Nonwoven fabric for liquid-permeable sheet of absorbent article

Abstract

Provided is a non-woven fabric for a liquid permeable sheet of an absorbent article that has excellent water-absorbing properties and inhibits sticking to the skin of a wearer. This non-woven fabric 10 comprises a first fiber layer 26 and a second fiber layer 28, wherein the first fiber layer 26 is made of thermoplastic resin fibers, and the second fiber layer 28 contains water-absorbent fibers and thermoplastic resin fibers, and has a plurality of protrusions 30 and a plurality of recesses 32. In the case in which a load is not added in the thickness direction to the non-woven fabric 10 when the thickness of the first fiber layer 26 at the plurality of protrusions 30 and the thickness of the first fiber layer 26 at the plurality of recesses 32 are defined as Tc1 and Td1, respectively, and in the case in which a load of 2.9 kPa is added to the non-woven fabric 10 in the thickness direction when the thickness of the first fiber layer 26 at the plurality of protrusions 30 and the thickness of the first fiber layer 26 at the plurality of recesses 32 are defined as Tc2 and Td2, respectively, the non-woven fabric 10 satisfies the relational expression of (Tc2 / Tc1)<(Td2 / Td1).

Description

[Technical field]

[0001] The present invention relates to a nonwoven fabric for a liquid-permeable sheet in an absorbent article. [Background technology]

[0002] 2. Description of the Related Art In absorbent articles such as disposable diapers and sanitary napkins, the use of a two-layer nonwoven fabric as a material for a liquid-permeable sheet such as a topsheet has been considered.

[0003] For example, Patent Document 1 discloses a nonwoven fabric for absorbent articles which includes a first fiber layer and a second fiber layer located on one main surface of the first fiber layer, the first fiber layer including first sheath-core conjugate fibers, the second fiber layer including second sheath-core conjugate fibers and cellulosic fibers, the first sheath-core conjugate fibers having a smaller fineness than the second sheath-core conjugate fibers, the first sheath-core conjugate fibers having a fineness of 1.0 to 2.8 dtex, the second sheath-core conjugate fibers having a fineness of 1.7 to 5.6 dtex, and the cellulosic fibers having a fineness of 1.2 to 6.0 dtex, and the second fiber layer including 5% by mass to 40% by mass of the cellulosic fibers based on the total mass of the second fiber layer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-171688 A Summary of the Invention [Problem to be solved by the invention]

[0005] In addition to liquid excrement such as menstrual blood excreted from the wearer, moisture such as sweat excreted from the wearer's skin is supplied to the absorbent article.

[0006] In the nonwoven fabric of Patent Document 1, the thickness of the first fiber layer is uniform in the surface direction, so when the first fiber layer is thick, the first fiber layer can receive the excrement and transfer it to the absorbent on the non-skin-facing side, but there is a concern that the first fiber layer will hinder the water absorption by the cellulosic fiber, and moisture such as sweat will remain between the wearer's skin and the absorbent article, causing discomfort to the wearer due to sweat steaming. When the first fiber layer is thin, the cellulosic fiber is close to the wearer's skin, so water absorption by the cellulosic fiber is obtained, but there is a risk that the cellulosic fiber that has absorbed moisture such as sweat will cause the surface of the wet nonwoven fabric to stick to the wearer's skin, causing the wearer to experience a rash or itchiness.

[0007] An object of the present invention is to provide a nonwoven fabric for a liquid-permeable sheet of an absorbent article which has excellent water absorbency and is prevented from sticking to the skin of a wearer. [Means for solving the problem]

[0008] The present invention relates to a nonwoven fabric for a liquid-permeable sheet of an absorbent article, the nonwoven fabric comprising a first fiber layer and a second fiber layer in this order in a thickness direction, the first fiber layer being made of a thermoplastic resin fiber and having a first surface which is a skin-facing surface of the liquid-permeable sheet, the second fiber layer including a water-absorbent fiber and a thermoplastic resin fiber and having a second surface which is a non-skin-facing surface of the liquid-permeable sheet, the first surface having a plurality of solid protrusions protruding in a direction from the second surface toward the first surface and a plurality of recesses recessed in a direction from the first surface toward the second surface, the thickness of the first fiber layer at the plurality of recesses being a thickness of the first fiber layer being a thickness of the first fiber layer being a thickness of the first fiber layer being a thickness of the second ... is thinner than the thickness of the first fiber layer at the multiple protrusions, and in the nonwoven fabric to which no load is applied in the thickness direction, the thicknesses of the first fiber layer at the multiple protrusions and the thicknesses of the first fiber layer at the multiple recesses are Tc1 and Td1, respectively, and in the nonwoven fabric to which a load of 2.9 kPa is applied in the thickness direction, the thicknesses of the first fiber layer at the multiple protrusions and the thicknesses of the first fiber layer at the multiple recesses are Tc2 and Td2, respectively, so that the nonwoven fabric satisfies the relational expression (Tc2 / Tc1)<(Td2 / Td1). Effect of the Invention

[0009] The nonwoven fabric according to the present invention has excellent water absorbency and is prevented from sticking to the wearer's skin. [Brief description of the drawings]

[0010] [Figure 1] 1 is a diagram showing a schematic diagram of an absorbent article according to an embodiment. [Diagram 2] FIG. 1 is a plan view illustrating a nonwoven fabric according to an embodiment of the present invention. [Diagram 3] 3 is a partial cross-sectional view showing a schematic cross section taken along line III-III in FIG. 2. [Figure 4] 3 is a partial cross-sectional view showing a schematic cross section taken along line III-III in FIG. 2, illustrating a state in which a load is applied to the nonwoven fabric in the thickness direction. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The embodiments of the present invention relate to the following aspects.

[0012] [Aspect 1] A nonwoven fabric for a liquid-permeable sheet of an absorbent article, comprising a first fiber layer and a second fiber layer in that order in a thickness direction, the first fiber layer is made of thermoplastic resin fibers and has a first surface that serves as a skin-facing surface of the liquid-permeable sheet; the second fiber layer includes water-absorbent fibers and thermoplastic resin fibers, and has a second surface that is a non-skin facing surface of the liquid-permeable sheet; the first surface has a plurality of solid protruding portions protruding in a direction from the second surface toward the first surface, and a plurality of recessed portions recessed in a direction from the first surface toward the second surface, a thickness of the first fiber layer in the recessed portions is smaller than a thickness of the first fiber layer in the protruding portions; A nonwoven fabric which satisfies the relational expression (Tc2 / Tc1)<(Td2 / Td1), where the thickness of the first fiber layer at the plurality of protruding portions and the thickness of the first fiber layer at the plurality of recessed portions are Tc1 and Td1, respectively, in the nonwoven fabric to which no load is applied in the thickness direction, and the thickness of the first fiber layer at the plurality of protruding portions and the thickness of the first fiber layer at the plurality of recessed portions are Tc2 and Td2, respectively, in the nonwoven fabric to which a load of 2.9 kPa is applied in the thickness direction.

[0013] The nonwoven fabric comprises a first fiber layer and a second fiber layer, the first fiber layer being made of thermoplastic resin fibers, and the second fiber layer containing absorbent fibers and thermoplastic resin fibers and having a plurality of convex portions and a plurality of concave portions. Therefore, when the nonwoven fabric is used as a liquid-permeable sheet (e.g., a top sheet, etc.) of an absorbent article, the convex portions on the skin-facing surface (first surface) come into contact with the wearer's skin, and the thermoplastic resin fibers of the convex portions receive excrement such as menstrual blood excreted from the wearer and transfer the excrement through the second fiber layer to the absorbent located on the non-skin-facing surface (second surface). Moisture such as sweat discharged from the wearer's skin reaches the recesses mainly directly or along the first surface from the wearer's skin, unlike excrement such as menstrual blood, in the form of droplets or steam, rather than migrating in the thickness direction through the first fiber layer. In this nonwoven fabric, the thickness of the first fiber layer in the recesses is thinner than the thickness of the first fiber layer in the protruding portions, and therefore the distance from the first surface to the second fiber layer in the recesses is shorter than the distance from the first surface to the second fiber layer in the protruding portions, and moisture such as sweat easily reaches the second fiber layer in the recesses. Therefore, in this nonwoven fabric, the absorbent fibers contained in the second fiber layer in the recesses easily absorb moisture such as sweat discharged from the wearer's skin, and further, the thermoplastic resin fibers contained in the second fiber layer transfer the moisture to the absorbent located on the non-skin-facing surface (second surface) side. In this nonwoven fabric, the thickness of the first fiber layer in the convex portions and the thickness of the first fiber layer in the concave portions before and after applying a load in the thickness direction satisfy the above-mentioned relational expression, so that the first fiber layer in the convex portions is reduced in thickness more than the first fiber layer in the concave portions. Therefore, when this nonwoven fabric is subjected to the wearer's body pressure, the distance from the first surface to the second fiber layer is also short in the convex portions, so that moisture such as sweat discharged from the wearer's skin can easily reach the second fiber layer through the first fiber layer in the convex portions. A part of the moisture is absorbed by the water-absorbent fiber contained in the second fiber layer, and the other part is transferred to the absorbent located on the non-skin-facing surface (second surface) side by the thermoplastic resin fiber contained in the second fiber layer. In this way, when this nonwoven fabric is subjected to the wearer's body pressure, the water-absorbent fiber can absorb moisture such as sweat discharged from the wearer's skin even in the convex portions. Even when the second fiber layer absorbs moisture such as sweat and excrement excreted by the wearer, the first fiber layer in the convex portion holds the absorbent fibers contained in the second fiber layer away from the wearer's skin, thereby preventing the first surface from sticking to the wearer's skin. As described above, the present nonwoven fabric has excellent water absorbency and can provide a nonwoven fabric for a liquid-permeable sheet of an absorbent article that is prevented from sticking to the skin of the wearer.

[0014] [Aspect 2] The basis weight of each of the first fiber layer and the second fiber layer is uniform in a surface direction, 2. The nonwoven fabric of claim 1, wherein when a load of 2.9 kPa is applied in the thickness direction of the nonwoven fabric, a thickness of the first fiber layer in the plurality of convex portions is thinner than a thickness of the first fiber layer in the plurality of concave portions.

[0015] In the convex portions of the nonwoven fabric, the basis weights of the first and second fiber layers are uniform in the surface direction, and the thickness of the first fiber layer in the convex portions is thinner than that of the first fiber layer in the convex portions, i.e., the thickness of the first fiber layer in the convex portions is thicker than that of the first fiber layer in the concave portions, so that the fiber density of the first fiber layer in the convex portions is lower than that of the concave portions, and the convex portions are more likely to deform in the thickness direction. Moreover, since the load in the thickness direction acts on the convex portions from the first and second surfaces, the thickness of the convex portions is more likely to decrease than that of the concave portions when a load is applied in the thickness direction. On the other hand, in the concave portions, the basis weights of the first and second fiber layers are uniform in the surface direction, and the thickness of the first fiber layer in the concave portions is thinner than that of the first fiber layer in the convex portions, so that the fiber density of the first fiber layer in the concave portions is high and the first fiber layer is less likely to deform in the thickness direction. Furthermore, in the nonwoven fabric, as long as the convex portions protrude in the thickness direction from the concave portions on the first surface, the load in the thickness direction hardly acts on the concave portions. Therefore, even when a load is applied in the thickness direction of the nonwoven fabric, the thickness of the first fiber layer in the recesses is less likely to change than the thickness of the first fiber layer in the protrusions. When a load of 2.9 kPa is applied in the thickness direction, the nonwoven fabric maintains a shape in which the convex portions on the first surface protrude in the thickness direction more than the concave portions, while the thickness of the first fiber layer at the convex portions decreases, and the thickness of the first fiber layer at the convex portions becomes thinner than the thickness of the first fiber layer at the concave portions, so that the distance from the first surface to the second fiber layer becomes shorter even at the convex portions. Therefore, when the nonwoven fabric is subjected to the body pressure of the wearer, the absorbent fibers can absorb moisture such as sweat discharged from the wearer's skin even at the convex portions.

[0016] [Aspect 3] 3. The nonwoven fabric of claim 1 or 2, wherein in the nonwoven fabric subjected to a load of 2.9 kPa in the thickness direction, the deepest portions of the plurality of recesses are located at a position recessed from the first surface toward the second surface relative to the highest portions of the plurality of protrusions. When a load of 2.9 kPa is applied in the thickness direction of the nonwoven fabric, i.e., when the fabric is subjected to the wearer's body pressure, the convex portions bear the load while maintaining a shape in which the deepest parts of the multiple concave portions are recessed toward the second surface from the highest parts of the multiple convex portions. Therefore, the nonwoven fabric prevents the concave portions from touching the wearer's skin, thereby preventing the nonwoven fabric from sticking to the wearer's skin.

[0017] [Aspect 4] Aspect 4. The nonwoven fabric according to any one of aspects 1 to 3, wherein the second fiber layer contains 30% by mass to 70% by mass of the water-absorbent fiber. The nonwoven fabric contains 30% to 70% by mass of absorbent fibers and thermoplastic resin fibers in the second fiber layer, so that moisture such as sweat discharged from the wearer's skin is absorbed by the absorbent fibers, while excrement discharged from the wearer is transferred to the non-skin-facing side by the thermoplastic resin fibers.

[0018] [Aspect 5] a fiber diameter of the thermoplastic resin fiber of the second fiber layer is smaller than a fiber diameter of the thermoplastic resin fiber of the first fiber layer; Aspects 5. The nonwoven fabric according to any one of aspects 1 to 4, wherein in each of the first fiber layer and the second fiber layer, intersections of the thermoplastic resin fibers are thermally bonded. In the second fiber layer, the thermoplastic resin fibers are easily thermally bonded to each other due to the smaller fiber diameter, and therefore there are more joints where the intersections of the thermoplastic resin fibers are thermally bonded than in the first fiber layer, making it less likely to deform. On the other hand, the first fiber layer is more easily deformed because the thermoplastic resin fibers are more easily thermally bonded to each other than in the second fiber layer due to the larger fiber diameter, making it more likely to deform. Therefore, in this nonwoven fabric, the first fiber layer, which is easily deformed at the convex portions, is supported from the second surface by the second fiber layer, which is less likely to deform. Therefore, when a load is applied in the thickness direction, the thickness of the convex portions decreases, thereby shortening the distance from the first surface to the second fiber layer even at the convex portions, and the absorbent fibers can absorb moisture such as sweat discharged from the wearer's skin.

[0019] [Aspect 6] The nonwoven fabric according to any one of aspects 1 to 5, further comprising a third layer made of thermoplastic resin fibers on the second surface side. Since the nonwoven fabric has a third fiber layer on the second surface side, when the nonwoven fabric is subjected to the wearer's body pressure, the second and third fiber layers support the first fiber layer from the second surface side at the convex portions, and therefore, when a load is applied in the thickness direction, the thickness of the first fiber layer at the convex portions is likely to decrease. Therefore, when the nonwoven fabric is subjected to the wearer's body pressure, the distance from the first surface to the second fiber layer becomes short even at the convex portions, and the absorbent fibers can absorb moisture such as sweat discharged from the wearer's skin.

[0020] [Aspect 7] 7. The nonwoven fabric of any one of aspects 1 to 6, wherein a portion of the water-absorbent fiber is exposed from the first surface. Since part of the absorbent fibers of this nonwoven fabric is exposed from the first surface, when the fabric is used as a liquid-permeable sheet for an absorbent article, moisture such as sweat discharged from the wearer's skin is easily transferred to the second fiber layer through the part of the absorbent fibers exposed from the skin-facing surface (first surface), resulting in excellent absorbency.

[0021] Hereinafter, a nonwoven fabric for a liquid-permeable sheet of an absorbent article according to an embodiment will be described in detail with reference to the drawings.

[0022] (Structure of sanitary napkins) The absorbent article 1 shown in Fig. 1 is a sanitary napkin, and has a longitudinal direction L, a width direction W, and a thickness direction T that are perpendicular to each other, and includes a main body portion 1A extending in the longitudinal direction L, and a pair of flap portions 1B extending on both sides of the width direction W at approximately the center of the longitudinal direction L. The longitudinal direction L, width direction W, and thickness direction T of the absorbent article 1 coincide with the longitudinal direction, width direction, and thickness direction of each material described below, and therefore, hereinafter, the longitudinal direction L, width direction W, and thickness direction T are commonly used for the absorbent article 1 and each material thereof. The terms "skin-facing side" and "non-skin-facing side" refer to the side relatively closer to and farther from the wearer's skin surface in the thickness direction T, respectively, when the absorbent article 1 is worn by the wearer of the absorbent article 1, and are commonly used for each material of the absorbent article 1. In this specification, the "skin-facing surface" and the "non-skin-facing surface" of an absorbent article and each of the materials that constitute the absorbent article (e.g., top sheet, absorbent body, back sheet, etc.) may be referred to simply as the "skin-facing surface" and the "non-skin-facing surface", respectively.

[0023] The absorbent article 1 includes a top sheet 2, an absorbent 3, and a back sheet 4 in this order from the skin-facing side. The top sheet 2 is a liquid-permeable sheet located on the wearer's skin-facing side. The absorbent 3 is a liquid-absorbing and liquid-retentive material located between the top sheet 2 and the back sheet 4. Examples of the absorbent 3 include pulp fiber, synthetic fiber, and absorbent polymer. The back sheet 4 is a liquid-impermeable sheet located on the wearer's non-skin-facing side. Examples of the back sheet 4 include any liquid-impermeable sheet such as a liquid-impermeable nonwoven fabric or synthetic resin film, a composite sheet of these, or an SMS nonwoven fabric. An exterior sheet 9 that reinforces the back sheet 4 and improves the feel may be laminated on the non-skin-facing side of the back sheet 4. Examples of the exterior sheet 9 include any water-repellent sheet such as a material similar to the back sheet 4, a water-repellent nonwoven fabric, a synthetic resin film, or a composite sheet of these. The absorbent 3 is bonded to the top sheet 2 and the back sheet 4 by an adhesive. The adhesive for bonding the top sheet 2, the absorbent body 3 and the back sheet 4 can be a known material that is generally used in absorbent articles 1, such as a thermoplastic adhesive.

[0024] (Surface sheet) The topsheet 2 will be described below with reference to Figs. 2 to 4. The topsheet 2 is made of a nonwoven fabric 10 according to this embodiment. The topsheet 2 has a longitudinal direction L, a width direction W, and a thickness direction T, and has a first side 22 on one side and a second side 24 on the side opposite the first side 22. The first side 22 and the second side 24 each intersect with the thickness direction T. One direction of the thickness direction T is an upward direction, and the other direction is a downward direction.

[0025] The nonwoven fabric 10 has a first fiber layer 26 and a second fiber layer 28 in the above order in the thickness direction T. The first fiber layer 26 is made of thermoplastic resin fibers and has a first surface 22 that becomes the skin-facing surface of the topsheet 2 (liquid-permeable sheet). There are no particular limitations on the nonwoven fabric 10 as long as it is a nonwoven fabric that can be used as a topsheet, but a thermally bonded nonwoven fabric in which thermoplastic resin fibers are thermally bonded to each other is preferable, and an air-through nonwoven fabric is more preferable.

[0026] The second fiber layer 28 contains water-absorbent fibers and thermoplastic resin fibers, and has a second surface 24 that is the non-skin facing surface of the topsheet 2. The second fiber layer 28 preferably contains 30% to 70% by mass, and more preferably 40% to 60% by mass, of water-absorbent fibers. A portion of the water-absorbent fibers may penetrate the first fiber layer 26 and be exposed from the first surface 22.

[0027] The nonwoven fabric 10 may further include a third fiber layer 36 made of thermoplastic resin fibers on the second surface 24 side. That is, the nonwoven fabric 10 may include the first fiber layer 26, the second fiber layer 28, and the third fiber layer 36 in this order in the thickness direction T. The third fiber layer 36 may be made of the same material as the first fiber layer 26. The third fiber layer 36 is in contact with the second fiber layer 28 on the surface facing the skin. When the nonwoven fabric 10 includes the third fiber layer 36, the surface on the non-skin facing side of the third fiber layer 36 becomes the second surface 24, which is the non-skin facing surface of the nonwoven fabric 10.

[0028] The nonwoven fabric 10 has, on the first surface 22, a plurality of solid protrusions 30 that protrude in a direction from the second surface 24 toward the first surface 22, and a plurality of recesses 32 that are recessed in a direction from the first surface 22 toward the second surface 24. In this specification, "solid" means that there is no space in the protrusions 30 where the fiber density is significantly lower than the surroundings, which would prevent the movement of liquid. If the difference in height between the highest part 31, which is the highest part of the first surface 22, and the deepest part 33, which is the lowest part of the first surface 22, is d, the parts that protrude upward from the position at a height of d / 2 from the deepest part 33 can be called protrusions 30, and the parts that are recessed downward can be called recesses 32.

[0029] In the nonwoven fabric 10, the thickness Td1 of the first fiber layer 26 in the recesses 32 is thinner than the thickness Tc1 of the first fiber layer 26 in the protrusions 30. Here, the thickness Td1 of the first fiber layer 26 in the recesses 32 is the thickness of the first fiber layer 26 in the deepest parts 33, and the thickness Tc1 of the first fiber layer 26 in the protrusions 30 is the thickness of the first fiber layer 26 in the highest parts 31.

[0030] The thickness of each portion of the first fiber layer 26 and the second fiber layer 28 of the nonwoven fabric 10 is measured by the following method. First, the hydrophilic fibers are dyed, and then the thickness of each portion is measured. Dyeing of the hydrophilic fibers is performed in the following procedure. (1) Prepare the nonwoven fabric to be measured for thickness. (2) Put 1 L of water in a pot and heat it to 60°C to 70°C. (3) Put the reagent Kayastain Q (Shikisensha Co., Ltd.) into the pot (2) and dissolve it. (4) Heat the pot to 80°C. (5) Put the nonwoven fabric into the pot (4) and leave it for 30 minutes. (5) Then, rinse the nonwoven fabric with running water. (6) Dry in an oven at 80°C for 1 hour. As a result of the above procedure, the absorbent fibers are dyed blue and the thermoplastic resin fibers are dyed yellow.

[0031] The thickness is measured using the following procedure. (1) The dyed nonwoven fabric is cut into a sample with a length of 5 mm in the machine direction (MD) and 20 mm in the cross direction (CD). (2) The sample is fixed to a jig with double-sided tape so that the CD cross section can be observed. (3) An enlarged photograph of the cross section is taken using a Keyence Corporation VHX-7000 digital microscope, the distance between two points for planar measurement is selected, and the thickness of each part of the first fiber layer and second fiber layer of the nonwoven fabric is measured.

[0032] The dimensions of the protrusions 30 can be, for example, 0.25 to 5 mm in width, 0.25 to 5 mm in height, and 0.5 to 10 mm in pitch. The dimensions of the protrusions 30 can be measured from a planar photograph or planar image of the nonwoven fabric 10 in an unpressurized state, observed under magnification using a magnification observation means such as a scanning electron microscope.

[0033] 2, the multiple protrusions 30 are formed as multiple ridges extending continuously in the longitudinal direction L, and the multiple recesses 32 are adjacent to the ribs in the width direction W (i.e., located between adjacent ribs in the width direction W) and are formed as multiple grooves extending continuously in the longitudinal direction L. Because the nonwoven fabric 10 has such a ridge-and-groove structure, it has excellent cushioning properties in the thickness direction T and is comfortable to the touch, and can diffuse excrement along the longitudinal direction L in which the ribs and grooves extend.

[0034] The second surface 24 of the nonwoven fabric 10 has a substantially flat surface structure. The nonwoven fabric 10 can secure a larger contact area with the absorbent 3 arranged on the non-skin facing side of the top sheet 2, and can more efficiently and reliably transfer liquid excrement that permeates the top sheet 2 to the absorbent 3. In the present invention, the second surface 24 of the nonwoven fabric 10 is not limited to the above-mentioned surface structure. For example, the second surface 24 of the nonwoven fabric 10 may have a surface structure in which the convex portions 30 on the first surface 22 side and the portions corresponding to the thickness direction T protrude in a direction from the first surface 22 toward the second surface 24. As another example, the second surface 24 of the nonwoven fabric 10 may have a surface structure in which the convex portions 30 on the first surface 22 side and the portions corresponding to the thickness direction T are recessed in a direction from the second surface 24 toward the first surface.

[0035] The nonwoven fabric 10 may include compressed portions 34 as shown in Fig. 2. The compressed portions 34 are arranged intermittently in the longitudinal direction L in the recesses 32. The compressed portions 34 may be arranged at equal intervals in the longitudinal direction L in the recesses 32, or may be arranged at unequal intervals. In the recesses 32 adjacent to each other in the width direction W, the compressed portions 34 may be located at the same position in the longitudinal direction L, or at different positions. The nonwoven fabric 10 shown in Fig. 2 has compressed portions 34 arranged in a checkerboard pattern in the recesses 32. The compressed portions 34 are formed by sandwiching the first fiber layer 26 from above and the second fiber layer 28 from below in the thickness direction T, and join the first fiber layer 26 and the second fiber layer 28 together.

[0036] The basis weights of the first fiber layer 26 and the second fiber layer 28 are generally uniform in the surface direction. The fiber density of the protruding portions 30 is lower than the fiber density of the recessed portions 32. The fiber density of the recessed portions 32 is lower than the fiber density of the compressed portions 34. The basis weight of the first fiber layer 26 and the basis weight of the second fiber layer 28 may be higher or the same.

[0037] The first fiber layer 26 is liquid permeable and has a basis weight of, for example, 6 to 200 g / m 2 The thermoplastic resin fibers contained in the first fiber layer 26 are not particularly limited as long as they are made of a thermoplastic resin, and examples thereof include known resins such as olefin resins such as polyethylene (PE), polypropylene (PP), and ethylene-vinyl acetate copolymer (EVA); polyester resins such as polyethylene terephthalate (PET) and polylactic acid (PLA); and polyamide resins such as 6-nylon. These resins may be used alone or in combination of two or more types of resins. The structure of such fibers made of thermoplastic resin is not particularly limited, and examples thereof include composite fibers such as core-sheath type fibers such as PET / PE, side-by-side type fibers, and island / sea type fibers; hollow type fibers; and irregular cross-section fibers such as flat, Y-shaped, and C-shaped fibers. Fibers having these structures may be used alone or in combination of two or more types of fibers. The fineness of the fibers is, for example, 1 to 20 dtex.

[0038] The second fiber layer 28 is liquid permeable and has a basis weight of, for example, 6 to 200 g / m 2 Examples of the water-absorbent fibers contained in the second fiber layer 28 include natural cellulosic fibers such as pulp, cotton, and hemp; and regenerated cellulosic fibers such as rayon, lyocell, and cupra. These cellulosic fibers may be used alone or in combination of two or more types of fibers. The thermoplastic resin fibers contained in the second fiber layer 28 can be selected from the thermoplastic resin fibers exemplified in the first fiber layer 26, and may be the same as or different from those in the first fiber layer 26. The fineness of the thermoplastic resin fibers contained in the second fiber layer 28 is, for example, 1 to 20 dtex.

[0039] The fiber diameter of the thermoplastic resin fibers contained in the second fiber layer 28 may be different from the fiber diameter of the thermoplastic resin fibers contained in the first fiber layer 26. The fiber diameter of the thermoplastic resin fibers contained in the second fiber layer 28 may be smaller than the fiber diameter of the thermoplastic resin fibers contained in the first fiber layer 26. Thermoplastic resin fibers with smaller fiber diameters are more likely to be thermally bonded to each other. Therefore, when an air-through nonwoven fabric is formed using thermoplastic resin fibers with smaller fiber diameters, a nonwoven fabric that is less likely to deform can be obtained because it has more thermally bonded joints.

[0040] The content of the water-absorbent fibers in the second fiber layer 28 can be obtained as follows. (1) A sample of the target area is cut out from a nonwoven fabric that has been dried at 105°C for 1 hour, and the initial mass (g) of the sample is measured. (2) The sample is immersed in 70% sulfuric acid for 1 hour to dissolve the water-absorbent fibers. (3) After immersion in sulfuric acid, the sample is washed with about 6 liters of water while being sucked on a Buchner funnel, and then washed with about 1 liter of pure water. (4) The washed sample is dried at 105°C for 2 hours, and the post-treatment mass (g) of the sample is measured. (5) The post-treatment mass of the sample is subtracted from the initial mass of the sample to calculate the water-absorbent fiber content mass (g) in the sample, and the obtained water-absorbent fiber content mass is converted into a mass per unit planar area to obtain the water-absorbent fiber content mass.

[0041] The first fiber layer 26 and the second fiber layer 28 can be bonded by a gas blowing method. Specifically, the method is as follows. A first fiber web made of thermoplastic resin fibers for the first fiber layer 26 and a second fiber web containing water-absorbent fibers and thermoplastic resin fibers for the second fiber layer 28 are stacked to form a laminated fiber web. Next, a gas (e.g., air, etc.) at a predetermined temperature and pressure is blown onto the surface of the laminated fiber web while the laminated fiber web is being transported, thereby entangling the fibers within and between the fiber webs. Next, the laminated fiber web is transported to an air-through type heating device, and the fibers within and between the fiber webs are fused by thermoplastic resin fibers in the heating device, thereby obtaining a nonwoven fabric in which the first fiber layer 26 made of the thermoplastic resin fibers and the second fiber layer 28 containing water-absorbent fibers and thermoplastic resin fibers are bonded together. The second fiber layer 28 contains thermoplastic resin fibers having thermally bonded joints and water-absorbent fibers that are not thermally bonded.

[0042] The method of imparting the above-mentioned uneven structure to the nonwoven fabric obtained by bonding the above-mentioned first fiber layer 26 and second fiber layer 28 can basically be performed according to the composite sheet manufacturing method described in Japanese Patent No. 6139039. Specifically, the nonwoven fabric obtained by bonding the first fiber layer 26 made of thermoplastic resin fibers and the second fiber layer 28 containing water-absorbent fibers and thermoplastic resin fibers is sandwiched between a pair of gear processing rolls and locally pressed to form multiple recesses 32, thereby obtaining the nonwoven fabric 10.

[0043] The nonwoven fabric 10 including the first fiber layer 26, the second fiber layer 28, and the third fiber layer 36 can be formed by the following method. A third fiber web made of thermoplastic resin fibers for the third fiber layer 36 is layered on the first fiber web and the second fiber web to form a laminated fiber web. As described above, the laminated fiber web is entangled with the fibers in each fiber web and between each fiber web by blowing a gas (e.g., air, etc.) at a predetermined temperature and pressure onto the surface of the laminated fiber web while being conveyed. Next, the laminated fiber web is conveyed to an air-through type heating device, and the fibers in each fiber web and between each fiber web are fused with thermoplastic resin fibers in the heating device, thereby obtaining a nonwoven fabric in which the first fiber layer 26, the second fiber layer 28, and the third fiber layer 36 are joined together. Furthermore, a plurality of recesses 32 are formed by the above-mentioned gear processing, and the nonwoven fabric 10 can be obtained.

[0044] Next, the characteristics of the nonwoven fabric 10 subjected to a load in the thickness direction T will be described. The load in the thickness direction T on the nonwoven fabric 10 acts mainly on the protrusions 30 protruding in the thickness direction T. The protrusions 30 are compressed in the thickness direction T by the load, and as the load increases, the difference d between the highest part 31 of the protrusion 30 and the deepest part 33 of the recess 32 gradually decreases. In the nonwoven fabric 10 to which no load is applied in the thickness direction T, the thickness of the first fiber layer 26 at the protrusion 30 is Tc1, and the thickness of the first fiber layer 26 at the recess 32 is Td1. The compressive strength of the nonwoven fabric 10 in the thickness direction T is 2.9 kPa (30 gf / cm 2 In the nonwoven fabric 10 to which a load of 2.9 kPa (30 gf / cm) is applied, the thickness of the first fiber layer 26 in the protruding portions 30 is defined as Tc2, and the thickness of the first fiber layer 26 in the recessed portions 32 is defined as Td2. 2 ) is intended to represent the load that is applied to the sanitary napkin when the wearer puts the sanitary napkin on.

[0045] Since the concave portion 32 is formed in the nonwoven fabric 10 by gear processing or the like as described above, the first fiber layer 26 in the concave portion 32 is compressed in the thickness direction T as compared with the convex portion 30. Therefore, in the nonwoven fabric 10 to which no load is applied in the thickness direction T, the thickness Tc1 of the first fiber layer 26 in the convex portion 30 is thicker than the thickness Td1 of the first fiber layer 26 in the concave portion 32. That is, the nonwoven fabric 10 to which no load is applied in the thickness direction T satisfies the relational expression of Tc1 > Td1.

[0046] When a load of 2.9 kPa (30 gf / cm 2 ) is applied to the nonwoven fabric 10 in the thickness direction T, the nonwoven fabric 10 satisfies the relational expression of (Tc2 / Tc1) < (Td2 / Td1). That is, in the nonwoven fabric 10 to which a load of 2.9 kPa is applied in the thickness direction T, the first fiber layer 26 in the convex portion 30 of the nonwoven fabric 10 has a higher rate of decrease in thickness than the first fiber layer 26 in the concave portion 32. In the case of the nonwoven fabric 10 having the squeezing portion 34, the thickness of the first fiber layer 26 in the concave portion 32 is the thickness measured in the concave portion 32 other than the squeezing portion 34.

[0047] In the nonwoven fabric 10 to which a load of 2.9 kPa is applied in the thickness direction T, it is preferable that the thickness Tc2 of the first fiber layer 26 in the convex portion 30 is thinner than the thickness Td2 of the first fiber layer 26 in the concave portion 32. That is, it is preferable that the nonwoven fabric 10 satisfies the relational expression of Tc2 < Td2. As described above, the nonwoven fabric 10 to which no load is applied in the thickness direction T satisfies the relational expression of Tc1 > Td1, but the first fiber layer 26 in the convex portion 30 is compressed by receiving the load in the thickness direction T. As a result, in the nonwoven fabric 10 to which a load of 2.9 kPa is applied in the thickness direction T, the nonwoven fabric 10 satisfies the relational expression of Tc2 < Td2. In the case of the nonwoven fabric 10 having the squeezing portion 34, the thickness of the first fiber layer 26 in the concave portion 32 is the thickness measured in the concave portion 32 other than the squeezing portion 34.

[0048] In nonwoven fabric 10 to which a load of 2.9 kPa is applied in the thickness direction T, it is preferable that deepest parts 33 of recesses 32 are recessed from highest parts 31 of protrusions 30 toward the first surface 22 to the second surface 24. When exposed to a load in the thickness direction T, protrusions 30 are compressed, and the greater the load, the smaller the difference between highest parts 31 of protrusions 30 and deepest parts 33 of recesses 32 becomes. When the load in the thickness direction T is 2.9 kPa or less, nonwoven fabric 10 maintains a shape in which deepest parts 33 of recesses 32 are recessed from highest parts 31 of protrusions 30 toward the first surface 22 to the second surface 24.

[0049] (Measurement method) The basis weight, thickness, fiber density and fineness of the nonwoven fabric in the above embodiment are measured by the following methods. (1) Basis weight of nonwoven fabric: A nonwoven fabric is cut into a size of 5 cm x 5 cm to prepare a sample, which is then dried in an atmosphere of 100°C or higher and its mass is measured. The measured mass is divided by the area of ​​the sample to calculate the basis weight of the sample. The average value of the basis weights of the 10 samples is regarded as the basis weight of the nonwoven fabric. (2) Thickness of nonwoven fabric: 15cm 2 A thickness gauge with a gauge head of 3 gf / cm (model FS-60DS, manufactured by Daiei Chemical Industry Co., Ltd.) was used. 2 The thickness of the nonwoven fabric is measured under the condition of a measurement load of 0.3 kPa. The thickness is measured at three points on one sample, and the average value of the three thicknesses is regarded as the thickness of the nonwoven fabric. (3) Fiber density of nonwoven fabric: The fiber density of the nonwoven fabric is calculated by dividing the weight of the nonwoven fabric determined by the above method by the thickness of the nonwoven fabric determined by the above method. (4) Fiber fineness: The fiber fineness is determined by measuring the cross-sectional area of ​​the fiber by magnifying the cross-sectional shape of the fiber using a scanning electron microscope, and calculating the fiber fineness from the cross-sectional area and the specific gravity of the fiber (i.e., the specific gravity of the components that make up the fiber).

[0050] (Action and Effects) When the nonwoven fabric 10 is worn, the convex portions 30 come into contact with the wearer's skin, and the concave portions 32 are spaced from the wearer's skin by a maximum distance equal to the height from the deepest portion 33 to the highest portion 31. When liquid excrement such as menstrual blood is supplied from the wearer, the first fiber layer 26 (thermoplastic resin fiber) of the convex portions 30 receives the excrement and quickly transfers the excrement through the second fiber layer 28 to the absorbent body 3 located on the non-skin-facing surface (second surface 24) side.

[0051] In addition to liquid excrement, moisture such as sweat is discharged from the wearer's skin. Unlike excrement, the moisture is in the form of water droplets or steam. In the protrusions 30, the first fiber layer 26 made of thermoplastic resin fibers is thick, so that the moisture, unlike excrement, reaches the recesses 32 mainly from the wearer's skin directly or along the first surface 22 rather than migrating through the first fiber layer 26 in the thickness direction T. In the recesses 32, the thickness of the first fiber layer 26 is thinner than that of the first fiber layer 26 of the protrusions 30, so that the distance from the first surface 22 to the second fiber layer 28 in the recesses 32 is shorter than the distance from the first surface 22 to the second fiber layer 28 in the protrusions 30, and moisture such as sweat easily reaches the second fiber layer 28 in the recesses 32. Therefore, in the nonwoven fabric 10, the absorbent fibers contained in the second fiber layer 28 of the recesses 32 easily absorb moisture such as sweat discharged from the wearer's skin. Furthermore, the moisture that reaches the second fiber layer is transferred by the thermoplastic resin fibers contained in the second fiber layer to the absorbent body 3 located on the non-skin facing surface (second surface 24) side.

[0052] When nonwoven fabric 10 is subjected to a load in the thickness direction T, i.e., when it is subjected to the body pressure of the wearer, protrusions 30 protruding in the thickness direction T are sandwiched between the wearer's skin and the wearer's underwear, etc., and the load acts mainly on protrusions 30. Therefore, protrusions 30 are compressed in the thickness direction T by the load, and the greater the load in the thickness direction T, the smaller the difference d between the highest part 31 of protrusion 30 and the deepest part 33 of recess 32 becomes.

[0053] When a load of 2.9 kPa is applied in the thickness direction T, the nonwoven fabric 10 satisfies the relational expression (Tc2 / Tc1)<(Td2 / Td1). That is, in the nonwoven fabric 10, the first fiber layer 26 in the convex portions 30 is reduced in thickness at a higher rate than the first fiber layer 26 in the concave portions 32. Therefore, when the nonwoven fabric 10 is subjected to the body pressure of the wearer, the distance from the first surface 22 to the second fiber layer 28 is also shorter in the convex portions 30 than before the load in the thickness direction T is applied, and moisture such as sweat discharged from the wearer's skin is more likely to reach the second fiber layer 28 through the first fiber layer 26 in the convex portions 30. A part of the moisture is absorbed by the water-absorbent fibers contained in the second fiber layer 28, and the other part is transferred to the absorbent body 3 located on the non-skin-facing surface (second surface 24) side by the thermoplastic resin fibers contained in the second fiber layer 28. Therefore, when nonwoven fabric 10 is subjected to the body pressure of the wearer, the water-absorbent fibers in protruding portions 30 can absorb moisture such as sweat discharged from the wearer's skin.

[0054] Even when the second fiber layer 28 absorbs moisture such as sweat of the wearer and excrement excreted by the wearer as described above, the first fiber layer 26 in the protrusions 30 interposes the absorbent fibers contained in the second fiber layer 28 between the wearer's skin and the second fiber layer 28, and in the recesses 32, the first fiber layer 26 of the protrusions 30 holds the absorbent fibers contained in the second fiber layer 28 at a position away from the wearer's skin. Therefore, the nonwoven fabric 10 prevents the first surface 22 from sticking to the wearer's skin.

[0055] As described above, the nonwoven fabric 10 has excellent water absorbency and can be used as a liquid-permeable sheet for the absorbent article 1 that is prevented from sticking to the skin of the wearer.

[0056] In a preferred embodiment, in the protrusions 30 of the nonwoven fabric 10, the basis weights of the first fiber layer 26 and the second fiber layer 28 are uniform in the surface direction, and the thickness of the first fiber layer 26 in the recesses 32 is thinner than the thickness of the first fiber layer 26 in the protrusions 30, i.e., the thickness of the first fiber layer 26 in the protrusions 30 is thicker than the thickness of the first fiber layer 26 in the recesses 32. In this case, the fiber density of the first fiber layer 26 in the protrusions 30 is lower than that of the first fiber layer 26 in the recesses 32, and the first fiber layer 26 is more likely to deform in the thickness direction T. Furthermore, when the protrusions 30 are subjected to a load in the thickness direction T, the load in the thickness direction T acts from the first surface 22 and the second surface 24, so that the thickness of the first fiber layer 26 in the protrusions 30 is more likely to decrease than that of the first fiber layer 26 in the recesses 32. On the other hand, in the recesses 32, the basis weights of the first fiber layer 26 and the second fiber layer 28 are uniform in the surface direction, and the thickness of the first fiber layer 26 in the recesses 32 is thinner than the thickness of the first fiber layer 26 in the protrusions 30. Therefore, the fiber density of the first fiber layer 26 in the recesses 32 is high, and the first fiber layer 26 is less likely to deform in the thickness direction T. Furthermore, as long as the protrusions 30 protrude in the thickness direction T beyond the recesses 32 on the first surface 22, the nonwoven fabric 10 is hardly subjected to a load in the thickness direction T on the recesses 32. Therefore, even when a load is applied in the thickness direction T, the thickness of the first fiber layer 26 in the recesses 32 is less likely to change than the thickness of the first fiber layer 26 in the protrusions 30.

[0057] In a preferred embodiment, in a state where no load is applied in the thickness direction T, the thickness Tc1 of the first fiber layer 26 in the convex portion 30 is greater than the thickness Td1 of the first fiber layer 26 in the concave portion 32. That is, the nonwoven fabric 10 in a state where no load is applied in the thickness direction T satisfies the relational expression Tc1 > Td1. In this case, when a load is applied to the nonwoven fabric 10 in the thickness direction T, the first fiber layer 26 in the convex portion 30 has a higher rate of decrease in thickness than the first fiber layer 26 in the concave portion 32. As a result, the difference in thickness between the first fiber layer 26 in the convex portion 30 and the first fiber layer 26 in the concave portion 32 is reduced. As a result, in the nonwoven fabric 10 to which a load of 2.9 kPa is applied in the thickness direction T, the nonwoven fabric 10 satisfies the relational expression Tc2 < Td2. In this way, when the load in the thickness direction T is 2.9 kPa, the thickness of the first fiber layer 26 in the convex portion 30 decreases, and the thickness of the first fiber layer 26 in the convex portion 30 becomes thinner than the thickness of the first fiber layer 26 in the concave portion 32. As a result, the distance from the first surface 22 to the second fiber layer 28 also becomes closer in the convex portion 30. Therefore, when the nonwoven fabric 10 receives the body pressure of the wearer or the like, the water-absorbing fibers can also absorb moisture such as sweat discharged from the wearer's skin in the convex portion 30.

[0058] When the nonwoven fabric 10 receives the body pressure of the wearer or the like, the convex portion 30 is deformed in the thickness direction T while receiving the above load. The convex portion 30 is compressed in the thickness direction T by the load, and the difference d between the highest portion 31 of the convex portion 30 and the deepest portion 33 of the concave portion 32 is reduced. When a load of 2.9 kPa is applied to the nonwoven fabric 10 in the thickness direction T, in a preferred embodiment, the nonwoven fabric 10 maintains a shape in which the deepest portions 33 of the plurality of concave portions 32 are recessed toward the second surface 24 from the highest portions 31 of the plurality of convex portions 30. That is, when the load in the thickness direction T of the nonwoven fabric 10 is 2.9 kPa or less, the nonwoven fabric 10 maintains a shape in which the deepest portion 33 of the concave portion 32 is recessed from the highest portion 31 of the convex portion 30 toward the second surface 24 from the first surface 22. In this case, when the nonwoven fabric 10 receives the body pressure of the wearer or the like, the nonwoven fabric 10 suppresses the sticking to the wearer's skin by preventing the concave portion 32 from touching the wearer's skin.

[0059] In a preferred embodiment, the nonwoven fabric 10 contains 30% to 70% by mass of absorbent fibers in the second fiber layer 28. In this case, moisture such as sweat is easily absorbed in the recesses 32, and also in the protrusions 30, the distance from the first surface 22 to the second fiber layer 28 becomes short when the nonwoven fabric 10 is loaded in the thickness direction T, so that moisture such as sweat is easily absorbed. Since the nonwoven fabric 10 contains thermoplastic resin fibers in the second fiber layer 28, the excrement received by the first fiber layer 26 in the protrusions 30 is quickly transferred to the absorbent body 3 arranged on the non-skin-facing side, and the excrement that arrives along the first surface 22 in the recesses 32 is transferred to the absorbent body 3 on the non-skin-facing side. Therefore, since the nonwoven fabric 10 contains 30% to 70% by mass of absorbent fibers and thermoplastic resin fibers, moisture such as sweat discharged from the wearer's skin is absorbed by the absorbent fibers, while the excrement discharged from the wearer is transferred to the non-skin-facing side by the thermoplastic resin fibers.

[0060] In a preferred embodiment, the fiber diameter of the thermoplastic resin fiber of the second fiber layer 28 is smaller than that of the thermoplastic resin fiber of the first fiber layer 26. In this case, the second fiber layer 28 has more joints where the intersections of the thermoplastic resin fibers are thermally bonded than the first fiber layer 26 because the fiber diameter is smaller. That is, the second fiber layer 28 is less likely to deform because of the larger joints. On the other hand, the first fiber layer 26 is more difficult to thermally bond than the thermoplastic resin fiber of the second fiber layer 28 because the fiber diameter is larger, and has fewer joints where the intersections of the thermoplastic resin fibers are thermally bonded, so it is more likely to deform. Therefore, in the present nonwoven fabric 10, the first fiber layer 26, which is easily deformed, is supported from the second surface 24 side by the second fiber layer 28, which is less likely to deform, when a load is applied in the thickness direction T, the thickness of the protrusions 30 is reduced, and the distance from the first surface 22 to the second fiber layer 28 is also likely to be shortened in the protrusions 30. As a result, since the fiber diameter of the thermoplastic resin fibers in the second fiber layer 28 of the nonwoven fabric 10 is smaller than the fiber diameter of the thermoplastic resin fibers in the first fiber layer 26, when the nonwoven fabric 10 is subjected to the wearer's body pressure, the absorbent fibers are more likely to absorb moisture such as sweat discharged from the wearer's skin.

[0061] In a preferred embodiment, the nonwoven fabric 10 includes a third fiber layer 36 on the second surface 24 side. In this case, when the nonwoven fabric 10 is subjected to the body pressure of the wearer, the second fiber layer 28 and the third fiber layer 36 support the first fiber layer 26 at the protrusions 30 from the second surface 24 side. In this case, when a load is applied to the nonwoven fabric 10 in the thickness direction T, the load is likely to be applied to the first fiber layer 26 at the protrusions 30, and the thickness of the first fiber layer 26 at the protrusions 30 is likely to decrease. Therefore, when the nonwoven fabric 10 is subjected to the body pressure of the wearer, the thickness of the first fiber layer 26 at the protrusions 30 decreases, and the distance from the first surface 22 to the second fiber layer 28 at the protrusions 30 also becomes shorter, and the absorbent fibers can absorb moisture such as sweat discharged from the wearer's skin.

[0062] In a preferred embodiment, the nonwoven fabric 10 has a portion of the absorbent fiber exposed from the first surface 22. In this case, when the nonwoven fabric 2 is used as a liquid-permeable sheet of the absorbent article 1, moisture such as sweat discharged from the wearer's skin is easily transferred to the second fiber layer 28 through the portion of the absorbent fiber exposed from the skin-facing surface (first surface 22), and therefore the nonwoven fabric 2 has excellent water absorbency.

[0063] (Modification) The types and uses of absorbent articles are not particularly limited, and examples thereof include hygiene and sanitary products such as panty liners, disposable diapers (tape type, pants type), incontinence pads, sweat absorbing sheets, etc., which may be intended for humans or non-human animals such as pets. The liquids that the absorbent articles are intended to absorb are not particularly limited, and examples thereof include liquid excrement, body fluids, etc., of the wearer.

[0064] The uneven structure having a plurality of convex portions and a plurality of concave portions is not limited to a ridge-furrow structure, and examples thereof include an uneven structure consisting of a plurality of rows of convex portions extending intermittently in the longitudinal direction and aligned in the width direction, and a plurality of rows of concave portions extending intermittently in the longitudinal direction between adjacent convex portions in the width direction, and an uneven structure consisting of a plurality of hemispherical or cylindrical convex portions and a plurality of concave portions located between adjacent convex portions.

[0065] Although the case where the third fiber web is overlaid on the first fiber web and the second fiber web to form a laminated fiber web has been described as an example of forming the nonwoven fabric 10 including the first fiber layer 26, the second fiber layer 28, and the third fiber layer 36, the present invention is not limited to this. For example, the nonwoven fabric may include a first nonwoven fabric having a ridge-and-groove structure on the skin-facing surface formed by bonding the first fiber layer 26 and the second fiber layer 28, and a second nonwoven fabric consisting of the third fiber layer 36 on the non-skin-facing surface side of the first nonwoven fabric.

[0066] (Example) Nonwoven fabrics corresponding to the above-described embodiments were produced and evaluated. The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0067] (1) Sample By the above-mentioned gear processing, an example nonwoven fabric was produced, which is an air-through nonwoven fabric in which a first fiber layer made of thermoplastic resin fiber of sheath-core type fiber and a second fiber layer containing rayon as a water-absorbent fiber and thermoplastic resin fiber of sheath-core type fiber are bonded together. The detailed configuration of the nonwoven fabric according to the example is as shown in Table 1. The nonwoven fabric of the example had a plurality of ridges and a plurality of grooves.

[0068] As reference examples, an air-through nonwoven fabric formed of thermoplastic resin fibers of a core-sheath type fiber (Reference Example 1) and a nonwoven fabric made of cotton (Reference Example 2) were produced. The detailed configurations of the nonwoven fabrics of Reference Examples 1 and 2 are as shown in Table 1. Neither of the nonwoven fabrics of Reference Examples 1 and 2 had ridges or grooves on the surface.

[0069] (2) Evaluation method The adhesion of the nonwoven fabric was evaluated by the following method. (i) A solution of 50 ml of ion-exchanged water and 50 ml of colored water was prepared. (ii) 8 g of the above solution was added dropwise to Silcot (trademark) (manufactured by Unicharm Corporation) while measuring the amount added, so that the solution was completely absorbed. (iii) 30g / cm with artificial leather attached onto Silcot 2 A weight (size: 50 mm x 35 mm) was placed on the sample and left for 30 seconds. (iv) A sample cut to a size of 60 mm x 50 mm was placed on two layers of airlaid nonwoven fabric, and the weight (iii) was placed on the sample. (v) After 30 seconds, the weight was lifted and visually inspected to see if the sample was attached to the weight. The above evaluation was carried out for each sample with N=10. The weight (iii) above was transferred onto filter paper for 30 seconds, and the amount of solution adhering to the artificial leather of the weight was measured, yielding 0.036 g (average of N=5). When the number of samples that stuck to the weight (N=10) was two or less, it was judged as passed, and when it was three or more, it was judged as failed.

[0070] (3) Results The nonwoven fabric according to the embodiment passed the test with two samples sticking to the weight, and one of the samples immediately fell off the weight due to its own weight. The nonwoven fabric according to the reference example failed the test with 10 samples sticking to the weight. From the above, it was confirmed that the nonwoven fabric according to the embodiment can suppress sticking to the wearer's skin.

[0071] [Table 1] [Explanation of symbols]

[0072] 1. Absorbent articles 1A Main unit 1B Flap section 2 Surface sheet 3. Absorber 4 Back sheet 9 Exterior Sheet 10. Nonwoven Fabrics 22 Page 1 24 Side 2 26 First fiber layer 28 Second fiber layer 30 Convex 31 Highest point 32 Recess 33 The Deepest Part 34 Pressing section

Claims

1. A nonwoven fabric for a liquid-permeable sheet of an absorbent article, the nonwoven fabric comprising a first fiber layer and a second fiber layer in that order in a thickness direction, the first fiber layer is made of thermoplastic resin fibers and has a first surface that is a skin-facing surface of the liquid-permeable sheet; the second fiber layer includes water-absorbent fibers and thermoplastic resin fibers, and has a second surface that is a non-skin facing surface of the liquid-permeable sheet; the first surface has a plurality of solid protruding portions protruding in a direction from the second surface toward the first surface, and a plurality of recessed portions recessed in a direction from the first surface toward the second surface, a thickness of the first fiber layer in the recessed portions is smaller than a thickness of the first fiber layer in the protruding portions; In the nonwoven fabric to which no load is applied in the thickness direction, the thickness of the first fiber layer at the plurality of convex portions and the thickness of the first fiber layer at the plurality of concave portions are defined as Tc1 and Td1, respectively, and in the nonwoven fabric to which a load of 2.9 kPa is applied in the thickness direction, the thickness of the first fiber layer at the plurality of convex portions and the thickness of the first fiber layer at the plurality of concave portions are defined as Tc2 and Td2, respectively, satisfying the relational expression (Tc2 / Tc1)<(Td2 / Td1), The basis weight of each of the first fiber layer and the second fiber layer is uniform in a surface direction, A nonwoven fabric in which, when a load of 2.9 kPa is applied in the thickness direction, the thickness of the first fiber layer in the multiple convex portions is thinner than the thickness of the first fiber layer in the multiple concave portions.

2. 2. The nonwoven fabric according to claim 1, wherein in the nonwoven fabric to which a load of 2.9 kPa is applied in the thickness direction, the deepest portions of the plurality of recesses are located at a position recessed from the first surface toward the second surface relative to the highest portions of the plurality of protrusions.

3. The nonwoven fabric according to claim 1 or 2, wherein the second fiber layer contains 30% by mass to 70% by mass of the water-absorbent fiber.

4. a fiber diameter of the thermoplastic resin fiber of the second fiber layer is smaller than a fiber diameter of the thermoplastic resin fiber of the first fiber layer; 4. The nonwoven fabric according to claim 1, wherein in each of the first fiber layer and the second fiber layer, intersections of the thermoplastic resin fibers are thermally bonded.

5. The nonwoven fabric according to any one of claims 1 to 4, further comprising a third layer made of thermoplastic resin fibers on the second surface side.

6. The nonwoven fabric according to any one of claims 1 to 5, wherein a portion of the water-absorbent fibers is exposed from the first surface.

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