting the front-rear direction. Absorbent article. A front body that covers the abdomen of the wearer and a back body that covers the back of the wearer;
The back sheet, the top sheet, and the absorber are absorbent main bodies that constitute a crotch portion between the front body and the back body,
The absorbent article according to any one of claims 3 to 5, wherein the second region constitutes a leg gather. The first region and the second region are separate sheet elements;
The absorptive article according to claim 3. The back sheet is constituted by joining the 1st sheet element which constitutes the 1st field, and the 2nd sheet element which constitutes the 2nd field.

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