Absorbent article

Abstract

An absorbent article (1) includes a liquid-absorbent absorbent core (11) and a sheet member (25) provided on the skin side or the non-skin side of the absorbent core (11). The sheet member (25) has a nonwoven fabric layer (25a) comprising a plurality of non-thermally bonded fibers (25as). The nonwoven fabric layer (25a) has a surface exposed to the skin side or the non-skin side. The fibers of the nonwoven fabric layer (25a) have an average fiber length of 12 mm or less. The maximum value (hf) of fluff height of the fibers of the nonwoven fabric layer after a fluff height measurement test on the nonwoven fabric layer (25a) is less than the value (hn) obtained by subtracting the maximum value (hf) of the fluff height of the fibers of the nonwoven fabric layer (25a) from the average fiber length (hs) of the fibers of the nonwoven fabric layer (25a).

Description

Absorbent Article

[0001] The present invention relates to an absorbent article.

[0002] A sheet member used for an absorbent article is a member that comes into contact with the wearer's skin and absorbs excrement, sweat, and the like. For example, Patent Document 1 discloses a disposable diaper including a sweat-absorbent sheet. In the diaper of Patent Document 1, the sweat-absorbent sheet is provided so as to be in contact with the waist circumference of the wearer to absorb the wearer's sweat.

[0003] Japanese Unexamined Patent Publication No. 2001-327534

[0004] In a sheet member such as that described in Patent Document 1, if fuzzing occurs on the surface, when the sheet member comes into contact with the wearer's skin, friction may cause a sense of discomfort to the wearer or deteriorate the texture of the product. In particular, sheet members using cotton fibers are prone to fuzzing, which has been a problematic issue in some cases. Additionally, when an absorbent article such as a diaper including the sheet member is worn for a long period of time, the surface of the sheet member may rub against the wearer's skin or clothing, which may increase the degree of fuzzing. In such cases, this may increase the wearer's discomfort, or the fluffing may cause fibers to fall out from the surface, which may reduce the durability of the sheet member itself.

[0005] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an absorbent article using a sheet member that is less prone to fuzzing and has high durability.

[0006] The main invention for achieving the above object is an absorbent article including a liquid-absorbent absorbent core, and a sheet member provided on the skin side or non-skin side of the absorbent core, wherein the sheet member has a nonwoven fabric layer including a plurality of non-heat-fusible fibers, the nonwoven fabric layer has a surface exposed to the skin side or the non-skin side, the average fiber length of the fibers of the nonwoven fabric layer is 12 mm or less, and the maximum value of the fuzz height of the fibers of the nonwoven fabric layer after a fuzz height measurement test performed on the nonwoven fabric layer is shorter than a value obtained by subtracting the maximum value of the fuzz height of the fibers of the nonwoven fabric layer from the average fiber length of the fibers of the nonwoven fabric layer. Other features of the present invention will be clarified by the description in the present specification and the accompanying drawings.

[0007] According to the present invention, it is possible to provide an absorbent article using a sheet material that is less prone to pilling and has high durability.

[0008] Figure 1 is a schematic perspective view of diaper 1 from the ventral side. Figure 2 is a schematic plan view of diaper 1 in its unfolded and extended state, as seen from the wearer's skin side. Figure 3 is a schematic cross-sectional view of A-A in Figure 2. Figure 4 is a schematic cross-sectional view of the sheet portion 25. Figure 5A is an enlarged view of the sheet portion 25 as seen from the skin side. Figure 5B is an enlarged schematic view of a part of Figure 5A. Figure 6A is data showing the distribution of fiber lengths of skin-side fibers constituting the nonwoven fabric layer 25a (skin-side layer 25a) in this embodiment, and Figure 6B is data showing the distribution of fiber lengths of skin-side fibers in the sheet member of the comparative example. Figure 7A is a graph showing the fiber length distribution of Figure 6A (this embodiment), and Figure 7B is a graph showing the fiber length distribution of Figure 6B (comparative example). Figures 8A to 8D are diagrams illustrating the test method for the fluff height measurement test. Figures 9A and 9B are enlarged views of the area X of the sheet member after the test, as captured in Figure 8D. This is a magnified photograph of the cross-sectional structure of the skin-side layer 25a (nonwoven fabric layer 25a) and the non-skin-side layer 25b (other layer 25b) of the sheet portion 25. Figures 11A and 11B illustrate a modified example 1 of the arrangement of the sheet portion 25. This is a diagram illustrating a modified example 2 of the arrangement of the sheet portion 25. This is a diagram illustrating a modified example 3 of the arrangement of the sheet portion 25. This is a diagram illustrating a modified example 4 of the arrangement of the sheet portion 25.

[0009] The following matters will become clear from the description in this specification and the accompanying drawings: (Aspect 1) An absorbent article having a liquid-absorbing absorbent core and a sheet member provided on the skin side or non-skin side of the absorbent core, wherein the sheet member has a nonwoven fabric layer having a plurality of non-heat-fusible fibers, the nonwoven fabric layer has a surface exposed on the skin side or non-skin side, the average fiber length of the fibers in the nonwoven fabric layer is 12 mm or less, and the maximum value of the fluff height of the fibers in the nonwoven fabric layer after a fluff height measurement test is shorter than the value obtained by subtracting the maximum value of the fluff height of the fibers in the nonwoven fabric layer from the average fiber length of the fibers in the nonwoven fabric layer.

[0010] In the absorbent article of Embodiment 1, compared to the case where the average fiber length is greater than 12 mm, the fiber density tends to increase and the inter-fiber distance tends to decrease. As a result, fibers tend to intertwine more easily within the nonwoven fabric layer, making it less likely for fuzzing to occur and for fibers to fall out. Furthermore, even if fuzzing occurs, the length of the fuzzed portion is shorter than the length of the non-fuzzed portion, so a large frictional force is less likely to act on the fuzzed portion, and even if the fuzzed portion is pulled, the non-fuzzed portion can more easily resist the tensile force. This makes it possible to realize an absorbent article that is less prone to fuzzing and has high durability.

[0011] (Aspect 2) An absorbent article according to aspect 1, characterized in that, in an unfolded and stretched state, it has a longitudinal direction, a left-right direction and a thickness direction which are mutually orthogonal to each other, the sheet member has other layers at different positions in the thickness direction, the other layers comprise heat-fusible fibers whose average fiber length is longer than the fibers of the nonwoven fabric layer, the non-heat-fusible fibers and the heat-fusible fibers have intertwined portions, 90% by weight or more of the fibers constituting the nonwoven fabric layer are the non-heat-fusible fibers, and 90% by weight or more of the fibers constituting the other layers are the heat-fusible fibers.

[0012] According to the absorbent article of embodiment 2, the probability of entanglement between the fibers in the nonwoven fabric layer and the heat-fusible fibers, which have a longer average fiber length than the said fibers, becomes higher. Therefore, even if fuzzing occurs in the fibers of the nonwoven fabric layer, the fibers are more likely to fall out of the nonwoven fabric layer because they are intertwined with the heat-fusible fibers of other layers. This makes it easier to improve the durability of the sheet member (absorbent article).

[0013] (Aspect 3) An absorbent article according to aspect 1 or 2, characterized in that, of the other layers, at least a portion of the fibers of the nonwoven fabric layer are present on the surface facing the nonwoven fabric layer in the thickness direction.

[0014] According to the absorbent article of embodiment 3, at least a portion of the fibers in the nonwoven fabric layer penetrate to other layers, increasing the probability of them becoming entangled with heat-fused fibers in those other layers. This makes it easier to suppress the shedding of fibers from the nonwoven fabric layer, thereby improving the durability of the sheet member (absorbent article).

[0015] (Aspect 4) An absorbent article according to any one of aspects 1 to 3, characterized in that an adhesive is provided on the opposing surface of the other layer.

[0016] According to the absorbent article of embodiment 4, the fibers that penetrate from the nonwoven fabric layer to other layers are more easily fixed more firmly by the adhesive. As a result, the fibers in the nonwoven fabric layer are less likely to fall out, and the durability of the sheet member (absorbent article) can be further improved.

[0017] (Aspect 5) An absorbent article according to any one of aspects 1 to 4, characterized in that, in the sheet member before the fluffing height measurement test, the number of fibers per unit area of ​​the nonwoven fabric layer that protrude from the exposed side of the nonwoven fabric layer is greater than the number of fibers per unit area of ​​the nonwoven fabric layer that protrude from the side of the nonwoven fabric layer facing the other layer.

[0018] According to the absorbent article of embodiment 5, the fewer the number of fibers protruding from the nonwoven fabric layer toward the exposed side, the less likely fuzzing is to occur. Conversely, the more fibers protruding from the nonwoven fabric layer toward the side facing other layers, the higher the probability of entanglement with fibers in other layers, making it less likely for fibers to fall out. Therefore, it is possible to make the sheet member (absorbent article) less prone to fuzzing and less likely for fibers to fall out.

[0019] (Aspect 6) The other layer is an absorbent article according to any one of aspects 1 to 5, characterized in that it has portions in which the heat-fusible fibers are fused together.

[0020] According to the absorbent article of embodiment 6, the rigidity of the sheet itself is increased because there are portions in other layers where heat-fusible fibers are fused together. Furthermore, when fibers from the nonwoven fabric layer penetrate to other layers, these penetrating fibers are more easily held in place by the heat-fusible fibers that are scattered and joined in the other layers, making it less likely for the fibers to fall out. This improves the durability of the sheet member (absorbent article).

[0021] (Aspect 7) The nonwoven fabric layer has a predetermined basis weight portion having fibers of the nonwoven fabric layer with a predetermined basis weight, and a low basis weight portion having fibers of the nonwoven fabric layer with a lower basis weight than the predetermined basis weight portion, wherein the predetermined basis weight portion and the low basis weight portion are arranged alternately in the longitudinal direction, and the predetermined basis weight portion and the low basis weight portion are arranged alternately in the left-right direction, making it an absorbent article according to any one of aspects 1 to 6.

[0022] According to the absorbent article of embodiment 7, by having low-basis-weight portions dispersed on the surface of the sheet member, the portion of the nonwoven fabric layer that comes into contact with the wearer's skin or clothing can be reduced compared to the case where there are no low-basis-weight portions. This suppresses the large frictional force acting on the surface of the nonwoven fabric layer and reduces the possibility of fibers falling out of the nonwoven fabric layer. Therefore, the durability of the sheet member (absorbent article) can be improved.

[0023] (Aspect 8) An absorbent article according to any one of aspects 1 to 7, characterized in that the average fiber length of the fibers in the nonwoven fabric layer is longer than the maximum thickness of the sheet member before the fluffing height measurement test.

[0024] According to the absorbent article of embodiment 8, the fibers of the nonwoven fabric layer are more likely to penetrate to other layers, increasing the probability of entanglement with the fibers of other layers. Therefore, compared to the case where the average fiber length of the fibers of the sheet member is less than or equal to the maximum thickness of the sheet member, the risk of fibers falling out of the sheet member is reduced, and the durability of the sheet member (absorbent article) can be improved.

[0025] (Aspect 9) The sheet member is an absorbent article according to any one of aspects 1 to 8, characterized in that it is provided on the skin side of the absorbent core and covers the entire area of ​​the absorbent core.

[0026] According to the absorbent article of embodiment 9, the risk of fibers shedding during wear is reduced in the top sheet of the absorbent body, and durability is improved. This makes it easier to suppress discomfort and a decrease in liquid absorbency when wearing the absorbent article.

[0027] (Aspect 10) An absorbent article according to any of aspects 1 to 9, characterized in that, in an unfolded and extended state, it has a longitudinal direction, a left-right direction and a thickness direction which are mutually orthogonal, and has an expandable / contractable member that can be expanded or contracted in at least one of the longitudinal direction or the left-right direction, and when viewed in the thickness direction, the sheet member has a portion that overlaps with the expandable / contractable member.

[0028] According to the absorbent article of embodiment 10, in the portion where the expandable member is provided, wrinkles are more likely to form on the surface of the sheet member due to the contraction of the expandable member, thereby reducing the portion of the sheet member that comes into contact with the wearer's skin or clothing. This reduces the risk of the fibers of the nonwoven fabric layer falling out of the sheet member, thereby improving the durability of the sheet member (absorbent article).

[0029] (Aspect 11) An absorbent article according to any one of aspects 1 to 10, characterized in that the basis weight of the non-heat-fusible fibers in the nonwoven fabric layer is greater than the basis weight of the fibers in the nonwoven fabric layer other than the non-heat-fusible fibers.

[0030] According to the absorbent article of embodiment 11, the amount of fiber fusion in the nonwoven fabric layer can be reduced compared to when the basis weight of fibers other than non-heat-fusible fibers is greater than that of non-heat-fusible fibers. In this case, the flexibility of the sheet member can be increased, making it easier to improve the feel of the sheet member (absorbent article) against the skin.

[0031] (Aspect 12) An absorbent article according to any one of aspects 1 to 11, characterized in that the maximum value of the fluff height of the fibers of the nonwoven fabric layer after the fluff height measurement test is three times or less the maximum value of the fluff height of the fibers of the nonwoven fabric layer before the fluff height measurement test.

[0032] According to the absorbent article of embodiment 12, the length of the portion of the fibers protruding from the nonwoven fabric layer can be shortened compared to when the maximum value of the fiber fluff height of the nonwoven fabric layer after the fluff height measurement test is greater than three times the maximum value of the fiber fluff height of the nonwoven fabric layer before the fluff height measurement test. As a result, the fibers are less likely to come out of the nonwoven fabric layer, and the durability of the sheet member (absorbent article) can be improved.

[0033] (Aspect 13) An absorbent article according to any one of aspects 1 to 12, characterized in that the maximum value of the fluff height of the fibers of the nonwoven fabric layer after the fluff height measurement test is 1 / 4 or less of the average fiber length of the fibers of the nonwoven fabric layer.

[0034] According to the absorbent article of embodiment 13, compared to the case where the maximum fluffing height of the fibers is greater than 1 / 4 of the average fiber length of the fibers in the nonwoven fabric layer, the fibers are less likely to come out of the nonwoven fabric layer, and the durability of the sheet member (absorbent article) can be improved.

[0035] ===Embodiment=== In the following description of the sheet member for absorbent articles according to this embodiment, an adult pant-type disposable diaper 1 (hereinafter also simply referred to as "diaper 1") will be used as an example of an absorbent article, and a sweat-absorbing sheet (sheet portion 25, 35) for the waist portion 20, 30 of diaper 1 will be used as an example of a sheet member. However, the absorbent article according to this embodiment is not limited to the above, and can also be applied to, for example, pant-type disposable diapers for infants, shorts-type sanitary napkins, tape-type disposable diapers, etc. Furthermore, the sheet member can be any member that can come into contact with the skin side of each absorbent article, regardless of whether it is a sweat-absorbing sheet.

[0036] <Basic Structure of the Pants-Type Disposable Diaper 1> Figure 1 is a schematic perspective view of diaper 1 as seen from the ventral side. Figure 2 is a schematic plan view of diaper 1 in its unfolded and extended state as seen from the wearer's skin side. Figure 3 is a schematic cross-sectional view of A-A in Figure 2.

[0037] The "unfolded state" of diaper 1 refers to the state in which the diaper 1, in the pant-type state shown in Figure 1, is unfastened by releasing the side joints SS (described later) on both sides in the left-right direction, thereby separating the ventral waist portion 20 (described later) and the dorsal waist portion 30 (described later), and opening the diaper 1 vertically, thereby unfolding the diaper 1 onto a flat surface. The "stretched state" of diaper 1 refers to the state in which the product (diaper 1) is stretched without wrinkles, specifically, the state in which the dimensions of each component constituting the diaper 1 (for example, the absorbent body 10 and the ventral waist portion 20, etc.) are stretched to match or be close to the dimensions of the individual component.

[0038] Diaper 1, in its pant-type state when worn as shown in Figure 1, has intersecting vertical, horizontal, and front-to-back directions, and has a waist opening BH and a pair of leg openings LH. In the vertical direction, the waist opening BH side is the upper side, and the side that is the wearer's crotch side is the lower side. In the front-to-back direction, the side that is the wearer's abdominal side is the front side, and the side that is the wearer's back side is the back side. Furthermore, in the unfolded and extended state shown in Figure 2, diaper 1 has three mutually orthogonal directions: a longitudinal direction, a horizontal direction, and a thickness direction (the direction that penetrates the paper in Figure 2). The longitudinal direction is along the aforementioned vertical direction. One side of the longitudinal direction corresponds to the abdominal side (front side), and the other side corresponds to the back side (back side). Furthermore, as shown in Figure 3, diaper 1 has a thickness direction in which the materials are layered, and in the thickness direction, the side that comes into contact with the wearer is the skin side, and the opposite side is the non-skin side.

[0039] Diaper 1 comprises an absorbent body 10 and an outer casing 18. The outer casing 18 has a pair of waist sections 20 and 30 and a crotch section 40 located between the wearer's legs. The outer casing 18 is attached to the non-skin side of the absorbent body 10 with an adhesive or the like. Of the pair of waist sections 20 and 30, the one located on the wearer's ventral (front) side is also called the ventral waist section 20, and the one located on the dorsal (rear) side is also called the dorsal waist section 30. The ventral waist section 20 and the dorsal waist section 30 are joined on both sides in the left-right direction by a pair of side joints SS. Examples of joining methods using the side joints SS include heat welding, ultrasonic welding, and joining with adhesive.

[0040] As shown in Figure 3, the absorbent body 10 includes an absorbent core (absorbent material) 11, a liquid-permeable top sheet 12 positioned on the skin side of the absorbent core 11, a liquid-impermeable back sheet 13 positioned on the non-skin side of the absorbent core 11, and an outer sheet 14. The absorbent core 11 can be any material that absorbs and retains excretory fluid, and examples include liquid-absorbent materials such as pulp fibers or superabsorbent polymers (SAP) molded into a predetermined shape. The absorbent core 11 may also be covered with a liquid-permeable sheet such as tissue paper or nonwoven fabric. The top sheet 12 is formed from a nonwoven fabric such as air-through nonwoven fabric or spunbond nonwoven fabric. The back sheet 13 is a liquid-impermeable and breathable film such as polyethylene or polypropylene. The outer sheet 14 is formed from a nonwoven fabric equivalent to that of the top sheet 12.

[0041] As shown in Figure 2, multiple leg-circumference elastic members 15 (e.g., elastic threads) that expand and contract along the longitudinal direction of the absorbent body 10 are provided on both sides of the absorbent body 10 in the left-right direction. Furthermore, a leak-proof wall portion that can stand upright on the skin side may be provided by, for example, providing an elastic member that expands and contracts in the longitudinal direction inward from the leg-circumference elastic members 15 in the left-right direction.

[0042] As shown in Figures 2 and 3, the outer casing 18 has an inner layer sheet 21, a ventral outer layer sheet 22 (outer layer sheet), and a dorsal outer layer sheet 32 ​​(outer layer sheet).

[0043] The inner layer sheet 21 is positioned from the ventral waist area 20 through the crotch area 40 to the dorsal waist area 30 (Figure 3). The width (length in the left-right direction) of the inner layer sheet 21 in the ventral waist area 20 and the dorsal waist area 30 is greater than the width (length in the left-right direction) of the inner layer sheet 21 in the crotch area 40 (Figure 2). As the inner layer sheet 21, air-through nonwoven fabric, spunbond nonwoven fabric, SMS nonwoven fabric (spunbond-meltblown-spunbond nonwoven fabric), waterproof film, etc. can be used.

[0044] As shown in FIGS. 2 and 3, the ventral outer layer sheet 22 is provided on the non-skin side relative to the inner layer sheet 21, and the ventral outer layer sheet 22 and the inner layer sheet 21 constitute the ventral waist circumference portion 20. The outer end (upper end) of the ventral outer layer sheet 22 in the longitudinal direction is folded back toward the skin side. The folded-back portion 22r of the ventral outer layer sheet 22 wraps around one end (outer end) of the inner layer sheet 21 in the longitudinal direction. Note that the outer end (upper end) of the ventral outer layer sheet 22 in the longitudinal direction may have a configuration that is not folded back.

[0045] Similarly, as shown in FIGS. 2 and 3, the dorsal outer layer sheet 32 is provided on the non-skin side relative to the inner layer sheet 21, and the dorsal outer layer sheet 32 and the inner layer sheet 21 constitute the dorsal waist circumference portion 30. The outer end (upper end) of the dorsal outer layer sheet 32 in the longitudinal direction is folded back toward the skin side. The folded-back portion 32r of the dorsal outer layer sheet 32 wraps around the other end (outer end) of the inner layer sheet 21 in the longitudinal direction. Note that the outer end (upper end) of the dorsal outer layer sheet 32 in the longitudinal direction may have a configuration that is not folded back.

[0046] As the ventral outer layer sheet 22 and the dorsal outer layer sheet 32, air-through nonwoven fabric, spunbond nonwoven fabric, SMS nonwoven fabric (spunbond-meltblown-spunbond nonwoven fabric) and the like can be used.

[0047] The ventral waist circumference portion 20 and the dorsal waist circumference portion 30 each have waist circumference elastic members 23 and 33 that are extendable and contractible in the left-right direction. The plurality of waist circumference elastic members 23 and 33 are arranged at intervals in the vertical direction between the inner layer sheet 21 and the ventral outer layer sheet 22, and between the inner layer sheet 21 and the dorsal outer layer sheet 32, and are fixed in an extended state in the left-right direction (see FIGS. 2 and 3). Accordingly, the ventral waist circumference portion 20 and the dorsal waist circumference portion 30 extend and contract in the left-right direction to fit around the wearer's waist. Note that examples of the waist circumference elastic members 23 and 33 include thread-like elastic members such as thread rubber, and elongated elastic sheets.

[0048] Further, in the present embodiment, in the dorsal waist portion 30, a rear leg-surrounding elastic member 34 is provided between the inner layer sheet 21 and the dorsal outer layer sheet 32. The rear leg-surrounding elastic member 34 may be, for example, a plurality of thread rubbers, a belt-shaped elastic sheet having stretchability, or the like. The rear leg-surrounding elastic member 34 is bonded and fixed in an extended state by an adhesive such as a hot-melt adhesive.

[0049] Further, in the present embodiment, sheet portions 25 and 35 that easily absorb the wearer's sweat are provided in a predetermined region on the most skin-facing side among the ventral waist portion 20 and the dorsal waist portion 30 (hatched portions in FIG. 2). The sheet portions 25 and 35 are disposed closer to the skin side than the absorbent main body 10 (absorbent core 11), have a shorter length in the up-down direction than the inner layer sheet 21, the ventral outer layer sheet 22, the dorsal outer layer sheet 32, and the like, and are belt-shaped sheet members disposed so as to cover the longitudinal ends of the absorbent main body 10. Details of the sheet portions 25 and 35 will be described later.

[0050] The basic configuration of the diaper 1 has been described above, but the configuration of the diaper 1 described above is an example and is not limited thereto. For example, the diaper 1 of the present embodiment has a configuration including an exterior body 18 having three parts: the ventral waist portion 20, the dorsal waist portion 30, and the crotch portion 40 connecting these, but the configuration is not limited thereto. For example, the diaper may have a configuration in which the ventral waist portion 20 and the dorsal waist portion 30 are formed as separate members, and the non-skin side surface of the absorbent main body 10 is exposed at the crotch portion, or may have an exterior member formed of a single continuous member extending from the ventral waist portion 20 to the dorsal waist portion 30.

[0051] <Regarding Sheet Portions 25 and 35> Hereinafter, specific configurations of the sheet portions 25 and 35 according to the present embodiment will be described. In the present embodiment, the sheet portion 25 provided in the ventral waist portion 20 and the sheet portion 35 provided in the dorsal waist portion 30 have substantially the same configuration. Therefore, in the following description, regarding the content common to both the sheet portion 25 and the sheet portion 35, only the sheet portion 25 will be described as a representative of both. For the sheet portion 35, reference numerals for members corresponding to those of the sheet portion 25 will be indicated in parentheses as necessary, and specific description will be omitted.

[0052] Figure 4 is a schematic cross-sectional view of the sheet portion 25. Figure 5A is an enlarged view of the sheet portion 25 as seen from the skin side. Figure 5B is an enlarged schematic view of a part of Figure 5A. As described above, in this embodiment, the sheet portion 25 constitutes a part of the surface of the abdominal torso portion 20 that comes into contact with the wearer's skin (see Figure 3). As shown in Figure 4, the sheet portion 25 has a skin-side layer 25a that is positioned to come into contact with the wearer's skin, and a non-skin-side layer 25b that is located on the non-skin side in the thickness direction of the skin-side layer 25a.

[0053] The skin-side layer 25a is a nonwoven fabric layer with a base fiber made of non-heat-fusible fibers such as cotton fibers. Cotton fibers are soft, have a rounded fiber shape, and are highly absorbent. Therefore, by using cotton fibers as the base fiber of the skin-side layer 25a that comes into contact with the wearer's skin, it is possible to provide a comfortable feel against the wearer's skin and reduce irritation to the wearer's skin during wear. The term "base fiber" as used above means a material that accounts for more than 50% of the mass (weight %) of each layer (skin-side layer 25a, non-skin-side layer 25b).

[0054] As the base fibers for the non-skin-facing layer 25b, heat-fusible fibers such as polyester fibers, polypropylene fibers, polyethylene fibers, and polyurethane fibers, or composite fibers thereof, can be used. In the following, the base fibers of the skin-facing layer 25a will also be referred to as "skin-facing fibers," and the base fibers of the non-skin-facing layer 25b will also be referred to as "non-skin-facing fibers." Furthermore, the skin-facing layer 25a will also be referred to as "nonwoven fabric layer 25a," and the non-skin-facing layer 25b will also be referred to as "other layer 25b."

[0055] Furthermore, while the aforementioned fibers may be either those with a hydrophilic treatment applied to their surface or those without, it is preferable that at least the fiber on the skin side has hydrophilic properties.

[0056] Furthermore, in the sheet portion 25 (sheet member) of this embodiment, the skin-side fibers (cotton fibers) 25as, which are the base fibers of the skin-side layer 25a, have portions that are entangled with the non-skin-side fibers 25bs, which are the base fibers of the non-skin-side layer 25b (see Figure 4). As a method for integrating the skin-side layer 25a and the non-skin-side layer 25b by entanglement, a known water flow entanglement method, such as a water jet, can be used.

[0057] Furthermore, the skin-side layer 25a has a predetermined basis weight portion 25aP with skin-side fibers 25as of a predetermined basis weight, and a low basis weight portion 25aL in which the basis weight of the skin-side fibers 25as is lower than that of the predetermined basis weight portion 25aP. As shown in Figures 4 and 5, when the sheet portion 25 is viewed in the thickness direction, it has a portion where the predetermined basis weight portion 25aP and the non-skin-side layer 25b overlap, and a portion where the low basis weight portion 25aL and the non-skin-side layer 25b overlap. By having a portion where the predetermined basis weight portion 25aP and the non-skin-side layer 25b of the skin-side layer 25a overlap, when worn, the predetermined basis weight portion 25aP of the sheet portion 25 comes into contact with the wearer's skin, improving the water absorption and feel of the sheet portion 25 (diaper 1) when worn. On the other hand, having an overlapping portion between the low basis weight section 25aL and the non-skin layer 25b allows the overlapping portion between the predetermined basis weight section 25aP and the non-skin layer 25b to absorb moisture such as sweat from the wearer's skin when worn. This facilitates evaporation of the moisture absorbed by the predetermined basis weight section 25aP from the low basis weight section 25aL, where the basis weight of the skin-side fibers 25as is lower, and also facilitates the movement of moisture from the low basis weight section 25aL to the non-skin layer 25b.

[0058] The "low basis weight portion 25aL" is any portion where the basis weight of the skin-side fibers 25as is lower than that of the predetermined basis weight portion 25aP, and includes cases where skin-side fibers 25as are provided in the low basis weight portion 25aL and cases where skin-side fibers 25as are not provided. In either case, it is preferable that the low basis weight portion 25aL is a portion that is recessed on the non-skin side than the predetermined basis weight portion 25aP (see Figure 4). Because the low basis weight portion 25aL is recessed on the non-skin side than the predetermined basis weight portion 25aP, when worn, the predetermined basis weight portion 25aP of the skin-side layer 25a of the sheet portion 25 is a portion that is more likely to come into contact with the wearer's skin, improving the feel against the wearer's skin, while the low basis weight portion 25aL is a portion that is less likely to come into contact with the wearer's skin. Therefore, moisture such as sweat can be easily transferred to the non-skin layer 25b via the low basis weight portion 25aL where the skin-side fibers 25as are less numerous. Even when the skin-side layer 25a absorbs moisture such as sweat during wear, the portion of the skin-side layer 25a that comes into contact with the wearer's skin is reduced, thereby reducing the risk of the wearer feeling sticky on their skin even when the skin-side fibers 25as of the skin-side layer 25a absorb moisture.

[0059] In this embodiment, the low basis weight portion 25aL is a portion where there are almost no skin-side fibers 25as, and the basis weight of the skin-side fibers 25as is 0 (zero). Simply put, it is a portion where the skin-side layer 25a is missing in the thickness direction. Therefore, when the sheet portion 25 is viewed from the skin side, the non-skin-side layer 25b (non-skin-side fibers 25bs) can be seen through the low basis weight portion 25aL (see Figure 5A). Note that since the skin-side fibers 25as are soft fibers with some fluidity, a portion where the basis weight of the skin-side fibers 25as is 0 (zero) does not mean that there are absolutely no skin-side fibers 25as, but rather that there may be a portion in the low basis weight portion 25aL where a few skin-side fibers 25as are provided.

[0060] Furthermore, although the sheet portion 25 (sheet member) shown in Figure 4 has a two-layer structure consisting of a skin-side layer 25a (nonwoven fabric layer 25a) and a non-skin-side layer 25b (other layer 25b), the configuration of the sheet portion 25 is not limited to this, and it is sufficient to have at least a layer corresponding to the nonwoven fabric layer 25a. For example, the sheet portion 25 may have only one skin-side layer 25a (nonwoven fabric layer 25a). It may also have a third layer or other layers different from the nonwoven fabric layer 25a and the other layer 25b. In other words, the sheet portion 25 may have three or more layers.

[0061] <Regarding the skin-side fibers> As described above, in the sheet portion 25 of this embodiment, the skin-side layer 25a (nonwoven fabric layer 25a) is composed of non-heat-fusible fibers such as cotton fibers as the base fibers. In this embodiment, the non-heat-fusible fibers constituting the nonwoven fabric layer 25a have a shorter average fiber length and less variation in fiber length compared to conventional non-heat-fusible fibers. The detailed composition of the base fibers (skin-side fibers 25as) of the nonwoven fabric layer 25a will be described below.

[0062] First, we will briefly explain the conventional method for manufacturing cotton fibers, which are a common non-heat-fusible fiber. When manufacturing cotton fibers, first, raw cotton is obtained. Next, foreign matter such as seeds, leaves, and stems contained in the raw cotton is removed, and degreasing and bleaching are performed to produce bleached cotton. Then, this bleached cotton is entangled with a water flow on a nonwoven fabric base to produce cotton material.

[0063] Normally, when manufacturing bleached cotton, a carding process is performed using a carding machine (not shown) equipped with a rotating body having multiple thorns on its circumferential surface to scrape and loosen the compressed raw cotton fibers while removing foreign matter. At this time, the short fiber scraps scraped off by the carding machine are also called "combed noil". In the sheet portion 25 of this embodiment, this combed noil can be used as the base fiber of the nonwoven fabric layer 25a. Of course, the nonwoven fabric layer 25a may also be composed of non-heat-fusible fibers other than combed noil.

[0064] Furthermore, the nonwoven fabric layer 25a of the sheet portion 25 may contain combed noil as a base fiber, as well as other fibers. For example, combed noil may account for 50% (50% by weight) or more of the weight of the nonwoven fabric layer 25a, with the remainder being non-heat-fusible fibers other than combed noil or heat-fusible fibers such as polypropylene.

[0065] Figure 6A shows data measuring the distribution of fiber lengths of skin-side fibers constituting the nonwoven fabric layer 25a (skin-side layer 25a) in this embodiment, and Figure 6B shows data measuring the distribution of fiber lengths of skin-side fibers in the sheet member of the comparative example. Furthermore, Figure 7A is a graph showing the fiber length distribution of Figure 6A (this embodiment), and Figure 7B is a graph showing the fiber length distribution of Figure 6B (comparative example). The sheet member of the comparative example has a skin-side layer and a non-skin-side layer, and the base material fibers (skin-side fibers) of the skin-side layer are conventional non-heat-fusible fibers (cotton fibers, etc.) used in the sheet member (nonwoven fabric). In other words, the sheet member of the comparative example differs from the sheet portion 25 (sheet member) of this embodiment in that it uses ordinary non-heat-fusible fibers (cotton fibers, etc.), which are different from combed noil, as the base material fibers constituting the skin-side layer. Furthermore, the fiber length distribution data shown in Figures 6A and 6B can be obtained by measuring the fiber length based on the method using a fiber sorter as specified in "JIS L1019:2006 Cotton Fiber Testing Methods," section 7.2.

[0066] As shown in Figures 6 and 7, the average fiber length of the base fibers (non-heat-fusible fibers) constituting the nonwoven fabric layer 25a in the sheet portion 25 of this embodiment was 10.99 mm, and the standard deviation was 4.69. On the other hand, in the sheet member of the comparative example, the average fiber length of the base fibers (non-heat-fusible fibers) constituting the skin-side layer was 14.96 mm, and the standard deviation was 7.66. From this, it can be confirmed that the non-heat-fusible fibers, which are the base fibers of the nonwoven fabric layer 25a of this embodiment, have a shorter average fiber length and less variation in distribution than the non-heat-fusible fibers, which are the base fibers of the nonwoven fabric layer of the comparative example.

[0067] <Regarding the pilling of the skin-side layer 25> In the sheet portion 25 provided in the diaper 1 of this embodiment, the skin-side layer 25a (nonwoven fabric layer 25a) has skin-side fibers 25as with a short average fiber length as the base fibers, which makes it less likely to pill compared to conventional nonwoven fabrics with a long average fiber length. The pilling that occurs in the skin-side layer 25a of the sheet portion 25 will be described below.

[0068] In general, nonwoven fabric sheets tend to fray when their surface rubs against an opposing surface (such as the wearer's skin or clothing). For example, the sheet portion 25 of diaper 1 is designed so that the nonwoven fabric layer 25a is exposed to the skin side (see Figures 3 and 4), and when diaper 1 is worn, the skin-side layer 25a and the wearer's skin are in opposing positions. When the wearer moves their body in this state, the skin-side layer 25a and the wearer's skin rub against each other, causing some of the fibers on the surface (skin side) of the nonwoven fabric layer 25a to stand up in the thickness direction, resulting in fraying.

[0069] Therefore, an experiment was conducted to compare the amount of fluffing (fluffing height) between the sheet portion 25 (sheet member) of this embodiment and the sheet member of the comparative example. Specifically, for the sheet portion 25 of this embodiment described in Figure 6A and the sheet member of the comparative example described in Figure 6B, a fluffing height measurement test was conducted in which the surface was rubbed under predetermined conditions to generate fluffing, and the height of the resulting fluff was measured to compare the fluffing. Figures 8A to 8D are diagrams illustrating the test method for the fluffing height measurement test.

[0070] In the fluff height measurement test, the sheet material is first rubbed to create fluff on the surface. Here, a commercially available friction fastness tester (for example, the AB301 Gakushin-type friction fastness tester manufactured by Tester Sangyo Co., Ltd.) is used to rub the sheet material in accordance with the "Test Method for Color Fastness to Friction" specified in JIS L 0849. The test is performed in a dry state (dry test).

[0071] First, a friction fastness measuring instrument (hereinafter also referred to as friction tester 100) as shown in Figure 8A is prepared. The friction tester 100 has a test piece stand 101, friction elements 102, a friction element support part 103, and a drive part (not shown). The test piece stand 101 is a stand made of stainless steel and has a mounting surface 101f on its top surface for placing a test piece (sheet member). The mounting surface 101f is a smooth surface (curved surface) having a predetermined curvature (for example, radius of curvature R = 200 mm) along the first direction, as shown in Figure 8A. Above the test piece stand 101, a plurality (four in Figure 8A) of friction elements 102 are arranged at intervals in the second direction. Each friction element 102 has a friction surface 102f for friction with the test piece (sheet member). The friction surface 102f is a surface that can face the mounting surface 101f of the test specimen stand 101 when the friction test is performed, and is a surface (curved surface) having a predetermined curvature (for example, radius of curvature R = 45 mm). In the friction testing machine 100 of this embodiment, the friction surface 102f has a size of 20 mm × 20 mm. The friction element 102 is rotatably supported so as to face the mounting surface 101f of the test specimen stand 101, with the friction element support part 103 as the axis of rotation. The drive unit generates a driving force that moves the test specimen stand 101 back and forth along the first direction.

[0072] Next, as shown in Figure 8B, the sheet member that will become the test piece is placed and fixed on the mounting surface 101f of the test piece holder 101. In this embodiment, a 2 mm thick urethane sheet (for example, SL-80-4YT-H manufactured by BANGKOK FOAM CO., LTD.) is laid on the mounting surface 101f, and the edges of the urethane sheet are fixed with cellophane tape or the like. Then, the sheet portion 25 is placed on the urethane sheet with the skin-side layer 25a (nonwoven fabric layer 25a) facing upwards, and both ends in the first direction are fixed along the second direction with cellophane tape or the like. In addition, cloth tape 110 is attached to the friction surface 102f of the abrasive element 102. As the cloth tape 110, for example, Nitto Denko Corporation's Packaging Cloth Tape No. 753 can be used, and the adhesive side of the cloth tape 110 is attached to the friction surface 102f without wrinkles.

[0073] After the test specimen (sheet portion 25) is fixed to the mounting surface 101f of the test specimen stand 101 and the cloth tape is attached to the friction surface 102f of the friction element 102, the friction element 102 is rotated around the friction element support portion 103 as the axis of rotation, as shown in Figure 8B, so that the friction surface 102f (cloth tape 110) faces the mounting surface 101f (sheet portion 25). At this time, the cloth tape 110 is pressed against the sheet portion 25 from the vertically upward side to the downward side due to the weight of the friction element 102 (approximately 200g). Note that in Figure 8B, only one of the multiple friction elements 102 is facing the mounting surface 101f, but multiple friction elements 102 may be facing each other. Furthermore, although the sheet portion 25 is placed over almost the entire mounting surface 101f in Figure 8B, it is sufficient that the sheet portion 25 is placed (fixed) within the range in which at least one friction element 102 moves relative to the test piece stand 101 (reciprocating movement).

[0074] Next, the drive unit is driven, and the friction element 102 (friction element support part 103) is moved back and forth 50 times along the first direction at a speed of about 30 cpm on the mounting surface 101f as shown in Figure 8C. For example, before starting the drive, if the initial position ML in the first direction is defined as the position where the friction surface 102f (cloth tape 110) is in contact with the sheet part 25, the test piece stand 101 is moved back and forth 50 mm on both sides in the first direction from the initial position ML to rub the sheet part 25. Then, after the friction element 102 has been moved back and forth 50 times in the first direction, the movement of the friction element 102 is stopped at the initial position ML.

[0075] Next, the sheet portion 25 is removed from the test piece stand 101, and the sheet portion 25 is folded with the initial position ML as the fold line, as shown in Figure 8D, so that the skin-side layer 25a (nonwoven fabric layer 25a) is convex upwards. Then, from one side in the first direction, a predetermined area X including the initial position ML (fold line) of the sheet portion 25 is imaged using a microscope or digital camera, etc., and image data is acquired. It is preferable to acquire image data at multiple locations in the area X that has been rubbed by the friction element 102, while shifting the area X in the second direction.

[0076] Figures 9A and 9B are enlarged views of the area X of the sheet member after the test, as captured in Figure 8D. Figure 9A is an image showing the results of a fluff height measurement test performed on the sheet portion 25 of this embodiment, and Figure 9B is an image showing the results of a fluff height measurement test performed on the sheet member of the comparative example.

[0077] Image data obtained in the fluff height measurement test is divided into a grid-like area of ​​a predetermined size, and image analysis is performed. In Figures 9A and 9B, the area is divided into a grid-like area consisting of 11 rows arranged vertically (1 to 11) and 14 columns arranged horizontally (A to N). The size of each divided square is 1 mm x 1 mm. Furthermore, for example, the square located in the 2nd row and column D will be referred to as the (2D square) in this explanation.

[0078] In image analysis, the first step is to identify the fiber with the highest fluff height in the image data. Specifically, the fiber that reaches the highest position (mass) in the vertical direction in the image data is identified. In Figure 9A, the fiber extending from the bottom to the top (mass 5H) in the vertical direction is the fiber with the highest fluff height. In this case, the position of the fluff tip of the fiber with the highest fluff height is (mass 5H).

[0079] Next, the starting point of the fluffiness of the fiber with the highest fluffiness is determined. Here, the starting point of the fluffiness is defined as a predetermined distance downward along the vertical direction from the tip of the fluffiness. For example, in Figure 9A, if the tip of the fluffiness is (5H square), then any square located in rows 1 to 4 of column H (any of squares 1H to 4H) will be the starting point of the fluffiness. The starting point of the fluffiness is determined by performing a density analysis on the four target squares (1H to 4H squares). As a method of density analysis, for example, areas where fibers are present are defined as white, and areas where fibers are not present are defined as black, and it is determined whether the number of white pixels exceeds 50% of all pixels constituting each square. Then, squares where the number of white pixels exceeds 50% of all pixels are defined as having fibers, and squares where the number of white pixels is 50% or less are defined as not having fibers. In Figure 9A, in squares 1H to 4H, squares 1H and 2H are determined to be squares where fibers are present, while squares 3H and 4H are determined to be squares where fibers are not present. Of the squares 1H and 2H where fibers are present, square 2H, located on the upper side in the vertical direction, is determined to be the starting point for the fluffing. In other words, a square where 50% or more of the fibers are present is used as the base point, and the fibers are assumed to stand up vertically from that square upwards. As a result, in Figure 9A, the maximum fluffing height of the fibers in the nonwoven fabric layer 25a of the sheet portion 25 is 3 mm (the distance from square 2H, which is the starting point for the fluffing, to square 5H, which is the tip of the fluffing). If image data has been acquired for multiple measurement points, the fluffing height should be measured for each image data point and the average value should be calculated.

[0080] Similarly, the maximum fluff height of the comparative sheet material can be determined. In Figure 9B, the position of the tip of the fluff of the fiber with the highest fluff height is (10K square). On the other hand, the starting position of the fluff is (1K square). In other words, in the nonwoven fabric layer of the comparative sheet material, the maximum fluff height of the fibers is 9 mm (distance from the starting point of the fluffing, 1K square, to the tip of the fluffing, 10K square).

[0081] Therefore, it was found that in the sheet portion 25 (nonwoven fabric layer 25a) of this embodiment, the maximum height (3 mm) when fiber fuzzing occurs is smaller than the maximum height (9 mm) when fiber fuzzing occurs in the sheet member of the comparative example, indicating that fuzzing is less likely to occur.

[0082] Furthermore, if the maximum fluff height obtained from the fluff height measurement test is hf, the average fiber length is hs, and the length of the non-fluffy portion of the fiber with the highest fluff height is hn, then hn = hs - hf. In the nonwoven fabric layer 25a of the sheet portion 25, hs = 10.99 mm (see Figure 7A) and hf = 3 mm (see Figure 9A), so hn = 7.99 mm. In other words, in the sheet portion 25 (nonwoven fabric layer 25a) of this embodiment, even when fluffing occurs, the length of the fluffiest part of the fiber, hf (= 3 mm), is shorter than the length of the non-fluffy part, hn (= 7.99 mm) (hf < hn).

[0083] If the length hf of the fluffy portion of the fiber is longer than the length hn of the non-fluffy portion, then when the nonwoven fabric layer rubs against the wearer's clothing or skin, the fluffy portion will be more easily pulled by friction, and the entire fiber may easily fall out of the nonwoven fabric layer 25a. For example, in the comparative example sheet material, the average fiber length hs = 14.96 mm (see Figure 7B), and the length hf of the fluffiest portion of the fiber = 9 mm (see Figure 9B), so the length hn of the non-fluffy portion of the fiber = 14.96 mm - 9 mm = 5.96 mm. In other words, since the length hf (= 9 mm) of the fluffy portion of the fiber is longer than the length hn (= 5.96 mm) of the non-fluffy portion (hf > hn), when the sheet surface is rubbed, the fluffy fiber will be more easily pulled, and there is a high possibility that the entire fiber will fall out of the nonwoven fabric layer.

[0084] In contrast, as in this embodiment, if the length hf of the fuzzy portion is shorter than the length hn of the non-fuzzy portion (hf < hn), even if the nonwoven fabric layer 25a rubs against the wearer's skin, a large frictional force is less likely to act on the fuzzy portion. Furthermore, the non-fuzzy portion is more likely to be entangled with other fibers in the sheet portion 25, so even if the fuzzy portion is pulled, the non-fuzzy portion can more easily resist the tensile force. Therefore, the shedding of fibers is more easily suppressed, and the durability of the sheet portion 25 can be increased.

[0085] Furthermore, focusing on non-heat-fusible fibers with a fiber length of 12 mm or less, in the nonwoven fabric layer 25a of this embodiment, the proportion (by weight) of fibers with a fiber length of 12 mm or less is 75% or more, significantly exceeding 50% (see Figure 6A). Because fibers with a short average fiber length (fibers of 12 mm or less) account for 75% or more (by weight), the fiber density tends to be high, and the inter-fiber distance within the nonwoven fabric layer 25a tends to be short. On the other hand, in the comparative sheet member, the proportion (by weight) of fibers with a fiber length of 12 mm or less is 45.6%, and since the proportion of longer fibers is higher than in the nonwoven fabric layer 25a, the fiber density tends to be lower than that of the nonwoven fabric layer 25a (see Figure 6B). Therefore, in the nonwoven fabric layer 25a, the fiber density tends to be higher compared to the conventional sheet member, and compared to the case where the average fiber length is greater than 12 mm, the fibers tend to intertwine more easily within the nonwoven fabric layer 25a, making it less likely for fuzzing to occur and less likely for fibers to fall out.

[0086] Thus, in the sheet portion 25 of this embodiment, the average fiber length of the fibers in the nonwoven fabric layer 25a is 12 mm or less, and the maximum value of the fiber fluff height hf is shorter than the value hn obtained by subtracting the maximum value of the fiber fluff height hf from the average fiber length hs. As a result, even though cotton fibers that are prone to fluffing are used, it becomes easier to realize a sheet portion 25 (sheet member) that is less prone to fluffing and has high durability. Furthermore, by using this sheet portion 25 (sheet member), it becomes possible to form a diaper 1 that is less prone to fluffing and has high durability.

[0087] Furthermore, the sheet portion 25 (sheet member) of this embodiment has a skin-side layer 25a (nonwoven fabric layer 25a) which is a layer that can come into contact with the wearer's skin when wearing the diaper 1, and a non-skin-side layer 25b (other layer 25b) which is provided on the non-skin side of the skin-side layer 25a. The skin-side layer 25a (nonwoven fabric layer 25a) has non-heat-fusible fibers (cotton fibers) with an average fiber length of 12 mm or less, and the non-skin-side layer 25b (other layer 25b) has non-skin-side fibers 25bs which have an average fiber length longer than the non-heat-fusible fibers (cotton fibers). As explained in Figure 4, the skin-side layer 25a (nonwoven fabric layer 25a) and the non-skin-side layer 25b (other layer 25b) are adjacent to each other in the thickness direction, and at their boundary, the fibers of the nonwoven fabric layer 25a (cotton fibers) and the non-skin-side fibers 25bs (heat-fusible fibers) of the other layer 25b are intertwined. In the sheet portion 25, it is preferable that 90% by weight or more of the fibers constituting the nonwoven fabric layer 25a are the above-mentioned non-heat-fusible fibers (cotton fibers), and 90% by weight or more of the fibers constituting the other layer 25b are the above-mentioned heat-fusible fibers.

[0088] With this configuration, the probability of non-heat-fusible fibers (cotton fibers) in the nonwoven fabric layer 25a becoming entangled with heat-fusible fibers that have a longer average fiber length than the cotton fibers increases. Therefore, even if fluffing occurs in the non-heat-fusible fibers (cotton fibers) in the nonwoven fabric layer 25a, the entanglement of these non-heat-fusible fibers (cotton fibers) with the heat-fusible fibers in the other layer 25b makes it easier to prevent the non-heat-fusible fibers (cotton fibers) from falling out of the nonwoven fabric layer 25a. Consequently, the durability of the sheet portion 25 (diaper 1) can be easily improved.

[0089] In this case, it is preferable that at least a portion of the non-heat-fusible fibers (cotton fibers) of the nonwoven fabric layer 25a penetrate to the other layer 25b in the thickness direction. In other words, it is preferable that at least a portion of the non-heat-fusible fibers (cotton fibers) of the nonwoven fabric layer 25a are present on the side of the other layer 25b that faces the nonwoven fabric layer 25a in the thickness direction.

[0090] Figure 10 is a magnified photograph of the cross-sectional structure of the skin-side layer 25a (nonwoven fabric layer 25a) and the non-skin-side layer 25b (other layer 25b) of the sheet portion 25. In Figure 10, it is shown that some of the fibers (cotton fibers) of the nonwoven fabric layer 25a located on the skin side in the thickness direction penetrate through the interface between the nonwoven fabric layer 25a and the other layer 25b, and reach the other layer 25b located on the non-skin side in the thickness direction (see, for example, the arrow portion shown in Figure 10). Of the fibers (cotton fibers) of the nonwoven fabric layer 25a, the fibers that penetrate to the other layer 25b have a higher probability of becoming entangled with the heat-fusible fibers in the other layer 25b, making it easier to suppress them from falling out of the nonwoven fabric layer 25a. Therefore, the durability of the sheet portion 25 (diaper 1) can be more easily improved.

[0091] Furthermore, it is preferable that the skin-side layer 25a (nonwoven fabric layer 25a) and the non-skin-side layer 25b (other layer 25b) are joined to each other by an adhesive. In this embodiment, an adhesive such as a hot melt adhesive is provided on the skin-side surface (the surface facing the nonwoven fabric layer 25a) of the non-skin-side layer 25b (other layer 25b), and the nonwoven fabric layer 25a and the other layer 25b are joined together. This makes it easier for the fibers (cotton fibers) of the nonwoven fabric layer 25a to be fixed by the adhesive at the boundary between the nonwoven fabric layer 25a and the other layer 25b. In particular, if the fibers (cotton fibers) of the nonwoven fabric layer 25a penetrate to the other layer 25b, the fibers are more firmly fixed by the adhesive present at the boundary between the two layers. As a result, the fibers (cotton fibers) of the nonwoven fabric layer 25a are less likely to fall out, and the durability of the sheet portion 25 (diaper 1) can be further improved.

[0092] Furthermore, in the sheet portion 25 before conducting the fluff height measurement test, it is preferable that the number of fibers (cotton fibers) per unit area protruding from the side of the nonwoven fabric layer 25a facing the other layer 25b (non-skin side) is greater than the number of fibers (cotton fibers) per unit area protruding from the side of the nonwoven fabric layer 25a that is exposed to the skin (skin side). If there are many fibers (cotton fibers) protruding from the nonwoven fabric layer 25a towards the skin, fluffing is more likely to occur when the skin side is rubbed during the fluff height measurement test, etc., so it is preferable to have as few fibers protruding towards the skin as possible. On the other hand, if there are many fibers (cotton fibers) protruding from the nonwoven fabric layer 25a towards the non-skin side, the probability of entanglement with the heat-fusible fibers of the other layer 25b increases, making it less likely for the cotton fibers to fall out, so it is preferable to have as many fibers protruding towards the non-skin side as possible. In other words, if the number of fibers (cotton fibers) protruding from the non-skin side per unit area is greater than the number of fibers (cotton fibers) protruding from the skin side per unit area in the nonwoven fabric layer 25a, then it is possible to make the sheet portion 25 (diaper 1) less prone to pilling. Furthermore, by making it more difficult for fibers to fall out, the durability of the sheet portion 25 (diaper 1) can be improved.

[0093] Furthermore, it is preferable that the non-skin-facing layer 25b (other layer 25b) of the sheet portion 25 has portions where the heat-fusible fibers constituting the other layer 25b are fused together. In the diaper 1 of this embodiment, for example, a spunbond nonwoven fabric can be used as the other layer 25b, which is made by randomly joining (fusing) heat-fusible fibers such as polyester fibers or polypropylene fibers obtained by melting and spinning raw materials together. In such a nonwoven fabric, having multiple portions where the fibers are fused together increases the rigidity of the sheet (non-skin-facing layer 25b) itself, thereby improving durability. When the non-heat-fusible fibers (cotton fibers) of the nonwoven fabric layer 25a penetrate to the other layer 25b, the penetrating cotton fibers are more easily held in place by the heat-fusible fibers randomly joined in the other layer 25b, making it less likely for the cotton fibers to fall out. This improves the durability of the sheet portion 25 (diaper 1).

[0094] Furthermore, as explained in Figure 4, the skin-side layer 25a (nonwoven fabric layer 25a) of the sheet portion 25 (sheet member) is provided with a predetermined basis weight portion 25aP and a low basis weight portion 25aL, and when viewed in the thickness direction, both have portions that overlap with the non-skin-side layer 25b (other layers 25b). As shown in Figures 5A and 5B, the predetermined basis weight portion 25aP and the low basis weight portion 25aL are arranged alternately in the vertical direction (up and down direction of the diaper 1), and the predetermined basis weight portion 25aP and the low basis weight portion 25aL are arranged alternately in the horizontal direction (left and right direction of the diaper 1). By having the low basis weight portion 25aL dispersed on the surface of the sheet portion 25, the portion of the nonwoven fabric layer that comes into contact with the wearer's skin and clothing can be reduced compared to the case where the low basis weight portion 25aL is not present. As a result, a large frictional force acting on the surface of the sheet portion 25 is suppressed, and the possibility of fibers falling out of the sheet portion 25 can be reduced. Therefore, the durability of the sheet portion 25 (diaper 1) can be improved.

[0095] Furthermore, it is preferable that, before conducting the fluff height measurement test, the average fiber length of the fibers (cotton fibers) in the skin-side layer 25a (nonwoven fabric layer 25a) of the sheet portion 25 is longer than the maximum thickness of the sheet portion 25. In this embodiment, the average fiber length of the fibers before conducting the fluff height measurement test is 10.99 mm, while the thickness of the sheet portion 25 is about 2 to 4 mm, meaning the average fiber length of the fibers is longer than the thickness of the sheet portion 25. With this configuration, the fibers (cotton fibers) of the nonwoven fabric layer 25a are more likely to penetrate to the other layer 25b, increasing the probability of entanglement with the heat-fused fibers in the other layer 25b. Therefore, compared to the case where the average fiber length of the fibers (cotton fibers) of the sheet portion 25 is less than or equal to the maximum thickness of the sheet portion 25, the risk of fibers falling out of the sheet portion 25 is reduced, and the durability of the sheet portion 25 (diaper 1) can be improved.

[0096] Furthermore, the waist portions 20 and 30 of the diaper 1 are provided with stretchable members such as waist elastic members 23 and 33 that expand and contract in the left-right direction, but when viewed in the thickness direction, there is an overlapping portion between the stretchable members and the sheet portion 25 (see Figure 2). In the portions of the waist portions 20 and 30 where the waist elastic members 23 and 33 (stretchable members) are provided, wrinkles are more likely to form on the surface due to the contraction of the stretchable members, so the portion of the sheet portion 25 that comes into contact with the wearer's skin or clothing can be reduced. This reduces the risk of the fibers (cotton fibers) of the nonwoven fabric layer 25a falling out of the sheet portion 25, and improves the durability of the sheet portion 25 (diaper 1).

[0097] Furthermore, in Figure 14 (modification 4), which will be described later, the sheet member corresponding to the sheet portion 25 is used as the top sheet 12 of the absorbent body 10. The absorbent body 10 is provided with leg-circumference elastic members 15 (stretchable members) that expand and contract in the longitudinal direction on both sides in the left-right direction, but when viewed in the thickness direction, there is a portion in which the stretchable members and the sheet portion 25 overlap (see Figure 14). As in the case described above, in the portion in which the leg-circumference elastic members 15 are provided, wrinkles are more likely to form on the surface due to the contraction of the stretchable members, so the portion of the sheet portion 25 that comes into contact with the wearer's skin or clothing can be reduced. This reduces the risk of the fibers (cotton fibers) of the nonwoven fabric layer 25a falling out of the sheet portion 25, and improves the durability of the sheet portion 25 (diaper 1).

[0098] Furthermore, in the nonwoven fabric layer 25a of the sheet portion 25, it is preferable that the basis weight of the non-heat-fusible fibers (cotton fibers) be greater than the basis weight of the fibers other than the non-heat-fusible fibers (cotton fibers). With such a configuration, the amount of fiber fusion in the nonwoven fabric layer 25a can be reduced compared to when the basis weight of the fibers other than the non-heat-fusible fibers (cotton fibers) is greater than the basis weight of the non-heat-fusible fibers (cotton fibers). In this case, the flexibility of the sheet portion 25 (nonwoven fabric layer 25a) can be increased, making it easier to improve the feel of the sheet portion 25 (diaper 1) against the skin.

[0099] Furthermore, in the sheet portion 25 of the diaper 1, it is preferable that the maximum value of the fiber fluff height of the nonwoven fabric layer 25a after the fluff height measurement test is three times or less the maximum value of the fiber fluff height of the nonwoven fabric layer 25a before the fluff height measurement test. With such a configuration, the length of the portion of the fiber (cotton fiber) that protrudes from the nonwoven fabric layer 25a can be shortened compared to the case where the maximum value of the fiber fluff height of the nonwoven fabric layer 25a after the fluff height measurement test is greater than three times the maximum value of the fiber fluff height of the nonwoven fabric layer 25a before the fluff height measurement test. As a result, the fiber (cotton fiber) is less likely to come out of the nonwoven fabric layer 25a, and the durability of the sheet portion 25 (diaper 1), which is prone to friction with the wearer's skin and clothing, can be improved.

[0100] Furthermore, in the sheet portion 25 of the diaper 1, it is preferable that the maximum value of the fluff height of the fibers in the nonwoven fabric layer 25a after the fluff height measurement test is 1 / 4 or less of the average fiber length of the fibers in the nonwoven fabric layer 25a. With such a configuration, compared to the case where the maximum value of the fluff height of the fibers is greater than 1 / 4 of the average fiber length of the fibers in the nonwoven fabric layer 25a, it becomes less likely for fibers (cotton fibers) to come out of the nonwoven fabric layer 25a, and the durability of the sheet portion 25 (diaper 1), which is prone to friction with the wearer's skin and clothing, can be improved.

[0101] <Regarding the arrangement of the sheet portion 25 in diaper 1> Figures 11 to 14 show modified examples of the arrangement of the sheet member in this embodiment. In each modified example, the sheet portion 25 is a sheet member having the above-described features.

[0102] (Modification 1) Figures 11A and 11B illustrate Modification 1 of the arrangement of the sheet portion 25. In Modification 1, no separate sheet member is provided as the sheet portion 25, and the folded portion 22r (32r) of the ventral outer layer sheet 22 (dorsal outer layer sheet 32) is made into the sheet portion 25 (35). In this Modification 1, at least the portion of the ventral outer layer sheet 22 (dorsal outer layer sheet 32) that becomes the sheet portion 25 (35) has a skin-side layer (cotton layer) 25a on the skin side and a non-skin-side layer 25b on the non-skin side in the thickness direction of the skin-side layer 25a. Furthermore, the sheet portion 25 (35), which is part of the ventral outer layer sheet 22 (dorsal outer layer sheet 32), and the inner layer sheet 21 (adjacent sheet member) adjacent to the sheet portion 25 (35) from the non-skin side in the thickness direction, are joined by welding or adhesive to a joint portion (not shown), and the sheet portion 25 (35) and the inner layer sheet 21 (adjacent sheet member) are not joined by welding or adhesive to a joint portion (not shown). With this configuration, the same effects and advantages as in the above-described embodiment can be obtained in the sheet portion 25.

[0103] In this modified example, the folded portion 22r (32r) of the sheet portion 25 (35) is a tightly constricting area on the ventral waist portion 20 (dorsal waist portion 30). Having a skin-side layer 25a on the skin-contacting surface of such an area allows the wearer to better feel the softness of the skin-side fibers 25as, such as cotton fibers. Furthermore, the non-jointed portion allows it to easily follow the movement of the waist, reducing friction with the skin and suppressing pilling of the skin-side fibers 25as, such as cotton fibers. In Modified Example 1, the sheet portion 25 (35) is replaced with a folded portion 22r (32r), but the invention is not limited to this. Whether or not the diaper 1 has a folded portion 22r (32r), the sheet portion 25 (35) may be positioned as shown in Figure 11.

[0104] (Modification 2) Figure 12 is a diagram illustrating modification 2 of the arrangement of the sheet portion 25. In modification 2 shown in Figure 12, the sheet portion 25 (35) is not provided to both ends in the left-right direction of the ventral waist portion 20 (dorsal waist portion 30), but is provided to the central part in the left-right direction of the ventral waist portion 20 (dorsal waist portion 30), and to straddle the upper end 10e of the absorbent body 10 in the vertical direction. Since the upper end 10e of the absorbent body 10 is a part where the irregularities are relatively large, by arranging the sheet portion 25 (35) so that at least the entire upper end 10e is covered, friction to the skin during wear can be suppressed and irritation to the skin can be reduced. Even with this configuration, the risk of fibers falling out during wear can be reduced and durability can be improved.

[0105] (Modification 3) Figure 13 is a diagram illustrating modification 3 of the arrangement of the sheet portion 25. In modification 3 shown in Figure 13, a sheet member that will become the sheet portion 25 (35) is provided between the absorbent main body 10 and the inner layer sheet 21. The sheet member that will become the sheet portion 25 is provided in the ventral waist portion 20 between one end of the pair of side joints SS in the left-right direction and the other end, and in the region from the upper end to the lower end in the vertical direction of the pair of side joints SS. In the dorsal waist portion 30, the sheet member that will become the sheet portion 35 is provided between one end of the pair of side joints SS in the left-right direction and the other end, and in the region from the upper end to near the lower end in the vertical direction of the pair of side joints SS. With this configuration, the skin-side layer 25a is present on most of the skin-contact surface in the ventral waist portion 20 (dorsal waist portion 30) other than the region where the absorbent main body 10 is located, improving the feel against the skin. Furthermore, because the sheet portion 25 (35) and the inner layer sheet 21 have non-jointed portions that are not joined by welding or adhesive, the sheet portion 25 (35) can easily follow the movement of the wearer's waist, reducing friction with the skin. This suppresses fluffing of the skin-side fibers 25as, such as cotton fibers, even if the proportion of the skin-side layer 25a in contact with the skin is large. In addition, in the waist portions 20 and 30, the sheet portions 25 and 35 may be placed as the sheets on the skin-side of the waist portions 20 and 30 instead of the inner layer sheets 21 and 31.

[0106] Furthermore, if the non-skin-facing fiber 25bs is a thermoplastic fiber, the diaper 1 may have an adjacent member provided at a position overlapping with the sheet portion 25 when viewed in the thickness direction, and the diaper 1 may have a welded joint where the sheet portion 25 and the adjacent member are welded together in the thickness direction, and the diaper 1 may be configured such that at least a part of the welded joint overlaps with the portion where the low basis weight portion 25aL and the non-skin-facing layer 25b overlap when viewed in the thickness direction. For example, in the modified examples 1 to 3 shown in Figures 11 to 13, when the inner layer sheet 21 (or ventral outer layer sheet 22) at a position overlapping with the sheet portion 25 of the ventral waist portion 20 when viewed in the thickness direction is the adjacent member, the sheet portion 25 and the inner layer sheet 21 (or ventral outer layer sheet 22) may have a welded joint (not shown) where they are welded together in the thickness direction. In such cases, it is preferable that at least a portion of the welded joint overlaps with the portion where the low basis weight portion 25aL of the sheet portion 25 and the non-skin side layer 25b overlap when viewed in the thickness direction. This reduces the risk of a decrease in the bonding strength of the welded joint that welds the sheet portion 25 and the inner layer sheet 21 (or outer layer sheet 22).

[0107] In the embodiments and modifications 1 to 3 described above, a sheet portion 25 is provided on the ventral waist portion 20 and a sheet portion 35 is provided on the dorsal waist portion 30, but the invention is not limited to this. Each diaper 1 may have a configuration in which the sheet portion 25 is provided only on the ventral waist portion 20 and the sheet portion 35 is not provided on the dorsal waist portion 30, or a configuration in which the sheet portion 35 is provided only on the dorsal waist portion 30 and the sheet portion 25 is not provided on the ventral waist portion 20.

[0108] (Modification 4) Figure 14 is a diagram illustrating modification 4 of the arrangement of the sheet portion 25. In modification 4 shown in Figure 14, the sheet portion 25 is provided as the top sheet 12 of the absorbent body 10. That is, in the diaper 1 of modification 4, the sheet member corresponding to the sheet portion 25 is provided on the skin side of the absorbent core 11 and covers the entire area of ​​the absorbent core 11. Since the top sheet 12 is the part of the absorbent body 10 that comes into contact with the wearer's skin, providing the sheet portion 25 as the top sheet 12 improves the feel against the skin with the skin-side fibers 25as of the skin-side layer 25a, while reducing discomfort to the wearer's skin and adverse effects on the wearer's skin. Furthermore, the risk of fibers falling off during wear is reduced in the top sheet 12 of the absorbent body 10, and durability is improved. This makes it easier to suppress discomfort during wear and a decrease in liquid absorbency.

[0109] Furthermore, the modified diaper 1 in Figure 14 (modification 4) may have a compression member having a portion (not shown) that is compressed in the thickness direction. Examples of the compression member include an absorbent core 11. In the diaper 1, a sheet portion 25 (top sheet 12) may be provided on the skin side of the compression member (absorbent core 11), and when viewed in the thickness direction, the portion that overlaps with the compressed portion of the compression member (absorbent core 11) may be in the portion that overlaps with the low basis weight portion 25aL and the non-skin side layer 25b. Generally, the compressed portion is a portion with a high fiber density, and therefore easily absorbs moisture by capillary action. For this reason, having a portion with a high density due to compression in the compression member (absorbent core 11) makes it easier to move moisture from the sheet portion 25 (top sheet 12) to the compression member located on the non-skin side of the sheet portion 25.

[0110] ===Other=== The above embodiments are provided to facilitate understanding of the present invention and are not intended to limit its interpretation. The present invention can be modified and improved without departing from its spirit, and it goes without saying that the present invention includes equivalents thereof.

[0111] In the above-described embodiment, a sheet member with an average fiber length of 12 mm or less was realized by using combed noil as the fibers constituting the sheet member (nonwoven fabric), but the invention is not limited to this. For example, conventional fibers other than combed noil (cotton fibers) may be classified (so-called graded) according to their length to achieve an average fiber length of 12 mm or less.

[0112] 1 Diaper (Pants-type disposable diaper, disposable absorbent item), 10 Absorbent body, 10e Upper end, 11 Absorbent core (absorbent material), 12 Top sheet, 13 Back sheet, 14 Outer sheet, 15 Leg elastic member, 18 Outer body, 20 Ventral waist section, 21 Inner layer sheet, 22 Ventral outer layer sheet, 22r Folded portion, 23 Waist elastic member, 25 Sheet section (sheet member), 25a Skin-side layer (nonwoven fabric layer), 25aL Low basis weight section, 25aP Determined basis weight section, 25as Skin-side fibers (cotton fibers, non-heat-fusible fibers), 25b Non-skin-side layer (other layers), 25bs Non-skin-side fibers, 30 Back waist section, 32 Back outer layer sheet, 32r Folded portion, 33 Body elastic member, 34 Rear leg elastic member, 35 Seat section (seat member), 40 Crotch area, 100 Friction testing machine, 101 Test piece stand, 101f Mounting surface, 102 Friction element, 102f Friction surface, 103 Friction element support, 110 Cloth tape, SS Side joint (joint)

Claims

1. An absorbent article comprising: a liquid-absorbing absorbent core; and a sheet member provided on the skin-side or non-skin-side of the absorbent core, wherein the sheet member has a nonwoven fabric layer comprising a plurality of non-heat-fusible fibers; the nonwoven fabric layer has a surface exposed to the skin-side or non-skin-side; the average fiber length of the fibers in the nonwoven fabric layer is 12 mm or less; and the maximum value of the fluff height of the fibers in the nonwoven fabric layer after a fluff height measurement test is shorter than the value obtained by subtracting the maximum value of the fluff height of the fibers in the nonwoven fabric layer from the average fiber length of the fibers in the nonwoven fabric layer.

2. An absorbent article according to claim 1, wherein in an unfolded and stretched state, it has a longitudinal direction, a left-right direction and a thickness direction that are mutually orthogonal, the sheet member has other layers at different positions in the thickness direction, the other layers comprise heat-fusible fibers having an average fiber length longer than the fibers of the nonwoven fabric layer, the non-heat-fusible fibers and the heat-fusible fibers have entangled portions, 90% by weight or more of the fibers constituting the nonwoven fabric layer are the non-heat-fusible fibers, and 90% by weight or more of the fibers constituting the other layer are the heat-fusible fibers.

3. An absorbent article according to claim 2, characterized in that, of the other layers, at least a portion of the fibers of the nonwoven fabric layer are present on the surface facing the nonwoven fabric layer in the thickness direction.

4. An absorbent article according to claim 3, characterized in that an adhesive is provided on the opposing surface of the other layer.

5. An absorbent article according to claim 3, characterized in that, in the sheet member before the fluffing height measurement test, the number of fibers per unit area of ​​the nonwoven fabric layer protruding from the surface of the nonwoven fabric layer facing the other layer is greater than the number of fibers per unit area of ​​the nonwoven fabric layer protruding from the exposed surface of the nonwoven fabric layer.

6. An absorbent article according to claim 2, wherein the other layer has portions in which the heat-fusible fibers are fused together.

7. An absorbent article according to claim 2, wherein the nonwoven fabric layer has a predetermined basis weight portion having fibers of the nonwoven fabric layer with a predetermined basis weight, and a low basis weight portion having fibers of the nonwoven fabric layer with a lower basis weight than the predetermined basis weight portion, wherein the predetermined basis weight portion and the low basis weight portion are arranged alternately in the longitudinal direction, and wherein the predetermined basis weight portion and the low basis weight portion are arranged alternately in the left-right direction.

8. An absorbent article according to any one of claims 1 to 4, characterized in that the average fiber length of the fibers in the nonwoven fabric layer is longer than the maximum thickness of the sheet member before the fluffing height measurement test.

9. An absorbent article according to any one of claims 1 to 4, wherein the sheet member is provided on the skin side of the absorbent core and covers the entire area of ​​the absorbent core.

10. An absorbent article according to any one of claims 1 to 4, characterized in that, in an unfolded and extended state, it has a longitudinal direction, a left-right direction and a thickness direction which are mutually orthogonal, and has an expandable / contractable member that is expandable / contractible in at least one of the longitudinal direction or the left-right direction, and in the thickness direction, the sheet member has a portion that overlaps with the expandable / contractable member.

11. An absorbent article according to any one of claims 1 to 4, characterized in that, in the nonwoven fabric layer, the basis weight of the non-heat-fusible fibers is greater than the basis weight of the fibers of the nonwoven fabric layer other than the non-heat-fusible fibers.

12. An absorbent article according to any one of claims 1 to 4, characterized in that the maximum value of the fluff height of the fibers of the nonwoven fabric layer after the fluff height measurement test is three times or less the maximum value of the fluff height of the fibers of the nonwoven fabric layer before the fluff height measurement test.

13. An absorbent article according to any one of claims 1 to 4, characterized in that the maximum value of the fluff height of the fibers of the nonwoven fabric layer after the fluff height measurement test is 1 / 4 or less of the average fiber length of the fibers of the nonwoven fabric layer.

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