Patent Description:
In absorbent articles, elastic characteristics are typically imparted to leg portions, waist portions, and the like to improve fitness to the surfaces of bodies. A typical approach to impart elastic characteristics is fixing of elongated elastically stretchable members, such as rubber threads, in a state stretched in the longitudinal direction. In order to impart elasticity over a certain range of width, rubber threads are disposed and fixed in the width direction at intervals in some embodiments. In addition, an approach to impart excellent surface fitting is fixing of elastic film in a state stretched in a direction of imparting elasticity (for example, see Patent Literature <NUM>).

According to a stretchable structure using the elastic film (hereinafter also referred to as an elastic film stretchable structure), a stretchable region is composed of a first sheet layer, a second sheet layer, and an elastic film interposed therebetween, and the first sheet layer and the second sheet layer are joined via through holes formed in the elastic film at a large number of dot-like sheet bond portions arranged at intervals in a stretching and contracting direction and a direction orthogonal thereto while the elastic film is stretched in the stretching and contracting direction along the surfaces of the first sheet layer and the second sheet layer. In such an elastic film stretchable structure, in a natural length state, as the elastic film contracts between sheet bond portions, an interval between sheet bond portions is decreased, and a contraction wrinkle extending in the direction orthogonal to the stretching and contracting direction is formed between the sheet bond portions in the first sheet layer and the second sheet layer. On the contrary, in a stretched state, as the elastic film is stretched between the sheet bond portions, the interval between the sheet bond portions is increased and the contraction wrinkle in the first sheet layer and the second sheet layer is extended, and elastic stretching is allowed so that the first sheet layer and the second sheet layer can be completely spread. This elastic film stretchable structure has advantages as follows: surface fitness is excellent; the first sheet layer and the second sheet layer are not joined to the elastic film and joined each other but at an extremely low level, thus the elastic film stretchable structure has a satisfactory flexibility; and the through holes of the elastic film contribute to improvement in air permeability.

However, in a method described in Patent Literature <NUM>, through holes of an elastic film are formed by extrusion, and a first sheet layer and a second sheet layer are directly joined by welding at positions of the through holes. Thus, there is a concern that since the peeling strength is low, peeling may occur when a strong force is applied. In addition, in Patent Literature <NUM>, since the through holes of the elastic film are formed by the extrusion, an elastic film <NUM> is not left between a first sheet layer 20Aanda second sheet layer 20B as illustrated in <FIG>, and there is a concern that extrusion debris (not illustrated) may be movably left around the through holes <NUM>.

In addition, as illustrated in <FIG>, it can be assumed that the first sheet layer 20A and the second sheet layer 20B are joined through the elastic film <NUM> without forming the through holes in the elastic film <NUM>. However, in this case, there is a problem that not only peeling strength is low, but also air permeability is extremely low due to the absence of the through holes.

Meanwhile, in the above-mentioned conventional elastic film stretchable structure, air permeability can hardly be expected where the through holes are not provided. Therefore, improvement of air permeability in the through holes is significantly important in improving whole air permeability. In an absorbent article, a decrease in air permeability causes discomfort due to stuffiness.

Regarding this point, as another embodiment, Patent Literature <NUM> proposes that the sheet bond portions be fractured to form vent holes by pulling the sheet bond portions in the direction orthogonal to the stretching and contracting direction after forming the sheet bond portionsby welding. However, since an edge of a fractured portion corresponds to a sharp texture, the proposal may not be preferable for an absorbent article to be worn on a body by hand.

Patent Literature <NUM> discloses a method of making a breathable, elastic film laminate.

Patent Literature <NUM> discloses an underpants-type disposable diaper in which an outer body is formed by stacking an elastic sheet layer between a first sheet layer (20A) and a second sheet layer.

Patent Literature <NUM> discloses a method of forming an elastic comprising at least one elastic film and least two nonwoven webs laminated to each of the sides of the elastic film.

Patent Literature <NUM> discloses an elastic laminate material comprising at least one elastic film layer and at least one nonwoven layer.

Patent Literature <NUM> discloses an absorbent garment comprising an absorbent member and a laminate.

In this regard, a first problem is to achieve both high air permeability and high peeling strength.

In addition, a second problem is to improve air permeability without impairing a texture in an elastic film stretchable structure.

The invention solving the above first problem is described below.

In the stretchable region of the invention, when the elastic film is in the natural length state, the first sheet layer and the second sheet layer between the sheet bond portions stretch in a direction away from each other, and thus a contraction wrinkle extending in a direction intersecting the stretching and contracting direction is formed. When a gap is formed between the through holes of the elastic film and the sheet bond portions in this state, air permeability is imparted due to the gap even when a material of the elastic film is a non-porous film or a sheet. Further, even when any gap is not formed between the through holes of the elastic film and the sheet bond portions in this state, since the through holes of the elastic film stretch while the sheet bond portions do not stretch in a worn state of being stretched to some extent in a width direction, a gap is formed between the through holes of the sheet bond portions in the elastic film and the sheet bond portions. Thus, air permeability is imparted due to the gap even when a material of the elastic film is a non-porous film or a sheet. Therefore, the stretchable region of the invention has high air permeability. In addition, since the first sheet layer and the second sheet layer are joined at least by the melted and solidified material of the elastic film among the first sheet layer and the second sheet layer in the sheet bond portions, peeling strength is high as understood from Example described below. Therefore, according to the invention, it is possible to achieve both high air permeability and high peeling strength. When such a structure is adopted, improved adhering of the melted and solidified material of the elastic film to the first sheet layer and the second sheet layer is obtained, and, in addition, strength of the first sheet layer and the second sheet layer rarely decreases. Thus, peeling strength is further enhanced.

The absorbent article according to claim <NUM>, wherein
a part of the first sheet layer and the second sheet layer is not melted at the sheet bond portions.

The absorbent article according to claim <NUM> or <NUM>, wherein.

The area of each of the sheet bond portions, the area of the opening of each of the through holes, and the area rate of the sheet bond portions may be appropriately determined. In general, it is desirable to set the areas and the area rate within the above ranges.

The absorbent article according to any one of claims <NUM> to <NUM>, wherein the absorbent article is an underpants-type disposable diaper having.

The outer body of the underpants-type disposable diaper having such a structure is required to have elasticity in a wide range and be excellent in air permeability, and thus is particularly suitable for the invention.

A method of manufacturing an absorbent article according to claim <NUM> including a stretchable region stretchable at least in one direction, wherein.

When welding is performed by heat sealing, ultrasonic sealing, etc. in an arrangement pattern of the sheet bondportions in a state in which the elastic film is interposed between the first sheet layer and the second sheet layer as described above, the through holes may be formed in the elastic film, as well as the first sheet layer and the second sheet layer may be joined by solidification of the melted material of the elastic film via the through holes, and thus manufacture may be simply and efficiently performed. Furthermore, both high air permeability and high peeling strength are achieved in the manufactured stretchable region similarly to that described in claim <NUM>.

The method of manufacturing an absorbent article according to claim <NUM>, wherein a melting point of the first sheet layer and a melting point of the second sheet layer are higher than a melting point of the elastic film, the elastic film is melted at the positions for welding, and a part of the first sheet layer and the second sheet layer is not melted or a whole of the first sheet layer and the second sheet layer is not melted.

It is possible to manufacture the stretchable region of the invention described in claim <NUM> while having the same advantage as that in the invention described in claim <NUM>.

The invention solving the above second problem is described below.

An absorbent article, which is not according to the invention, having an absorber that absorbs excrement, the absorbent article comprising.

In the disclosure, air permeability in the thickness direction may be improved by the through holes of the elastic film and the vent hole of at least one of the first sheet layer and the second sheet layer. Furthermore, since a vent hole is formed by piercing at least one of the first sheet layer and the second sheet layer at a portion other than the sheet bond portions, a texture is not impaired unlike a case in which the vent hole is formed by fracture of the sheet bond portions as in Patent Literature <NUM>. Here, the vent hole of the disclosure is formed by piercing, and thus passages, which are originally possessed by the material for air permeability, are not included. For example, in a case that the material of the first sheet layer and of the second sheet layer are composed of air permeable fiber materials such as nonwoven fabrics, intervals between fibers are not included in the above "vent hole" of the disclosure.

The absorbent article according to item <NUM>, which is not according to the invention, wherein in a state in which the stretchable region is stretched, the vent hole is disposed with respect to the through holes such that a part or a whole of the vent hole overlaps each of the through holes.

Since the through hole formed in the elastic film is enlarged when the stretchable region is stretched at the time of use, air permeability via the through hole is particularly improved when the vent hole is disposed such that a part or a whole of the vent hole overlaps the enlarged through hole, which is preferable.

The absorbent article according to item <NUM>, which is not according to the invention, wherein independently of a state in which the stretchable region is stretched or not, none of the vent hole overlaps the through holes.

When the stretchable region is stretched during use, the through holes formed in the elastic film are enlarged. Thus, when a part or a whole of the vent hole is disposed to overlap the enlarged through hole, there is a concern that a skin exposure may increase due to improvement of permeability, or leak prevention may deteriorate even though air permeability is improved. Therefore, a configuration described in this item is also one of preferable modes, which is not according to the invention.

The absorbent article according to any one of items <NUM> to <NUM>, which is not according to the invention, wherein the first sheet layer is a nonwoven fabric and the second sheet layer is a nonwoven fabric, and the number of vent holes per unit area is smaller than the number of through holes per unit area.

The first sheet layer and the second sheet layer are layers that cover the elastic film, and are members that require durability such as rub resistance. In addition, when the first sheet layer is composed of a nonwoven fabric and the second sheet layer is composed of a nonwoven fabric, the number of vent holes may not be excessively increased since the material has air permeability. On the other hand, a considerable number of through holes of the elastic film are used to ensure air permeability and join uniformly the first sheet layer and the second sheet layer as one unit. Therefore, in a preferable mode, which is not according to the invention, the number of vent holes is set to be smaller than the number of through holes.

The absorbent article according to any one of items <NUM> to <NUM>, which is not according to the invention, wherein at least one vent hole is formed on each side of each of the sheet bond portions in the stretching and contracting direction.

When the stretchable region is stretched during use, the through holes formed in the elastic film are enlarged at both sides of the sheet bond portions in the stretching and contracting direction. Thus, it is preferable to form the vent hole at the position described in this item in terms of improvement in air permeability compared with cases in which it is not.

The absorbent article according to any one of items <NUM> to <NUM>, which is not according to the invention, wherein an area of the vent hole is in a range of <NUM> to <NUM><NUM>, and an area rate of the vent hole is in a range of <NUM> to <NUM>%.

The area of the vent hole is not particularly restricted. However, when the area is excessively small or an excessively small number of vent holes are present, an effect of improving air permeability becomes poor. When the size is excessively large or an excessively large number of vent holes are present, a decrease in strength or deterioration in appearance of the sheet layers is caused. Thus, the size is preferable set within the range described in this item, which is not according to the invention.

The absorbent article according to any one of items <NUM> to <NUM>, which is not according to the invention, wherein.

The area of the vent hole is not particularly restricted. However, when the area is excessively small or an excessively small number of vent holes are present, an effect of improving air permeability becomes poor. When the size is excessively large or an excessively large number of vent holes are present, a decrease in strength or deterioration in appearance of the sheet layers is caused. Thus, it is preferable to set the size within the range described in this item, which is not according to the invention.

The elastic film stretchable structure of the disclosure is excellent in air permeability, and thus is particularly suitable for the outer body of the underpants-type disposable diaper.

As described above, according to the invention that solves the first problem, there is an advantage that both high air permeability and high peeling strength may be achieved, etc. In addition, according to the disclosure that solves the second problem, which is not according to the invention, there is an advantage that air permeability may be improved without impairing a texture in an elastic film stretchable structure, etc..

Hereinafter, an embodiment of the invention will be described with reference to accompanying drawings. A dotted portion in a cross-sectional view indicates joining means such as a hot-melt adhesive.

<FIG> illustrate an underpants-type disposable diaper. This underpants-type disposable diaper (hereinafter also simply referred to as a diaper) has an outer body <NUM> that includes a front body F and a back body B as one unit, an inner body <NUM> that is fixed to the internal surface of the outer body <NUM> as one unit. Further, in the inner body <NUM>, an absorber <NUM> is interposed between a liquid pervious top sheet <NUM> and a liquid impervious sheet <NUM>. In manufacturing, after a back surface of the inner body <NUM> is joined to the internal surface (upper surface) of the outer body <NUM> using j oiningmeans such as a hot-melt adhesive, the inner body <NUM> and the outer body <NUM> are folded at a center in a front-back direction (vertical direction) corresponding to a boundary between the front body F and the back body B, and both side portions thereof are joined to each other by heat sealing, a hot-melt adhesive, etc. to form a side seal portion <NUM>, thereby obtaining an underpants-type disposable diaper in which a waist opening and a pair of right and left leg openings are formed.

With reference to <FIG>, the inner body <NUM> includes a top sheet <NUM> composed of, for example, non-woven fabric, a liquid-impermeable sheet <NUM> composed of, for example, polyethylene, and an absorber <NUM> between the top sheet <NUM> and the liquid-impermeable sheet <NUM>. The inner body <NUM> is configured to absorb and retain excretory fluid passing through the top sheet <NUM>. The inner body <NUM> may have any planar shape and typically has a substantially rectangular shape as shown in the drawing.

The top sheet <NUM> that covers a front surface side (to come into contact with the skin) of the absorber <NUM> is preferably composed of perforated or imperforate nonwoven fabric or a porous plastic sheet. Examples of the raw fibers of the nonwoven fabric include synthetic fibers, such as olefin fibers, e.g., polyethylene and polypropylene, polyester fibers, and polyamide fibers; recycled fibers, such as rayon and cupra; and natural fibers, such as cotton. The nonwoven fabric can be produced by any process, for example, spun lacing, spun bonding, thermal bonding, melt blowing, or needle punching. Among these processes, preferred are spun lacing in view of flexibility and drape characteristics and thermal bonding in view of bulky soft products. A large number of through holes formed in the liquid-pervious front surface sheet <NUM> facilitates absorption of urine and achieves dry touch characteristics. The top sheet <NUM> extends around the side edges of the absorber <NUM> and extends to the back surface side of the absorber <NUM>.

The liquid-impermeable sheet <NUM>, covering the back surface side (not in contact with skin) of the absorber <NUM> is composed of a liquid-impervious plastic sheet, for example, polyethylene sheet or polypropylene sheet. Recently, permeable films have been preferably used in view of preventing stuffiness. This water-block permeable sheet is a micro-porous sheet prepared through melt-kneading an olefin resin, for example, polyethylene resin or polypropylene resin, and inorganic filler, forming a sheet with the kneaded materials, and then uniaxially or biaxially elongating the sheet.

The absorber <NUM> may be composed of a well-known basic component, such as an accumulated body of pulp fibers, an assembly of filaments, composed of, for example, cellulose acetate, or nonwoven fabric, and the absorber <NUM> may include as necessary high-absorbent polymer mixed or fixed to the basic component. The absorber <NUM> may be wrapped with a liquid-permeable and liquid-retainable package sheet <NUM>, such as a crepe sheet, to retain the shape and polymers, as required.

The absorber <NUM> has a substantially hourglass shape having a narrow portion 13N with a width narrower than those of the front and back end portions of the absorber <NUM>, at a crotch portion. Alternatively, the absorber <NUM> may have any other shape, for example, a rectangular shape, as appropriate. The size of the narrow portion 13N may be appropriately determined. The narrow portion 13N may have a length of approximately <NUM> to <NUM>% of the entire length of the diaper along the front-back direction, and a width, at the narrowest region, of approximately <NUM> to <NUM>% of the entire width of the absorber <NUM>. If the inner body <NUM> has a substantially rectangular planar shape in the case of the absorber with such a narrower part 13N, the inner body <NUM> has portions free of the absorber <NUM> according to the narrower part 13N of the absorber <NUM>.

Three-dimensional gathers BS, which are configured to fit around the legs, are formed on both side portions of the inner body <NUM>. With reference to <FIG> and <FIG>, the three-dimensional gathers BS are each composed of a gather nonwoven fabric <NUM> folded into a duplicate sheet consisting of a fixed section fixed to the side portion of the back surface of the inner body, a main section extending from the fixed section around a side portion of the inner body to the side portion of the front surface of the inner body, lying down sections formed by fixing the front end portion and back end portion of the main section in a lying down state to the side portion of the front surface of the inner body, and a free section formed in an un-fixed state between the lying down sections.

Elongated gather elastic members <NUM> are disposed in the tip portion of the free sections of the duplicate sheet. As illustrated by the chain double-dashed line in <FIG>, part of the nonwoven fabric protruding from a side edge of the absorber is erected by elastic stretching force of the gather elastic members <NUM> to form a three-dimensional gather BS in a completed product.

The liquid impervious sheet <NUM> is folded back to the back surface side together with the top sheet <NUM> at both sides of the absorber <NUM> in the width direction. The liquid-impervious back surface sheet <NUM> is preferably opaque to block transmission of brown color of stool and urine. Preferred examples of the opacifying agent compounded in the plastic film include colorant or filler, such as calcium carbonate, titanium oxide, zinc oxide, white carbon, clay, talc, and barium sulfate.

The gather elastic member <NUM> may be composed of commodity materials, for example, styrene rubber, olefin rubber, urethane rubber, ester rubber, polyurethanes, polyethylene, polystyrene, styrene-butadiene, silicones, and polyester. The gather elastic members <NUM> preferably have a fineness of <NUM> dtex or less and are disposed under a tension of <NUM>% to <NUM>% at an interval of <NUM> or less to be hidden from outside view. The gather elastic member <NUM> may have a string shape shown in the drawing or a tape shape with an appropriate width.

Like the top sheet <NUM>, the gather nonwoven fabric <NUM> may be composed of raw fibers including synthetic fibers, such as olefin fibers of, for example, polyethylene fibers or polypropylene fibers; polyester fibers and amide fibers; recycled fibers of, for example, rayon and cupra; and natural fibers such as cotton. The gather nonwoven fabric may be prepared by any appropriate process, for example, spun bonding, thermal bonding, melt blowing, or needle punching. In particular, the basis weight should be reduced for production of a nonwoven fabric that can prevent stuffiness and has high air permeability. The gather nonwoven fabric <NUM> is preferably a water-repellent nonwoven fabric coated with a water repellent agent, for example, a silicone-based agent, a paraffin-metallic agent, or an alkyl chromic chloride agent to decrease permeability of urine and the like, to prevent diaper rash, and to enhance feeling to skin (dryness).

As illustrated in <FIG>, the back surface of the inner body <NUM> is fixed to the internal surface of the outer body <NUM> by, for example, a hot-melt adhesive in an internal and external fixed region 10B (shaded area). The internal and external fixed region 10B extends over with a width range corresponding to a range from a side portion <NUM> free of the absorber at one side to another side portion <NUM> free of the absorber at the other side at the both front and back sides of the side portions <NUM>. Side edges of the internal and external fixed region 10B are preferably positioned at lateral sides of the middle of the side portions <NUM> free of the absorber in the width direction. In particular, the internal and external fixed region 10B is preferably fixed to the substantially whole inner body <NUM> in the width direction and fixed to the substantially whole outer body <NUM> in the front-back direction.

With reference to <FIG> and <FIG>, front and back cover sheets <NUM>, <NUM> may be provided to cover the front and back end portions of the inner body <NUM> attached to the internal surface of the outer body <NUM> to prevent leakage from the front and rear edges of the inner body <NUM>. In more detail, the front cover sheet <NUM> extends over the entire width of the front body F on the internal surface of the front body F from the internal surface of the folded part 20C at the waist-side end of the front body F to a position overlapping with the front end portion of the inner body <NUM>. The back cover sheet <NUM> extends on the internal surface of the back body Ba over the entire width, and extends over the entire width of the back body B from the internal surface of the folded part 20C at the waist-side end of the back body B to a position overlapping with the back end portion of the inner body <NUM>, in the embodiment illustrated in the drawings. Minor non-bonded regions are provided over the entire width (or only at the central portion) at side edge portions of the front and back cover sheets <NUM> and <NUM> at the crotch portion-side. The front and back cover sheets <NUM> and <NUM> having such non-bonded regions can prevent leakage of the adhesive and function as barriers against leakage when slightly suspended from the top sheet.

As shown in the embodiment illustrated in the drawings, the front and back cover sheets <NUM>, <NUM> as separate components advantageously enlarge the range of choice of material, but disadvantageously needs additional materials and manufacturing processes. Thus, the folded part 20C formed by folding back the outer body <NUM> toward the inner surface side of the diaper are respectively extended to portions overlapping with the inner body <NUM>, so as to have the same function as that of the cover sheets <NUM>, <NUM>.

First, a mode for solving the first problem will be described with reference to <FIG>. In the outer body <NUM>, as illustrated in <FIG>, the elastic film <NUM> and elongated elastic members <NUM> along the width direction are arranged between the first sheet layer 20A and the second sheet layer 20B, and elasticity in the width direction is imparted. A planar shape of the outer body <NUM> corresponds to a pseudo-hourglass shape as a whole due to a concave line around leg <NUM> formed to form a leg opening at each of intermediate both side portions. The outer body <NUM> may be divided into two front and back parts, and the both parts may be separated from each other in the front-back direction by the crotch portion.

More specifically, in the outer body <NUM> of the illustrated mode, the waist portion elastic members <NUM> are provided in the waist end portion region in the torso region T defined as a vertical direction range of the side seal portion <NUM> in which the front body F and the back body B are joined. The waist portion elastic members <NUM> of the illustrated mode correspond to elongated elastic members such as a plurality of rubber threads disposed at intervals in the vertical direction, and apply a stretching force to tighten around the waist of the body. The waist portion elastic members <NUM> are not disposed closely substantially in a bundle, and three or more, preferably five or more members are disposed at intervals of about <NUM> to <NUM> to form a predetermined stretchable zone. A stretch rate of the waist portion elastic member <NUM> in fixing may be appropriately determined. However, the stretch rate may be set to about <NUM> to <NUM>% in the case of normal adult use. One or a plurality of belt shaped elastic members may be used as the waist portion elastic member <NUM>.

The rubber thread is used as the waist portion elastic member <NUM> in an illustrated example. However, for example, a tape shaped elastic member may be used, and an elastic film described below may be extended to the waist end portion region instead of using the tape shaped elastic member. The waist portion elastic member <NUM> in the illustrated mode is interposed in the folded part 20C formed by folding back a component of the second sheet layer 20B to the internal surface side at a waist opening edge. However, the waist portion elastic member <NUM> may be interposed between a component of the first sheet layer 20A and the component of the second sheet layer 20B.

The first sheet layer 20A and the second sheet layer 20B may be composed of any sheet members, preferably nonwoven fabrics in view of air permeability and flexibility. The nonwoven fabric may be composed of any raw fiber. Examples of the raw fiber include synthetic fibers, such as olefin fibers, e.g., polyethylene fibers and polypropylene fibers, polyester fibers, and polyamide fibers; recycled fibers, such as rayon and cupra; natural fibers, such as cotton; and blend or conjugate fibers composed of two or more of these fibers. The nonwoven fabric may be prepared by any process. Examples of such a process include well-known processes, such as spun lacing, spun bonding, thermal bonding, melt blowing, needle punching, air-through processes, and point bonding. The nonwoven fabric preferably has a basis weight of approximately <NUM> to approximately <NUM>/m<NUM>. The first sheet layer 20A and the second sheet layer 20B may be composed of a pair of facing layers prepared by folding back a single sheet that is partially or entirely folded back.

In this embodiment, as shown in <FIG>, the elastic film stretchable structures 20X are formed in the torso region T of the front body F, the torso region T of the back body B, and an intermediate region L therebetween in the outer body <NUM>. That is, in the stretchable structures 20X of the outer body <NUM>, the non-stretchable region <NUM> is formed in the intermediate portion in the width direction, which includes parts of the outer body <NUM> overlapping with the absorber <NUM> (the non-stretchable region <NUM> may entirely or partly overlap with the absorber <NUM> and preferably should contain the substantially entire fixed portion 10B of the inner body) as well as the stretchable regions <NUM> extend to the side seal portions <NUM> in the width direction. The elastic film <NUM> is, as shown in <FIG>, stacked between the first sheet layer 20A and the second sheet layer 20B over the entire stretchable regions <NUM> and the non-stretchable region <NUM>, and the first sheet layer 20A and second sheet layer 20B are joined at a large number of sheet bond portions <NUM> arrayed in the stretching and contracting direction and the perpendicular direction thereto at predetermined intervals via the through holes <NUM> formed in the elastic film <NUM> while the elastic film <NUM> is being stretched in the width direction. In this case, it is desirable that the first sheet layer 20A is not and the second sheet layer 20B is not joined to the elastic film <NUM> (except for a melted and solidified material describedbelow). However, joining is allowed.

Basically, as the area rate of the sheet bond portions <NUM> increases in the elastic film stretchable structure 20X, portions contracted by the elastic film <NUM>, of the first sheet layer 20A and the second sheet layer 20B decrease, and the elongation at the elastic limit is likely to decrease. Accordingly, the area rate of the openings of the through holes <NUM> in the elastic film <NUM> increases, and thus the proportion of the elastic film <NUM> continuing in the stretching and contracting direction decreases in a direction orthogonal to the stretching and contracting direction. Accordingly, the contraction force to be generated in stretching decreases, and the risk of rupture of the elastic film <NUM> increases. In view of such characteristics, the area rate of the sheet bond portions <NUM> in the non-stretchable region <NUM> is determined to be larger than that in the stretchable regions <NUM>, such that the elongation at the elastic limit in the stretching and contracting direction is <NUM>% or less (preferably <NUM>% or less, more preferably <NUM>%). In contrast, the area rate of the sheet bond portions <NUM> in the stretchable regions <NUM> is determined to be smaller than that in the non-stretchable region <NUM>, such that the elongation at the elastic limit in the stretching and contracting direction is <NUM>% or higher (preferably <NUM> to <NUM>%).

In the stretchable region <NUM>, as illustrated in <FIG>, when the elastic film <NUM> is in the natural length state, the first sheet layer 20A and the second sheet layer 20B between the sheet bond portions stretch in a direction away from each other, and thus a contraction wrinkles <NUM> extending in a direction intersecting the stretching and contracting direction is formed. In a worn state in which the elastic film <NUM> is stretched to an extent in the width direction, as illustrated in <FIG>, the contraction wrinkles <NUM> are still remain although the contraction wrinkles <NUM> are stretched. In addition, as in the illustrated mode, in a case that the first sheet layer 20A is not and the second sheet layer 20B is not joined to the elastic film <NUM> in a portion other than between the first sheet layer 20A and the second sheet layer 20B in the sheet bond portions <NUM> in the non-stretchable region <NUM>, as understood from <FIG> assuming the worn state and <FIG> assuming a completely spread state of the first sheet layer 20A and the second sheet layer 20B, a gap is formed between the through hole <NUM> of each of the sheet bond portions in the elastic film <NUM> and each of the sheet bond portions <NUM> in these states, and thus air permeability is imparted due to the gap even when a material of the elastic film <NUM> is a non-porous film or a non-porous sheet. States of the contraction wrinkles <NUM> in the worn state and the natural length state are shown in sample photographs of <FIG>.

In the non-stretchable region <NUM>, as understood from the sample photographs of <FIG>, a raised portion or an extremely fine wrinkle is formed between the sheet bond portions <NUM>. However, since the area rate of the sheet bond portions <NUM> is significantly high, elasticity is substantially eliminated.

With reference to <FIG> and <FIG>, ends of the stretchable regions <NUM> adjacent to the non-stretchable regions <NUM> are set to buffer stretchable sections <NUM> each having a smaller area rate of the sheet bond portions <NUM> than that of the remaining sections or main stretchable sections <NUM> of the stretchable regions <NUM>. When stretched, the buffer stretchable sections <NUM> are assumed to cause the following variations: In the case where the buffer stretchable sections <NUM> and the main stretchable sections <NUM> are stretched from the natural length state by gradually increasing stress, there are the first phase and the second phase. In the first phase, while both of the buffer stretchable sections <NUM> and the main stretchable sections <NUM> are stretched, the buffer stretchable sections <NUM> are stretched to the elastic limit into a completely spread state (illustrated in <FIG>) earlier than the main stretchable sections <NUM> and the main stretchable sections <NUM> are in an incompletely spread state (illustrated in <FIG>). The main stretchable sections <NUM> go through the first phase and then the second phase where the main stretchable sections <NUM> are stretched to the elastic limit into a completely spread state (illustrated in <FIG>). In the first phase, the buffer stretchable sections <NUM> having a low elongation at elastic limit are stretched; therefore, a small tension is applied to boundaries between the buffer stretchable sections <NUM> and the non-stretchable regions <NUM> of the elastic film <NUM>. Ruptures of the elastic film <NUM> at the boundaries between the buffer stretchable sections <NUM> and the non-stretchable regions <NUM> are thereby prevented. In the second phase, until the main stretchable sections are in a completely spread state, tension corresponding to the elongation of the main stretchable sections <NUM> is applied to the main stretchable sections <NUM>, the buffer stretchable sections <NUM>, and the non-stretchable regions <NUM>; however, since the buffer stretchable sections <NUM> cannot be stretched any more after the first phase, and tension applied to the non-stretchable regions <NUM> and the buffer stretchable sections <NUM> is entirely supported by the first sheet layer 20A and the second sheet layer 20B. As a result, the tension applied to the boundaries between the buffer stretchable sections <NUM> and the non-stretchable regions <NUM> of the elastic film <NUM> does not exceed the elongation at elastic limit in the first phase. Ruptures of the elastic film <NUM> along the boundaries between the buffer stretchable sections <NUM> and the non-stretchable regions <NUM> are thereby prevented, as in the first phase.

In contrast, if buffer stretchable sections <NUM> are not provided as illustrated in <FIG>, the stretchable region <NUM> has a high elongation at an elastic limit, and tension applied to the boundary between the stretchable region <NUM> and the non-stretchable region <NUM> of the elastic film <NUM> increases until the boundary between the stretchable region <NUM> and the non-stretchable region <NUM> of the elastic film <NUM> is stretched to the elongation at elastic limit into a completely spread state. The elastic film <NUM> is thereby likely to rupture along the boundary between the stretchable region <NUM> and the non-stretchable region <NUM> (the edges of the ruptured elastic film is indicated by the chain double-dashed lines), as illustrated in <FIG>.

In view of the principle described above, it is preferred that the elongation at elastic limit of the buffer stretchable section <NUM> be smaller than a tensile elongation in the stretching and contracting direction of the elastic film <NUM> having a width equal to an interval between two adjacent through holes <NUM> formed in the elastic film <NUM> and arrayed in the direction orthogonal to the stretching and contracting direction and in the non-stretchable region <NUM>, to certainly prevent the rupture of the elastic film <NUM> at the boundary between the stretchable region <NUM> and the non-stretchable region <NUM>.

A shape of each of the sheet bond portions <NUM> and of each of the through holes <NUM> in the natural length state may be set to an arbitrary shape such as a perfect circle, an ellipse, a polygon such as a rectangle (including a linear shape or a rounded corner), a star shape, a cloud shape, etc. A size of each of the sheet bond portions <NUM> may be appropriately determined. At an excessively large size, the hardness of the sheet bondportions <NUM> significantly affects the touch, whereas at an excessively small size, the bonded area is too small to certainly bond the layers. Each of the sheet bond portions <NUM> preferably has an area of approximately <NUM> to <NUM><NUM>, in usual cases. Each of the through holes <NUM> should have an opening area larger than that of the corresponding sheet bond portion <NUM> such that the sheet bond portion <NUM> is formed within the through hole <NUM>. The through hole <NUM> preferably has an opening area of approximately up to <NUM> times the area of the sheet bond portion <NUM>.

In general, the area and the area rate of each of the sheet bond portions <NUM> in each region are preferably set as below.

Area of each of sheet bond portions <NUM>: <NUM> to <NUM><NUM> (particularly <NUM> to <NUM><NUM>).

Area rate of sheet bond portions <NUM>: <NUM> to <NUM>% (particularly <NUM> to <NUM>%).

To produce three fields (i.e., the non-stretchable region <NUM>, the main stretchable section <NUM>, and the buffer stretchable section <NUM>) having different area rates, the number of the sheet bond portions <NUM> per unit area may be varied, as illustrated in <FIG>, or the area of each of the sheet bond portions <NUM> may be varied, as illustrated in <FIG>. In the former case, the areas of the sheet bond portions <NUM> may be the same between two or more fields of the non-stretchable region <NUM>, the main stretchable section <NUM>, and the buffer stretchable section <NUM>, or may be different among all the fields. In the latter case, the number of the sheet bond portions <NUM> per unit area may the same between two or more fields of the non-stretchable region <NUM>, the main stretchable section <NUM>, and the buffer stretchable section <NUM>, or may be different among all the fields.

The planar geometries of the sheet bond portions <NUM> and the through holes <NUM> may be appropriately determined. Preferred is regularly repeated geometry, such as an oblique lattice illustrated in <FIG>, hexagonal lattice (also referred to as staggered lattice) illustrated in <FIG>, square lattice illustrated in <FIG>, rectangular lattice illustrated in <FIG>, or parallelotope lattice illustrated in <FIG> (where two groups of a large number of diagonally parallel arrays intersect each other, as shown in the drawings) (including arrays tilted by less than <NUM> degrees to the stretching and contracting direction). Alternatively, the sheet bond portions <NUM> may be arrayed in regularly repeated groups (the geometry of each group may be regular or irregular, in other words, may be in a pattern or characteristic letters, for example). The geometries of the sheet bond portions <NUM> and the through holes <NUM> may be the same or different among the main stretchable section <NUM>, the buffer stretchable section <NUM>, and the non-stretchable region <NUM>.

As illustrated in <FIG>, in addition to the portion overlapping the absorber <NUM>, for example, it is possible to provide the non-stretchable region <NUM> in which the sheet bond portions <NUM> are disposed in a shape of an indication <NUM>. In this case, the buffer stretchable section may be provided in the stretchable region <NUM> continuing from the non-stretchable region <NUM>. The indication <NUM> may correspond to an indication known in a field of the absorbent article, for example, a pattern for decoration (including a tiny picture or a character), a function indicator such as a usage method, usage assistance, a size, etc., or a mark indication such as a manufacturer, a product name, a characteristic function, etc. In an illustrated mode, the applied indication <NUM> is a flower pattern corresponding to a plant pattern. However, it is possible to use various types of patterns such as an abstract pattern, an animal pattern, and a natural phenomenon pattern.

The elastic film <NUM> may be composed of any resin film having elasticity. For example, it is possible to use a film obtained by processing a blend of one or two or more types of thermoplastic elastomers such as a styrene type elastomer, an olefin type elastomer, a polyester type elastomer, a polyamide type elastomer, a polyurethane type elastomer, etc. in a film shape using extrusion molding such as a T-die method, an inflation method, etc. In addition, it is possible to use a film in which a large number of holes or slits are formed for ventilation in addition to a nonporous film. In particular, it is preferable when the elastic film <NUM> has a tensile strength in the stretching and contracting direction of <NUM> to <NUM> N/<NUM>, tensile strength in the direction orthogonal to the stretching and contracting direction of <NUM> to <NUM> N/<NUM>, tensile elongation in the stretching and contracting direction of <NUM> to <NUM>,<NUM>%, and tensile elongation in the direction orthogonal to the stretching and contracting direction of <NUM> to <NUM>,<NUM>%. The thickness of the elastic film <NUM> is not particularly restricted. However, the thickness is preferably in a range of about <NUM> to <NUM>. In addition, the basis weight of the elastic film <NUM> is not particularly restricted. However, the basis weight is preferably in a range of about <NUM> to <NUM>/m<NUM>, and particularly preferably in a range of about <NUM> to <NUM>/m<NUM>.

Characteristically, as illustrated in <FIG>, the first sheet layer 20A and the second sheet layer 20B in the sheet bond portions <NUM> are joined at least by a melted and solidifiedmaterial <NUM> of the elastic film <NUM> among the first sheet layer 20A and the second sheet layer 20B. When the first sheet layer 20A and the second sheet layer 20B are joined using the melted and solidified material <NUM> of the elastic film <NUM> as an adhesive in this way, a peeling strength becomes high, and it is possible to achieve both high air permeability and high peeling strength as understood from Example below.

In such a joining structure, for example, as illustrated in <FIG>, when welding is performed in a predetermined pattern of the sheet bond portions <NUM> in a state in which the elastic film <NUM> is interposed between the first sheet layer 20A and the second sheet layer 20B while being stretched in the stretching and contracting direction, the elastic film <NUM> may be melted at a large number of positions to form the through holes <NUM>, and manufacture may be simply and efficiently performed using a method of joining the first sheet layer 20A and the second sheet layer 20B by at least solidification of the melted material of the elastic film <NUM> at positions of the through holes <NUM>. In this case, in the natural length state, the shape/area of each of the sheet bond portions <NUM> are substantially equal to the shape/area of each of the through holes <NUM>. <FIG> illustrates an example using a heat sealing device. A material to be processed, while in the material, the elastic film <NUM> is interposed between the first sheet layer 20A and the second sheet layer 20B, is fed between a seal roll <NUM> having a large number of pressing protrusions 60p arranged in the above pattern of the sheet bond portions <NUM> on an outer surface thereof and an anvil roll <NUM> which is disposed to face the seal roll <NUM> and has a smooth surface, and the pressing protrusions 60p are heated. In this way, the elastic film <NUM> is melted only where pressed in the thickness direction between the pressing protrusions 60p and an outer surface of the anvil roll <NUM> to form the through holes <NUM>, and the first sheet layer 20A and the second sheet layer 20B are joined at least by the solidification of the melted material of the elastic film <NUM> at the positions of the through holes <NUM>. However, another device such as ultrasonic sealing may be used as long as the elastic film <NUM> is melted in a desired pattern to form the through holes <NUM>, and the first sheet layer 20A and the second sheet layer 20B are joined at least by solidification of the melted material of the elastic film <NUM> at the positions of the through holes <NUM>.

It is possible to appropriately determine a relation of a melting point of the elastic film <NUM>, melting points of the first sheet layer 20A and the second sheet layer 20B, and a processing temperature at a welding position. However, rather than to set the melting points of the first sheet layer 20A and the second sheet layer 20B to be lower than or equal to the melting point of the elastic film <NUM>, melt and combine the whole of the first sheet layer 20A and the second sheet layer 20B and the whole elastic film <NUM> at the welding positions, and form the sheet bond portions <NUM>, it is preferable to set the melting points of the first sheet layer 20A and the second sheet layer 20B to be higher than the melting point of the elastic film <NUM>, melt the elastic film <NUM> at the welding position, and not to melt a part of the first sheet layer 20A and the second sheet layer 20B or not to melt a whole of the first sheet layer 20A and the second sheet layer 20B. In other words, as understood from <FIG> and <FIG>, a latter case corresponds to a structure in which fibers 20f of the first sheet layer 20A and the second sheet layer 20B continuing from around the sheet bond portions <NUM> are left, and the first sheet layer 20A and the second sheet layer 20B are joined by the melted and solidified material <NUM> of the elastic film <NUM>, which has infiltrated and solidified among the first sheet layer 20A and the second sheet layer 20B. Further, improved adhering of the melted and solidified material of the elastic film to the first sheet layer and the second sheet layer is obtained, and strength of the first sheet layer 20A and the second sheet layer 20B rarely decreases. Thus, peeling strength is further enhanced. This situation in which "a part of the first sheet layer 20A and the second sheet layer 20B is not melted" includes a mode in which for all fibers of the sheet bond portions, a core (including a central portion of each component fiber of a conjugate fiber in addition to a core of the conjugate fiber) remains while a surrounding portion (including a portion on a surface layer side of each component fiber of a conjugate fiber in addition to a sheath in the conjugate fiber) melts; a mode in which some fibers do not melt at all while all remaining fibers melt or a core remains while a surrounding portion melts.

From this point of view, the melting point of the elastic film <NUM> is preferably about <NUM> to <NUM>, the melting points of the first sheet layer 20A and the second sheet layer 20B are preferably about <NUM> to <NUM>, particularly, <NUM> to <NUM>, and a difference between the melting points of the first sheet layer 20A and the second sheet layer 20B and the melting point of the elastic film <NUM> is preferably about <NUM> to <NUM>.

In the illustrated example, the elastic film stretchable structure 20X is applied to a stretchable structure, which is provided in the outer body <NUM> excluding the waist end portion region. However, appropriate changes are allowed. For example, the waist end portion region may be included to which the elastic film stretchable structure 20X is applied as in modes illustrated in <FIG> described below, or it is possible to adopt a mode in which the elastic film stretchable structure 20X is not provided in the intermediate region L between the torso region T of the front body F and the torso region T of the back body B. In addition, the above-described stretchable structure 20X may be applied to another elastic portion such as a three-dimensional gather, a plane gather, etc. generally used for a waist, a fastening tape, and an absorbent article of a tape-type disposable diaper in addition to the underpants-type disposable diaper. In addition, even though the non-stretchable region is included in the present embodiment, it is possible to adopt a mode in which the whole elastic film stretchable structure is used as the stretchable region and the non-stretchable region is not included. Furthermore, even though the stretching and contracting direction is regarded as the width direction in the illustrated example, the stretching and contracting direction may be set to the front-back direction or set to both the width direction and the front-back direction.

The first sheet layer and second sheet layer used were spun bond nonwoven fabric having a basis weight of <NUM>/m<NUM> made of PE/PP conjugate fiber (core: polypropylene (melting point, <NUM>), sheath: polyethylene (melting point, <NUM>)). The elastic film used had a basis weight of <NUM>/m<NUM>, thickness of <NUM>, and a melting point in the range of <NUM> to <NUM>. The elastic film in a natural length state (the natural state or stretched state does not affect the relative comparison of the peel strength) was disposed between the first and second sheet layers in the same machine direction (MD). With reference to <FIG>, rectangular sheet bond portions <NUM> having long sides in the MD (short side: <NUM>, long side: <NUM>) are formed at an interval of <NUM> in the cross direction (CD) perpendicular to the MD and an interval of <NUM> in the MD with a stapler-type ultrasonic sealing machine (HARURU SUH-<NUM> available from SUZUKI). A sample <NUM> provided with the elastic film having a CD length 100y of <NUM> and a MD length 100x of <NUM> was thereby produced (inventive example). The same operator carried out ultrasonic sealing for a pressuring time of about three seconds under the same pressure also for obtaining a similar joining state to that in the photograph illustrated in <FIG>. The MD of the nonwoven fabric represents the direction of the orientation of the nonwoven fabric (the fibers of the nonwoven fabric are oriented in the MD), and can be determined, for example, by a method of testing the orientation of fiber by a zero-distance tensile strength in accordance with a TAPPI standard T481 or a simplified testing methods that determines the direction of the orientation from the ratio of the tensile strengths of the front-back direction to the width direction.

A sample was prepared in the same way as in the inventive example except a double layered structure free from the elastic film was used (comparative example). The structure of the sample free from the elastic film is regarded as the structure shown in Patent Literature <NUM> in which the first sheet layer is joined to second sheet layer without an elastic film, in terms of peel strength.

With reference to <FIG>, the first and second sheet layers were each manually peeled by a length 101z, <NUM>, from one end in the CD, each of the samples <NUM> has the laminated stretchable structures, the released portions <NUM> were clamped with chucks for a tensile tester, and peeling of the remaining <NUM> of the first and second sheet layers was re-started from the above mentioned <NUM> position at a chuck interval of <NUM> and a speed of testing of <NUM>/min in the stretching and contracting direction. The observed maximum tensile stress was defined as peel strength. The testing machine was a universal TENSILON tester RTC-1210A available from ORIENTEC.

The results demonstrate that the inventive sample has a significantly high peel strength of <NUM>. 2N, whereas the comparative sample has a peel strength of <NUM>.

Now, a mode, which is not according to the invention, for solving the second problem will be described with reference to <FIG> and <FIG>. As long as the outer body <NUM> is extended to a lateral side of the side edge of the absorber <NUM>, in the crotch portion, a side edge of the outer body <NUM> may be positioned closer to a central side than a side edge of the inner body <NUM> in the width direction as in the illustrated mode, or may be positioned closer to an outer side than that in the width direction. The outer body <NUM> has torso regions T each defined by a front-back direction range corresponding to a range of the side seal portion <NUM>, and an intermediate region L corresponding to a front-back direction range between the torso region T of the front body F and the torso region T of the back body B. Further, in the outer body <NUM> of the illustrated mode, except for the middle of the intermediate region L in the front-back direction, an elastic film <NUM> is stacked between a first sheet layer 20A and a second sheet layer 20B as illustrated in <FIG>, and the first sheet layer 20A and the second sheet layer 20B have an elastic film stretchable structure 20X with a stretching and contracting direction in the width direction, and they are joined via through holes <NUM> penetrating the elastic film <NUM> at a large number of sheet bond portions <NUM> arranged at intervals as illustrated in <FIG>. A planar shape of the outer body <NUM> is formed by a concave leg line <NUM> such that each of both side edges of the intermediate region L in the width direction forms a leg opening, and corresponds to a pseudo-hourglass shape as a whole. The outer body <NUM> may be divided into two front and back parts, and the both parts may be separated from each other in the front-back direction in the crotch portion.

The modes, which are not according to the invention, illustrated in <FIG> and <FIG> correspond to a mode in which the elastic film stretchable structure 20X extends to the waist end portion region <NUM>. However, when the elastic film stretchable structure 20X is used in the waist end portion region <NUM>, tightening of the waist end portion region <NUM> is insufficient. It is possible to provide a stretchable structure according to a conventional elongated waist portion elastic member <NUM> as necessary without providing the elastic film stretchable structure 20X in the waist end portion region <NUM> as the modes illustrated in <FIG> and <FIG>. The waist portion elastic members <NUM> correspond to elongated elastic members such as a plurality of rubber threads disposed at intervals in the front-back direction, and apply a stretching force to tighten around the waist of the body. The waist portion elastic members <NUM> are not disposed substantially in a bundle with a close spacing, and three or more, preferably five or more members are disposed at intervals of about <NUM> to <NUM> to form a predetermined stretchable zone. A stretch rate of the waist portion elastic member <NUM> in fixing may be appropriately determined. However, the stretch rate may be set to about <NUM> to <NUM>% in the case of normal adult use. Rubber threads are used as the waist portion elastic member <NUM> in an illustrated example. However, for example, another elongated elastic member such as flat rubber may be used.

As another mode, although not illustrated, the elastic film stretchable structure 20X may not be provided in the intermediate region L between the torso region T of the front body F and the torso region T of the back body B, the stretchable structure 20X may be continuously provided in the front-back direction from the inside of the torso region T of the front body F to the inside of the torso region T of the back body B through the intermediate region L, or the elastic film stretchable structure 20X may be provided only in any one of the front body F and the back body B.

A shape of each of the sheet bond portions <NUM> and the through holes <NUM> in a natural length state may be appropriately determined. However, it is possible to adopt an arbitrary shape such as a perfect circle (see <FIG> and <FIG>), an ellipse, a polygon such as a triangle, a rectangle (see <FIG>), a rhombus (see <FIG>), etc., a convex lens shape (see <FIG>), a concave lens shape (see <FIG>), a star shape, a cloud shape, etc. The dimensions of each of the sheet bond portions are not particularly restricted. However, a maximum length 40x is preferably set to <NUM> to <NUM>, particularly <NUM> to <NUM>, and a maximum width is preferably set to <NUM> to <NUM>, particularly <NUM> to <NUM> in a case of a shape which is long in a direction orthogonal to the stretching and contracting direction.

A size of each of the sheet bond portions <NUM> may be appropriately determined. However, when the size is excessively large, an influence of hardness of the sheet bond portions <NUM> on a sense of touch increases. When the size is excessively small, a joining area is small, and materials may not be sufficiently attached to each other. Thus, in general, an area of each of the sheet bond portions <NUM> is preferably set to about <NUM> to <NUM><NUM>. An area of an opening of each of the through holes <NUM> may be greater than or equal to that of the sheet bond portions since the sheet bond portions are formed via the through holes <NUM>. However, the area is preferably set to about <NUM> to <NUM> times the area of each of the sheet bond portions. The area of the opening of each of the through holes <NUM> refers to a value in a natural length state and in a state of being integrated with the first sheet layer 20A and the second sheet layer 20B rather than a state of the elastic film <NUM> alone, and refers to a minimum value in a case in which the area of the opening of each of the through holes <NUM> is not uniform in a thickness direction such as a case in which the area is different between a front and a back of the elastic film <NUM>.

The planar geometries of the sheet bond portions <NUM> and the through holes <NUM> may be appropriately determined as stated before. Preferred is regularly repeated geometry, such as an oblique lattice illustrated in <FIG>, hexagonal lattice (also referred to as staggered lattice) illustrated in <FIG>, square lattice illustrated in <FIG>, rectangular lattice illustrated in <FIG>, or parallelotope lattice illustrated in <FIG> (where two groups of a large number of diagonally parallel arrays intersect each other, as shown in the drawings) (including arrays tilted by less than <NUM> degrees to the stretching and contracting direction). Alternatively, the sheet bond portions <NUM> may be arrayed in regularly repeated groups (the geometry of each group may be regular or irregular, in other words, may be in a pattern or characteristic letters, for example).

In the sheet bond portions <NUM>, the first sheet layer 20A and the second sheet layer 20B are joined via the through holes <NUM> formed in the elastic film <NUM>. In this case, it is preferable that the first sheet layer 20A is not and the second sheet layer 20B is not joined to the elastic film <NUM> in a portion other than at least between the first sheet layer 20A and the second sheet layer 20B in the sheet bond portions <NUM>.

Joining means for the first sheet layer 20A and the second sheet layer 20B in the sheet bond portions <NUM> is not particularly restricted. For example, the first sheet layer 20A and the second sheet layer 20B in the sheet bond portions <NUM> may be joined using a hot-melt adhesive or joining means based on material welding such as heat sealing, ultrasonic sealing, etc..

As a mode in which the sheet bond portions <NUM> are formed by material welding, it is possible to adopt any one of a first welding mode (see <FIG>) in which the first sheet layer 20A and the second sheet layer 20B are joined only by a melted and solidified material <NUM> corresponding to a most part or a part of at least one of the first sheet layer 20A and the second sheet layer 20B in the sheet bond portions <NUM>; a second welding mode (see <FIG>) in which the first sheet layer 20A and the second sheet layer 20B are joined only by a melted and solidified material <NUM> corresponding to a whole, a most part, or a part of the elastic film <NUM> in the sheet bond portions <NUM>; and a third welding mode (see <FIG>) obtained by combining these welding modes, and it is preferable to adopt the second and third welding modes. A particularly preferable mode is a mode in which the first sheet layer 20A and the second sheet layer 20B are joined by the melted and solidified material <NUM> corresponding to a part of the first sheet layer 20A and the second sheet layer 20B and the melted and solidified material <NUM> corresponding to a whole or a most part of the elastic film <NUM> in the sheet bond portions <NUM>. The melted and solidified material <NUM> of the elastic film <NUM> appearing in white is seen in the melted and solidified material <NUM> with the fibers of the first sheet layer 20A or the second sheet layer 20B appearing in black in the third welding mode illustrated in <FIG>, however, the melted and solidified material of the elastic film is not seen in the melted and solidified material <NUM> with the fibers of the first sheet layer 20A or the second sheet layer 20B in the first welding mode illustrated in <FIG> (a while part corresponds to scattered reflection of boundary of the melted and solidified material <NUM> with the fibers and the melted and solidified material <NUM> with the fibers).

In a case in which the first sheet layer 20A and the second sheet layer 20B are joined using the melted and solidified material <NUM> corresponding to a most part or a part of at least one of the first sheet layer 20A and the second sheet layer 20B as an adhesive as in a first adhesive mode or a third adhesive mode, it is preferable that a part of the first sheet layer 20A and the second sheet layer 20B is not melted in order not to harden the sheet bond portions <NUM>. This situation in which "a part of the first sheet layer 20A and the second sheet layer 20B is not melted" includes, in a case that the first sheet layer 20A is composed of a nonwoven fabric and the second sheet layer 20B is composed of a nonwoven fabric, a mode in which for all fibers of the sheet bond portions <NUM>, a core (including a central portion of each component fiber of a conjugate fiber in addition to a core of the conjugate fiber) remains while a surrounding portion (including a portion on a surface layer side of each component fiber of a conjugate fiber in addition to a sheath in the conjugate fiber) melts; a mode in which some fibers do not melt at all while all remaining fibers melt; or a mode in which a core remains while a surrounding portion melts.

Peeling strength becomes high when the first sheet layer 20A and the second sheet layer 20B are bonded using the melted and solidified material <NUM> of the elastic film <NUM> as an adhesive as in the second welding mode and the third welding mode. In the second welding mode, under the condition that a melting point of at least one of the first sheet layer 20A and the second sheet layer 20B is higher than a melting point of the elastic film <NUM> and a heating temperature at the time of forming the sheet bond portions <NUM>, the elastic film <NUM> may be interposed between the first sheet layer 20A and the second sheet layer 20B, a part corresponding to the sheet bond portions <NUM> may be pressed and heated, and only the elastic film <NUM> may be melted, thereby performing manufacture. Meanwhile, in the third welding mode, under the condition that a melting point of at least one of the first sheet layer 20A and the second sheet layer 20B is higher than the melting point of the elastic film <NUM>, the elastic film <NUM> may be interposed between the first sheet layer 20A and the second sheet layer 20B, the part corresponding to the sheet bond portions <NUM> may be pressed and heated, and at least one of the first sheet layer 20A and the second sheet layer 20B and the elastic film <NUM> may be melted, thereby performing manufacture. From this point of view, the melting point of the elastic film <NUM> is preferably about <NUM> to <NUM>, melting points of the first sheet layer 20A and the second sheet layer 20B are preferably about <NUM> to <NUM>, particularly, <NUM> to <NUM>, and a difference between the melting points of the first sheet layer 20A and the second sheet layer 20B and the melting point of the elastic film <NUM> is preferably about <NUM> to <NUM>. In addition, the heating temperature is preferably set to <NUM> to <NUM>.

In the second welding mode and the third welding mode, when the first sheet layer 20A and the second sheet layer 20B are nonwoven fabric, the melted and solidified material <NUM> of the elastic film <NUM> may infiltrate among fibers over the whole thickness direction of the first sheet layer 20A and the second sheet layer 20B of the sheet bond portions <NUM> as illustrated in <FIG>. However, flexibility of the sheet bond portions <NUM> becomes high in a mode in which the melted and solidified material <NUM> infiltrates among fibers in the thickness direction halfway as illustrated in <FIG>, and <FIG>, or a mode in which the melted and solidified material <NUM> hardly infiltrate among the fibers of the first sheet layer 20A and the second sheet layer 20B as illustrated in <FIG>.

<FIG> illustrates an example of an ultrasonic sealing device suitable for forming the second welding mode and the third welding mode. In this ultrasonic sealing device, to form bond portions <NUM>, the first sheet layer 20A, the elastic film <NUM>, and the second sheet layer 20B are fed between an ultrasonic horn <NUM> and an anvil roll <NUM> having a pattern of protrusions 60a of the sheet bond portions <NUM> on an external surface. In this instance, for example, when a feed speed transferring the elastic film <NUM> at an upstream side by a feed drive roll <NUM> and a nip roll <NUM> is controlled to be lower than a feed speed for transferring after the anvil roll <NUM> and the ultrasonic horn <NUM>, the elastic film <NUM> is stretched to a predetermined stretch rate in an MD (machine direction, flow direction) on a path from a nip position by the feed drive roll <NUM> and the nip roll <NUM> to a sealing position by the anvil roll <NUM> and the ultrasonic horn <NUM>. A stretch rate of the elastic film <NUM> may be determined by controlling a speed difference between the anvil roll <NUM> and the feed drive roll <NUM>, and may be set to, for example, about <NUM>% to <NUM>%. Reference symbol <NUM> denotes the nip roll. The first sheet layer 20A, the elastic film <NUM>, and the second sheet layer 20B fed between the anvil roll <NUM> and the ultrasonic horn <NUM> are, in a stacked state in this order, heated by ultrasonic vibration energy of the ultrasonic horn <NUM> while being pressed between the protrusions 60a and the ultrasonic horn <NUM>. Further, the through holes <NUM> are formed in the elastic film <NUM> by melting only the elastic film <NUM> or melting the elastic film <NUM> and at least one of the first sheet layer 20A and the second sheet layer 20B. At the same time, the first sheet layer 20A and the second sheet layer 20B are joined via the through holes <NUM>. Therefore, in this case, an area rate of the sheet bond portions <NUM> may be selected by selecting a size, a shape, a separation interval, an arrangement pattern in a roll length direction and a roll circumferential direction, etc. of the protrusions 60a of the anvil roll <NUM>.

Although the reason for formation of the through holes <NUM> is not necessarily clear, it is considered that openings are formed by melting the elastic film <NUM> at corresponding sites to the protrusions 60a of the anvil roll <NUM> so as to be removed from the surroundings. In this instance, a portion between each pair of adjacent through holes <NUM> arranged in the stretching and contracting direction in the elastic film <NUM> is cut from portions at both sides in the stretching and contracting direction by the through holes <NUM> as illustrated in <FIG>, <FIG>, and <FIG>, and support at both sides in a contraction direction is lost. Thus, in a range in which continuity in a direction orthogonal to the contraction direction can be maintained, the closer to the central side of a direction orthogonal to the stretching and contracting direction, the more elastic film <NUM> contracts to match with the central side in the stretching and contracting direction so that the through holes <NUM> are enlarged in the stretching and contracting direction. When the sheet bond portions <NUM> are formed in a pattern with a section being left in which the elastic film <NUM> linearly continues along the stretching and contracting direction, as in the stretchable region <NUM> explained after, the elastic film <NUM> contracts to the natural length state for example by cutting for obtaining individual products, an enlarged portion of each through hole <NUM> contracts in the stretching and contracting direction so that a gap cannot be formed between each through hole <NUM> and each sheet bond portion <NUM> as illustrated in <FIG> and <FIG>. On the other hand, when the sheet bond portions <NUM> are formed in a pattern without such a section in which the elastic film <NUM> linearly continues along the stretching and contracting direction, as in the non-stretchable region <NUM> explained after, even if the elastic film <NUM> is cut for obtaining the individual products, contraction is not substantially performed, as illustrated in <FIG>. Thus, a large gap is left between each through hole <NUM> and each sheet bond portion <NUM>.

The first sheet layer 20A and the second sheet layer 20B may be composed of any sheet members, preferably nonwoven fabrics in view of air permeability and flexibility. The nonwoven fabric may be composed of any raw fiber. Examples of the raw fiber include synthetic fibers, such as olefin fibers, e.g., polyethylene fibers and polypropylene fibers, polyester fibers, and polyamide fibers; recycled fibers, such as rayon and cupra; natural fibers, such as cotton; and blend or conjugate fibers composed of two or more of these fibers. The nonwoven fabric may be prepared by any process. Examples of such a process include well-known processes, such as spun lacing, spun bonding, thermal bonding, melt blowing, needle punching, air-through processes, and point bonding. The nonwoven fabric preferably has a basis weight of approximately <NUM> to approximately <NUM>/m<NUM>. The first sheet layer 20A and the second sheet layer 20B may be composed of a pair of facing layers prepared by folding back a single sheet that is partially or entirely folded back. For example, as in the illustrated mode, in the waist end portion region <NUM>, a component located outer side may be used as the second sheet layer 20B, the folded part 20C formed by folding back to the internal surface side at the waist opening edge thereof may be used as the first sheet layer 20A, and the elastic film <NUM> may be interposed therebetween, and in the rest part, a component located inner side may be used as the first sheet layer 20A, another component located outer side may be used as the second sheet layer 20B, and the elastic film <NUM> may be interposed therebetween. The component of the first sheet layer 20A and the component of the second sheet layer 20B may be separately provided across the whole part in the front-back direction, and the elastic film <NUM> may be interposed between the component of the first sheet layer 20A and the component of the second sheet layer 20B without folding back the component members.

The elastic film <NUM> may be composed of any thermoplastic resin film having elasticity. For example, it is possible to use a film in which a large number of holes or slits are formed for ventilation in addition to a nonporous film. In particular, it is preferable when the elastic film <NUM> has a tensile strength in the width direction (the stretching and contracting direction, the MD) of <NUM> to <NUM> N/<NUM>, tensile strength in the front-back direction (the direction orthogonal to the stretching and contracting direction, the CD) of <NUM> to <NUM> N/<NUM>, tensile elongation in the width direction of <NUM> to <NUM>,<NUM>%, and tensile elongation in the front-back direction of <NUM> to <NUM>,<NUM>%. The thickness of the elastic film <NUM> is not particularly restricted. However, the thickness is preferably in a range of about <NUM> to <NUM>.

A region having the elastic film stretchable structure 20X in the outer body <NUM> includes the non-stretchable region <NUM> and the stretchable region <NUM> stretchable in the width direction provided at least at one side of the non-stretchable region <NUM> in the width direction. Arrangement of the stretchable region <NUM> and the non-stretchable region <NUM> may be appropriately determined. In the case of the outer body <NUM> of the underpants-type disposable diaper as in the present embodiment, a portion overlapping the absorber <NUM> is a region that may not be stretched or contracted. Thus, a part or a whole of the portion overlapping the absorber <NUM> (desirably including substantially the whole internal and external fixed region 10B) is preferably set to the non-stretchable region <NUM> as in the illustrated mode. The non-stretchable region <NUM> may be provided from a region overlapping the absorber <NUM> to a region not overlapping the absorber <NUM> positioned in the width direction or the front-back direction thereof, and the non-stretchable region <NUM> may be provided only in the region not overlapping the absorber <NUM>.

The stretchable region <NUM> has a section <NUM> in which the elastic film <NUM> linearly continues along the width direction, contracts in the width direction due to a contraction force of the elastic film <NUM>, and is stretchable in the width direction. More specifically, the whole elastic film stretchable structure 20X including both the stretchable region <NUM> and the non-stretchable region <NUM> is formed by joining the first sheet layer 20A and the second sheet layer 20B via the through holes <NUM> of the elastic film <NUM> to form a large number of sheet bond portions <NUM> at intervals in the width direction and the front-back direction orthogonal thereto (the direction orthogonal to the stretching and contracting direction) while the elastic film <NUM> is stretched in the width direction. Further, in the stretchable region <NUM>, the through holes <NUM> may be disposed to have the section in which the elastic film <NUM> linearly continues along the width direction, thereby imparting elasticity.

In the stretchable region <NUM>, as illustrated in <FIG> and <FIG>, when the elastic film <NUM> is in the natural length state, the first sheet layer 20A and the second sheet layer 20B between the sheet bond portions <NUM> stretch in a direction away from each other, and thus a contraction wrinkle <NUM> extending in the front-back direction is formed. In a worn state in which the elastic film <NUM> is stretched to an extent in the width direction, as illustrated in <FIG> and <FIG>, the contraction wrinkles <NUM> are still remain although the contraction wrinkles <NUM> are stretched. In addition, as in the illustrated mode, when the first sheet layer 20A is not and the second sheet layer 20B is not joined to the elastic film <NUM> in a portion other than at least between the first sheet layer 20A and the second sheet layer 20B in the sheet bond portions <NUM>, as understood from <FIG> and <FIG> assuming the worn state and <FIG> and <FIG> assuming a spread state of the first sheet layer 20A and the second sheet layer 20B, a gap is formed between each through hole <NUM> of the elastic film <NUM> and the sheet bond portions <NUM> and in these states, and air permeability is imparted due to the gap even when a material of the elastic film <NUM> corresponds to a non-porous film or a sheet. In addition, when the elastic film <NUM> is in the natural length state illustrated in <FIG> and <FIG>, the through holes <NUM> are narrowed by contraction of the elastic film <NUM>, and a gap is hardly formed between each through hole <NUM> and the sheet bond portions <NUM>. States of the contraction wrinkle <NUM> in the worn state and the natural length state are shown in reference sample photographs of <FIG> and <FIG> (sample in which a vent hole <NUM> is not formed).

An elongation at an elastic limit of the stretchable region <NUM> in the width direction is desirably set to <NUM>% or more (preferably <NUM>% to <NUM>%). The elongation at the elastic limit of the stretchable region <NUM> is substantially determined by the stretch rate of the elastic film <NUM> in the manufacturing. However, the elongation at the elastic limit decreases due to a factor that inhibits contraction in the width direction based thereon. A main inhibition factor corresponds to a ratio of the length 40x of the sheet bond portions <NUM> to a unit length in the width direction. As this ratio increases, the elongation at the elastic limit decreases. In general, since the length 40x of each of the sheet bond portions <NUM> correlates with the area rate of the sheet bond portions <NUM>, the elongation at the elastic limit of the stretchable region <NUM> may be adjusted by the area rate of the sheet bond portions <NUM>.

Stretching stress of the stretchable region <NUM> may be adjusted mainly by a sum of widths 32w of sections <NUM> in each of which the elastic film <NUM> linearly continues along the width direction. The width 32w of the section <NUM> in which the elastic film <NUM> linearly continues along the width direction is equal to an interval 31d of the through holes <NUM> coming into contact with both side edges of the continuing portion <NUM> in the front-back direction. The interval 31d of the through holes <NUM> is equal to an interval 40d of the sheet bond portions <NUM> coming into contact with the both side edges of the continuing sections in the front-back direction when the length 31y of the through hole <NUM> in the front-back direction is equal to the length 40y of the sheet bond portion <NUM> in the front-back direction (when a scheme of simultaneously forming the through holes <NUM> and the sheet bond portions <NUM> described above is adopted). Therefore, in this case, the stretching stress of the stretchable region <NUM> may be adjusted by a ratio of the length 40y of each of the sheet bond portions <NUM> to a unit length in the front-back direction. In general, since the length 40y of each of the sheet bond portions <NUM> correlates with the area rate of the sheet bond portions <NUM>, the stretching stress of the stretchable region <NUM> maybe adjusted by the area rate of the sheet bond portions <NUM>. Stretching stress in stretching to an elastic limit of <NUM>% may be estimated as the stretching stress of the stretchable region <NUM>.

The area rate of the sheet bond portions <NUM> and the area of each of the sheet bond portions <NUM> in the stretchable region <NUM> may be appropriately determined. However, in general, the area rate and the areas are preferably set within the following ranges.

As described above, the elongation at the elastic limit and the stretching stress of the stretchable region <NUM> may be adjusted by the area of each of the sheet bond portions <NUM>. Thus, as illustrated in <FIG>, it is possible to provide a plurality of regions having different area rates of the sheet bond portions <NUM> in the stretchable region <NUM>, and to change fitness according to a part. In a mode illustrated in <FIG>, in the front body F, regions <NUM> each extending in an oblique direction along a base of the leg and edge portion regions <NUM> of the leg openings have respectively, when compared to other regions, higher area rates of the sheet bond portions <NUM>, and thus have smaller stretching stresses, resulting in abilities to stretch flexibly. In addition, in the back body B, ilium facing regions <NUM> and the edge portion regions <NUM> of the leg openings have, when compared to other regions, high area rates of the sheet bond portions <NUM>, and thus have small stretching stresses, resulting in abilities to stretch flexibly.

Meanwhile, the non-stretchable region <NUM> is configured, even through the elastic film <NUM> continues in the width direction, so as not to have a section in which the elastic film <NUM> linearly continues along the width direction, due to the presence of the through holes <NUM>. Therefore, even though the elastic film stretchable structure 20X is configured as a whole to include both the stretchable region <NUM> and the non-stretchable region <NUM> by joining the first sheet layer 20A and the second sheet layer 20B via the through holes <NUM> of the elastic film <NUM> to form the large number of sheet bond portions <NUM> at intervals in the width direction and the front-back direction orthogonal thereto while the elastic film <NUM> is stretched in the width direction, in the non-stretchable region <NUM> , the elastic film <NUM> does not linearly continue along the width direction as illustrated in <FIG>. Thus, the contraction force of the elastic film <NUM> hardly acts on the first sheet layer 20A and the second sheet layer 20B, elasticity is almost lost, and the elongation at the elastic limit approaches <NUM>%. Further, in the non-stretchable region <NUM>, the first sheet layer 20A and the second sheet layer 20B are joined by the large number of sheet bond portions <NUM> arranged at intervals, and the sheet bond portions <NUM> are discontinuous. Thus, a decrease in flexibility is prevented. In other words, it is possible to form the stretchable region <NUM> and the non-stretchable region <NUM> depending on the presence or absence of a section in which the elastic film <NUM> does not linearly continue along the width direction. In addition, continuity of the elastic film <NUM> remains in the non-stretchable region <NUM>. As understood from a reference sample photograph (sample in which a vent hole <NUM> is not formed) illustrated in <FIG>, since an independent cut piece of the elastic film <NUM> is not left, and no wrinkle is formed, appearance is extremely excellent, and air permeability in the thickness direction by the through holes <NUM> is ensured. In the non-stretchable region <NUM>, the elongation at elastic limit in the width direction is preferably <NUM>% or less (preferably <NUM>% or less, more preferably <NUM>%).

An arrangement pattern of the through holes <NUM> in the elastic film <NUM> in the non-stretchable region <NUM> may be appropriately determined. However, when staggered arrangement is adopted as illustrated in <FIG>, and a pattern in which a center interval 31e of the through holes <NUM> in the front-back direction is shorter than the length 31y of each of the through holes <NUM> in the front-back direction is adopted, linear continuity in the width direction may be almost completely eliminated while maintaining continuity of the elastic film <NUM>, and appearance is preferable as illustrated in <FIG>. In this case, it is more preferable that a center interval 31f of the through holes <NUM> in the width direction is shorter than a length 31x of each of the through holes <NUM> in the width direction.

In general, especially when stretching stress is in a range of <NUM> to <NUM> N/<NUM> in stretching the elastic film <NUM> four times in the width direction, in a state in which the non-stretchable region <NUM> is stretched to the elastic limit in the width direction, the center interval 31e of the through holes <NUM> in the front-back direction is preferably in a range of <NUM> to <NUM>, and the length 31y of each of the through holes <NUM> in the front-back direction is preferably in a range of <NUM> to <NUM>, particularly in a range of <NUM> to <NUM>. In addition, the center interval 31f of the through holes <NUM> in the width direction is preferably <NUM> to <NUM> times, particularly <NUM> to <NUM> times the length 31y of the through holes <NUM> in the front-back direction, and the length 31x of each of the through holes <NUM> in the width direction is preferably <NUM> to <NUM> times, particularly <NUM> to <NUM> times the center interval 31f of the through holes <NUM> in the width direction. In a state in which the non-stretchable region <NUM> is stretched to an elastic limit in the width direction (in other words, in a state in which the first sheet layer 20A and the second sheet layer 20B are completely spread), the center interval 31f of the through holes <NUM> in the width direction is equal to a center interval 40f of the sheet bond portions <NUM> in the width direction, the center interval 31e of the through holes <NUM> in the front-back direction is equal to a center interval 40e of the sheet bond portions <NUM> in the front-back direction, and the length 31y of each of the through holes <NUM> in the front-back direction is equal to the length 40y of each of the sheet bond portions <NUM> in the front-back direction.

In a case in which the first sheet layer 20A is not and the second sheet layer 20B is not joined to the elastic film <NUM> in a portion other than between the first sheet layer 20A and the second sheet layer 20B in the sheet bond portions <NUM> in the non-stretchable region <NUM>, and gaps, which are generated by the peripheral edge of each of the through holes <NUM> of the elastic film <NUM> and each of the sheet bond portions <NUM> separated from each other, are included at both sides of each of the sheet bond portions <NUM> in the width direction in the natural length state, air permeability is imparted at all times due to the gaps even if the material of the elastic film <NUM> is a non-porous film or a non-porous sheet, and thus the case is preferable. In the case of adopting a scheme of simultaneously forming the through holes <NUM> and the sheet bond portions <NUM> described above, this state is automatically obtained irrespective of a shape of the sheet bond portions <NUM>.

The shape of each of the sheet bond portions <NUM> and the through holes <NUM> in the natural length state is not particularly restricted. However, it is desirable to have a small area from a viewpoint of flexibility, and it is desirable to have a shape which is long in the front-back direction to eliminate linear continuity in the width direction of the elastic film <NUM>. Thus, it is preferable to adopt an ellipse which is long in the front-back direction, a rectangle (see <FIG>), the rhombus (see <FIG>, the convex lens shape (see <FIG>), and the concave lens shape (see <FIG>). However, when corners are acute as in the rhombus, the elastic film <NUM> is easily fractured. In contrast, the convex lens shape is preferable since welding of the sheet bond portions <NUM> is stabilized, and the concave lens shape is preferable in that an area may be further reduced.

It is possible to appropriately determine the area rate of the sheet bond portions <NUM> and the area of each of the sheet bond portions <NUM> in the non-stretchable region. However, in general, ranges below are preferable since the area of each of the sheet bond portions <NUM> is small, the area rate of the sheet bond portions <NUM> is low, and thus the non-stretchable region <NUM> is not hardened.

Area rate of sheet bond portions <NUM> : <NUM> to <NUM>% (particularly <NUM> to <NUM>%).

As described above, the elongation at the elastic limit of the non-stretchable region <NUM> may be changed by the arrangement pattern of the through holes <NUM>, dimensions of each of the through holes <NUM>, and the center interval of the through holes <NUM>. Therefore, although not illustrated, it is possible to make the elongation at the elastic limit different between a plurality of positions in the stretchable region <NUM> or a plurality of non-stretchable regions <NUM>. For example, in a preferable mode, the elongation at the elastic limit in the non-stretchable region <NUM> of the front body F is set to be larger than the elongation at the elastic limit in the non-stretchable region <NUM> of the back body B.

Even though the non-stretchable region <NUM> has a section that linearly continues along the width direction similarly to the stretchable region, since the area rate of the sheet bond portions in the non-stretchable region <NUM> is higher than that in the stretchable region, the elongation at the elastic limit is remarkably low in the non-stretchable region <NUM>. Specifically, it is possible to adopt another mode for eliminating elasticity such as a mode in which the elongation at the elastic limit is <NUM>% or less, a mode in which cutting is performed in the width direction at one position or a plurality of positions as in a conventional stretchable structure using a rubber thread, etc..

Characteristically, as illustrated in <FIG>, <FIG>, <FIG> and <FIG>, in the first sheet layer 20A and the second sheet layer 20B of the stretchable region <NUM>, the vent hole <NUM> is formed by piercing to penetrate the sheet layer in a thickness direction in a portion other than the sheet bond portions <NUM>. As a result, it is possible to improve air permeability in the thickness direction, without impairing a texture, due to the presence of the through holes <NUM> of the elastic film <NUM> and the vent hole <NUM> in at least one of the first sheet layer 20A and the second sheet layer 20B. The vent hole <NUM> may be formed in only either one of the first sheet layer 20A and the second sheet layer 20B. In addition, as illustrated in <FIG>, <FIG>, and <FIG>, the vent hole <NUM> may be formed in the non-stretchable region <NUM> and the vent hole may be or may not be formed in the stretchable region <NUM>.

The vent hole <NUM> may be formed by a punching process or a needle prick process. The vent hole <NUM> may be processed before the sheet bond portions <NUM> are formed, that is, in a single state of the first sheet layer 20A and the second sheet layer 20B, or may be processed in a state in which the first sheet layer 20A, the elastic film <NUM>, and the second sheet layer 20B are stacked after the sheet bond portions <NUM> are formed. However, since the elastic film <NUM> is present after the sheet bond portions <NUM> are formed, it is desirable that the vent hole <NUM> is formed by piercing at a position overlapping the through holes <NUM> of the elastic film <NUM> as described below. The elastic film <NUM> maybe pierced together with the first sheet layer 20A, the elastic film <NUM>, and the second sheet layer 20B while they are stacked. However, in this case, stretching stress due to the piercing, an influence on the elongation at the elastic limit, cutting of the elastic film <NUM>, etc. need to be taken into consideration.

A formation position of the vent hole <NUM> is not particularly restricted. However, the through holes <NUM> formed in the elastic film <NUM> are enlarged to both sides of the sheet bond portions <NUM> in the width direction when the stretchable region <NUM> is stretched at the time of use, and the through holes <NUM> are enlarged to both sides of the sheet bond portions <NUM> in the width direction even in the natural length state in the non-stretchable region <NUM>. Thus, as in the illustrated mode, in any one of the stretchable region <NUM> and the non-stretchable region <NUM>, at least one vent hole <NUM> is formed on each side of each of the sheet bond portions <NUM> in the stretching and contracting direction in terms of improving air permeability.

In particular, in a preferable mode, in a state in which the stretchable region <NUM> is stretched, that is, in a state in which an elastic limit is included excluding the natural length state, the vent hole <NUM> is disposed with respect to the through holes <NUM> such that a part or a whole of the vent hole <NUM> overlaps each of the through holes <NUM>, as illustrated in <FIG> and <FIG>, which are not according to the invention. When the stretchable region <NUM> is stretched at the time of use, since the through hole <NUM> formed in the elastic film <NUM> is enlarged in the width direction, in a case in which the vent hole <NUM> is disposed with respect to the through holes <NUM> such that a part or a whole of the vent hole <NUM> overlaps each of the enlarged through holes <NUM>, air permeability via the through hole <NUM> is particularly improved. <FIG> and <FIG> illustrate overlapping states at the elastic limit, and overlap begins in a process of stretching to the elastic limit. Therefore, it is preferable to adopt a configuration in which the vent hole <NUM> of the first sheet layer 20A and the second sheet layer 20B overlaps each of the through holes <NUM> of the elastic film <NUM> in a stretch rate range of <NUM> to <NUM>% on the assumption of the worn state.

For a similar reason, when the vent hole <NUM> is formed in the non-stretchable region <NUM> as illustrated in <FIG>, which is not according to the invention, <FIG>, which is not according to the invention, and <FIG>, which is not according to the invention, it is preferable to dispose the vent hole <NUM> with respect to the through hole <NUM> such that a part or a whole of the vent hole <NUM> overlaps the through hole <NUM> in the natural length state of the non-stretchable region. In a preferable mode, one vent hole is preferable disposed to straddle and overlap a plurality of through holes as illustrated in <FIG>. The mode illustrated in <FIG>, which is not according to the invention, relates to the non-stretchable region <NUM>. However, the same mode may be adopted in the stretchable region <NUM>.

In the stretchable region <NUM> and the non-stretchable region <NUM>, when a part or a whole of the vent hole <NUM> is disposed to overlap the through hole <NUM> during use, there is a concern that a skin exposure may increase due to improvement of permeability, or leak prevention may deteriorate even though air permeability is improved. Therefore, to solve such problem, although not illustrated, it is preferable, independently of a state in which the stretchable region <NUM> is stretched or not, none of the vent hole <NUM> overlaps the through holes <NUM>.

The first sheet layer 20A and the second sheet layer 20B are layers that cover the elastic film <NUM>, and are members that require durability such as rub resistance. In addition, when the first sheet layer 20A is composed of a nonwoven fabric and the second sheet layer 20B is composed of a nonwoven fabric, the number of vent holes <NUM> may not be excessively increased since the material has air permeability. On the other hand, a considerable number of through holes <NUM> of the elastic film <NUM> are used to ensure air permeability and join uniformly the first sheet layer 20A and the second sheet layer 20B as one unit. Therefore, in a preferable mode, the number of vent holes <NUM> is set to be smaller than the number of through holes <NUM>. The modes illustrated in <FIG> and <FIG>, which are not according to the invention, relate to the non-stretchable region <NUM>. However, the same modes may be adopted in the stretchable region <NUM>.

A shape of the vent hole <NUM> is not particularly restricted, and may be set to an arbitrary shape such as a perfect circle (illustrated mode), an ellipse, a polygon such as a triangle, a rectangle, a rhombus, etc., a star shape, a cloud shape, etc. A size of the vent hole <NUM> is not particularly restricted. However, when the size is excessively small or an excessively small number of vent holes <NUM> are present, an effect of improving air permeability becomes poor. When the size is excessively large or an excessively large number of vent holes <NUM> are present, a decrease in strength or deterioration in appearance of the first sheet layer 20A and the second sheet layer 20B is caused. Thus, in general, an area of the vent hole <NUM> is preferably set to about <NUM> to <NUM><NUM>, and an area rate of the vent holes <NUM> is preferably set to about <NUM> to <NUM>%.

A planar array of the vent holes <NUM> may be appropriately determined. However, as illustrated in <FIG>, which is not according to the invention, <FIG>, which is not according to the invention, <FIG>, which is not according to the invention, <FIG>, which is not according to the invention, and <FIG>, which is not according to the invention, it is preferable to adopt a planar array in which the vent holes <NUM> are regularly repeated. Similarly to the arrangement mode of the sheet bond portions <NUM> illustrated in <FIG>, in addition to the planar array in which the vent holes <NUM> are regularly repeated such as an oblique lattice shape or a hexagonal lattice shape (these shapes are also referred to as a staggered shape), a square lattice shape, a rectangular lattice shape, a parallel body lattice shape (a mode in which two groups are provided such that a large number of parallel oblique row groups intersect each other as illustrated in the figure), etc. (including a mode in which these shapes are inclined at an angle less than <NUM> degrees with respect to the width direction), it is possible to adopt a planar array in which a group of the vent holes <NUM> (arrangement of a group unit may be regular or irregular, and a pattern, a letter shape, etc. may be used) is regularly repeated.

A part or a whole of the mode for solving the first problem may be applied to the mode for solving the second problem. On the contrary, a part or a whole of the mode for solving the second problem may be applied to the mode for solving the first problem.

The terms used in the specification have the following meanings unless otherwise stated.

Claim 1:
An absorbent article comprising
a stretchable region (<NUM>) stretchable at least in one direction, wherein
the stretchable region is formed by stacking an elastic film (<NUM>) between a first sheet layer (20A) composed of a nonwoven fabric and a second sheet layer (20B) composed of a nonwoven fabric, and in a state in which the elastic film is stretched in a stretching and contracting direction of the stretchable region, the first sheet layer and the second sheet layer are joined via through holes (<NUM>) formed in the elastic film at a large number of sheet bond portions (<NUM>) arranged at intervals in each of a stretching and contracting direction and a direction orthogonal thereto,
each of the through holes (<NUM>) should have an opening area larger than an area of the corresponding sheet bond portion (<NUM>) such that the sheet bond portions (<NUM>) are formed within the through holes (<NUM>),
fibers of the first sheet layer and the second sheet layer continuing from around the sheet bond portions are left in the sheet bond portions, and
in the sheet bond portions, the first sheet layer and the second sheet layer are joined at least by a melted and solidified material of the elastic film which has infiltrated and solidified among the first sheet layer and the second sheet layer.