Nonwoven fabric for absorbent article

Abstract

To provide a nonwoven fabric for absorbent article capable of achieving excellent cushioning property and liquid permeability.SOLUTION: A nonwoven fabric has a first fiber layer and a second fiber layer stacked in a thickness direction and includes fiber fused parts at intersections between fibers. The first fiber layer and the second fiber layer are integrated by the fiber fused parts of fibers of each other. The first fiber layer has an uneven structure having a plurality of convex parts and bottom parts disposed between adjacent convex parts. Each of the plurality of convex parts has an apex and a wall part supporting the apex. The wall part extends perpendicular to a plane direction of the nonwoven fabric. An aperture penetrating in the thickness direction is disposed on the bottom part. The nonwoven fabric for absorbent article has the second fiber layer on a side where the bottom parts of the first fiber layer exist. Fibers constituting the second fiber layer have fiber diameter smaller than that of fibers constituting the first fiber layer and are exposed to the first fiber layer side at the aperture.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a nonwoven fabric for absorbent articles. [Background technology]

[0002] Nonwoven fabrics are used in a variety of applications, such as components of absorbent articles such as diapers and sanitary napkins, and come in a variety of structures. For example, Patent Document 1 describes a nonwoven fabric having a concave-convex structure with a plurality of ridges and a bottom, and with an opening at the bottom, as a surface sheet of an absorbent article. Patent Document 2 describes a nonwoven fabric in which a first nonwoven fabric layer and a second nonwoven fabric layer are laminated. The first nonwoven fabric layer has a concave-convex structure, and the second nonwoven fabric layer has a substantially flat shape. Patent Document 3 describes a nonwoven fabric consisting of upper and lower fiber layers as a surface sheet of an absorbent article, and the upper layer has a plurality of convex portions protruding toward the skin contact surface side. The convex portions are dome-shaped with rounded tops and gentle sides from the side walls to the bottoms of the convex portions. The concave portions between the convex portions are formed by embossing, and the upper fiber layer and the lower fiber layer are joined at the concave portions. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-467 A [Patent Document 2] JP 2019-44293 A [Patent Document 3] JP 2009-172354 A Summary of the Invention [Problem to be solved by the invention]

[0004] The nonwoven fabrics described in Patent Documents 1 and 2 have their protrusion tops supported by vertical walls, and therefore have superior cushioning properties compared to the nonwoven fabric described in Patent Document 3, in which the protrusions have gentle wall angles. Furthermore, when the nonwoven fabric described in Patent Document 1 is used as a top sheet or the like of an absorbent article, it allows excreted liquid to flow down along the walls and quickly permeate through the bottom openings to the lower layer. This gives the nonwoven fabric described in Patent Document 1 superior liquid permeability in the thickness direction, and can enhance the liquid absorbency of the absorbent article. However, when the nonwoven fabric described in Patent Document 1 is used as a top sheet and joined to an underlying member, a hot melt adhesive or the like is generally used, and the adhesive is easily exposed to the openings. The presence of the adhesive exposed to the surface through the openings may affect the liquid absorbency. In addition, during the joining, the vertical wall around the openings is joined to the underlying member, so the structure of the wall is easily destroyed, making it difficult to obtain sufficient joining strength. Therefore, there is room for further improvement in this nonwoven fabric from the viewpoint of ensuring the cushioning and liquid permeability described above even when incorporated into an absorbent article. In this regard, in the nonwoven fabric described in Patent Document 3, the convex portions have a gentle wall angle, which makes them less likely to collapse during the above-mentioned bonding. However, the gentle wall angle of the convex portions, coupled with the absence of holes, makes it easy for liquid (e.g., urine in absorbent articles and loose stool with flowability) to flow over the surface. In addition, in the nonwoven fabrics described in Patent Documents 2 and 3, which have no holes and are made of two layers, it is easy to ensure the bonding area between the upper and lower layers and to maintain the structure of the convex portions. However, it cannot be said that the liquid permeation speed and the ability to prevent liquid from remaining are sufficient, and further improvement is desired. As described above, it has been difficult to improve both cushioning properties and liquid permeability in conventional nonwoven fabrics.

[0005] In view of the above, the present invention relates to a nonwoven fabric for absorbent articles which can have both excellent cushioning properties and liquid permeability. [Means for solving the problem]

[0006] The present invention provides a nonwoven fabric for absorbent articles, which has a first fiber layer and a second fiber layer laminated in the thickness direction and includes fiber fusion portions at intersections between fibers, the first fiber layer and the second fiber layer being integrated by the fiber fusion portions between the fibers of each other, the first fiber layer having an uneven structure including a plurality of protrusions and a bottom portion provided between adjacent protrusions, each of the plurality of protrusions having an apex and a wall portion supporting the apex, the wall portion extending perpendicularly to a planar direction of the nonwoven fabric, the bottom portion having an opening portion penetrating through in the thickness direction, the second fiber layer being located on the side of the first fiber layer where the bottom portion is located, and the constituent fibers of the second fiber layer have a smaller fiber diameter than the constituent fibers of the first fiber layer and are exposed to the side of the first fiber layer at the opening portion.

[0007] The present invention also provides a method for producing a nonwoven fabric for absorbent articles, comprising: a pushing step of placing a first fibrous web on a support having an uneven shape with a plurality of protrusions and recesses between the protrusions, and pushing the first fibrous web along the recesses with a pushing part of a pushing member to form a porous fibrous web having an open surface on the opposite side to the support, and a step of blowing a first hot air onto the porous fibrous web after removing the pushing member from the support to fuse the fibers together and obtain a porous nonwoven fabric, a step of supplying a second fibrous web having constituent fibers smaller in fiber diameter than the first fibrous web and laminating it on the open surface side of the porous nonwoven fabric, and a heat fusing step of blowing a second hot air to fuse the fibers of the porous nonwoven fabric and the second fibrous web together and to fuse the fibers in the second fibrous web together. Effect of the Invention

[0008] The nonwoven fabric for absorbent articles of the present invention can have excellent cushioning properties and liquid permeability. According to the manufacturing method of the nonwoven fabric for absorbent articles of the present invention, the nonwoven fabric for absorbent articles of the present invention can be suitably manufactured. [Brief description of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view showing a schematic diagram of a preferred embodiment of a nonwoven fabric for absorbent articles according to the present invention. [Diagram 2] FIG. 1A is an explanatory diagram showing a schematic diagram of the relationship between the uneven structure of the first fiber layer and the liquid surface flow when the nonwoven fabric for absorbent articles of the present embodiment shown in FIG. 1 is inclined to fit the wearer's body as a component of the absorbent article, and FIG. 1B is a cross-sectional diagram showing a schematic diagram of a nonwoven fabric for absorbent articles with a conventional uneven structure when the nonwoven fabric for absorbent articles is inclined to fit the wearer's body as a component of the absorbent article. [Diagram 3] 4 is a photograph in lieu of a drawing showing an example of a protrusion of a second fiber layer penetrating into a first fiber layer through an opening in the nonwoven fabric for absorbent articles of the present embodiment. [Figure 4] 1 is a plan view showing a specific example of a nonwoven fabric for absorbent articles according to the present embodiment, viewed from one side. [Diagram 5] 5 is a cross-sectional view taken along the line R1-R1 of the nonwoven fabric for absorbent articles shown in FIG. 4. [Figure 6] 5 is a cross-sectional view taken along the line R2-R2 of the nonwoven fabric for absorbent articles shown in FIG. 4. [Figure 7] 5 is a cross-sectional view taken along the line R3-R3 of the nonwoven fabric for absorbent articles shown in FIG. 4. [Figure 8] FIG. 1 is an explanatory diagram showing a schematic diagram of a preferred embodiment of the method for manufacturing a nonwoven fabric for absorbent articles according to the present invention, in which (A) shows a pushing process, (B) shows a process for obtaining an porous nonwoven fabric by a first hot air, (C) shows a process for laminating a second fibrous web onto the porous nonwoven fabric, and (D) shows a process for integrating the porous nonwoven fabric and the second fibrous web by a second hot air to form the second fibrous web into a nonwoven fabric. [Figure 9] FIG. [Figure 10] FIG. [Figure 11] FIG. 13 is a plan view showing a state in which the support body and the push-in member are combined. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] A preferred embodiment of the nonwoven fabric for absorbent articles according to the present invention will be described below with reference to the drawings. In this specification, the nonwoven fabric for absorbent articles may be simply referred to as a nonwoven fabric. The nonwoven fabric 10 of this embodiment is a so-called thermal bonded nonwoven fabric having fiber fusion parts at the intersections of the fibers. For example, an air-through nonwoven fabric in which the fiber fusion parts are formed by an air-through method can be mentioned. Therefore, the nonwoven fabric 10 contains thermoplastic fibers as its constituent fibers. That is, the first fiber layer M1 and the second fiber layer M2, which constitute the nonwoven fabric 10, described below, contain thermoplastic fibers as their constituent fibers, and are nonwoven fabrics in which the fiber fusion parts are formed. The first fiber layer M1 and the second fiber layer M2 are integrated by the fiber fusion parts at the intersections of the fibers of each other.

[0011] The nonwoven fabric 10 of this embodiment has a first fiber layer M1 and a second fiber layer M2 laminated in the thickness direction Z as shown in FIG. 1. The nonwoven fabric 10 has a front and back surface, i.e., one side 10T and the other side 10B, with the first fiber layer M1 arranged on the one side 10T and the second fiber layer M2 arranged on the other side 10B. In the nonwoven fabric 10, for example, the one side 10T can be used as the surface. When the nonwoven fabric 10 is used as a member on the skin side of the absorbent body of an absorbent article, for example, as a top sheet, the one side 10T can be used as the skin side. In this case, the first fiber layer M1 is also referred to as the upper layer, and the second fiber layer M2 is also referred to as the lower layer. The one side 10T and the other side 10B refer to the front and back surfaces of the entire nonwoven fabric 10, and also refer to the front and back surfaces of the first fiber layer M1 and the second fiber layer M2. The thickness direction Z of the nonwoven fabric 10 also means the thickness direction Z of each of the first fiber layer M1 and the second fiber layer M2.

[0012] The first fiber layer M1 has a plurality of protruding portions 1 protruding toward one surface side 10T and a bottom portion 2 provided between adjacent protruding portions 1, 1. This gives the first fiber layer M1 an uneven structure in the thickness direction Z. The protruding portions 1 are three-dimensional fiber layers standing in the thickness direction Z of the first fiber layer M1, and are located higher on the one surface side 10T than the bottom portion 2. Each of the plurality of protruding portions 1 has an apex 1A and a wall portion 1B supporting the apex 1A.

[0013] The outer shape of one surface side 10T of top 1A may be a flat surface or a curved surface. From the viewpoint of making it easier to recognize the depth of the unevenness and making the shadows around openings 3 in bottom 2, which will be described later, more clear, it is preferable that one surface side 10T of top 1A is a flat surface.

[0014] A portion of the other surface side 10B of the wall portion 1B (also referred to as a root portion 1D) abuts against the second fiber layer M2. In a contact region 4 between the root portion 1D of the wall portion 1B and the second fiber layer M2, the root portion 1D of the wall portion 1B is embedded in and integrated (fixed) with the second fiber layer M2. This integration can be achieved by various bonding forms. From the viewpoint of increasing the bonding strength and maintaining the uneven shape of the first fiber layer M1, it is preferable that the root portion 1D of the wall portion 1B and the second fiber layer M2 are integrated by a fiber fusion portion at an intersection between the constituent fibers of the root portion 1D of the wall portion 1B and the constituent fibers of the second fiber layer M2.

[0015] The fibers of the wall 1B are preferably oriented longitudinally with respect to the planar direction of the nonwoven fabric 10. The planar direction of the nonwoven fabric 10 referred to here means the direction along a plane (e.g., a flat base) that contacts the surface of the other side 10B of the nonwoven fabric 10 (second fiber layer M2). The longitudinal orientation of the fibers enhances the support force of the wall portion 1B in the thickness direction Z relative to the top portion 1A and the second fiber layer M2, softly absorbing the load, and making it easier for the thickness of the protrusion 1 to be maintained even under the load. It also enhances the thickness recovery of the protrusion 1 when the load is removed. As a result, the nonwoven fabric 10 including the first fiber layer M1 and the second fiber layer M2, coupled with the elasticity due to the fiber structure of the fiber layers, is easy to maintain its thickness while being gradually compressed and deformed, and has excellent cushioning properties. That is, the nonwoven fabric 10 has excellent softness when touching the skin. In addition, when the nonwoven fabric 10 is used as a member on the skin side of the absorbent body in an absorbent article, such as a top sheet, the liquid permeation effect of excreted liquid is more likely to be sustained even under load, and liquid return (wetback) from the absorbent body to the skin side is suppressed. The three-dimensional shape of the wall portion 1B that acts in this way can be well maintained by being integrated with the second fiber layer M2 with high strength by the above-mentioned fiber fusion part. In addition, since this integration utilizes the bonded state at the intersections of the fibers fused together, there is no need to collapse the lower part of the wall 1B to secure a bonding surface as in the case of bonding with a conventional hot melt adhesive. This allows the wall 1B to maintain a sufficient height. In addition, the liquid can be promoted to fall toward the second fiber layer M2 along the longitudinal orientation of the wall 1B.

[0016] The longitudinal orientation of the fibers in the wall portion 1B means that many fibers are aligned along the thickness direction Z of the first fiber layer M1, and that the longitudinal orientation rate obtained by the measurement method described below is 60% or more. From the viewpoint of further enhancing the above-mentioned effect, 61% or more is preferable, and 62% or more is more preferable. There is no particular upper limit to the longitudinal orientation rate, but from the viewpoint of forming intersections between oriented fibers to form fused parts and forming columns between the fibers to form a structure that can withstand force, it is preferable that the longitudinal orientation rate is 90% or less, more preferably 85% or less, and even more preferably 80% or less.

[0017] (Method of measuring longitudinal orientation rate of fibers in wall portion 1B) As shown in FIG. 1, the wall portion 1B is measured in the following procedure. That is, the fiber layer cross section of the wall portion 1B defined in the cross section in the thickness direction of the nonwoven fabric 10, including the convex portion 1, the bottom portion 2, and the second fiber layer M2 of the first fiber layer M1, is observed at 35 times magnification with a scanning electron microscope (SEM). A square line with a side of 500 μm is added to the observed image as a reference line. Each side (reference line) of the square is defined as a side perpendicular to the thickness direction and the planar direction in the cross section of the nonwoven fabric 10. The total number of fibers passing through the reference line consisting of each side of the square is counted. The fibers passing through the square reference line perpendicular to the planar direction of the nonwoven fabric 10 are defined as the "number of horizontal fibers", and the fibers passing through the square reference line perpendicular to the thickness direction of the nonwoven fabric 10 are defined as the "number of vertical fibers". The longitudinal orientation rate is calculated as (number of vertical fibers) / (number of horizontal fibers+number of vertical fibers)×100=longitudinal orientation rate (%). Ten points are measured for each, and the average is taken as the value of the longitudinal orientation rate. The planar direction in the cross section of the nonwoven fabric 10 corresponds to a straight line L tangent to the surface of the other side 10B of the second fiber layer M2 shown in Figure 1. The thickness direction corresponds to a direction Z perpendicular to the straight line L.

[0018] In the above-mentioned cross section in the thickness direction Z of the nonwoven fabric 10, including the protrusions 1 and the bottoms 2 of the first fiber layer M1, the fiber layer of the wall portion 1B can be divided by the following method. That is, a nonwoven fabric 10 having a cross section in the thickness direction Z including the top 1A and wall 1B of the first fiber layer M1 and the second fiber layer M2 is placed on the base of a microscope VHX6000 (product name, manufactured by Keyence Corporation) with the second fiber layer M2 (other surface side 10B) facing down. Next, a flat plate (e.g., a flat acrylic plate) is placed on the top 1A side (one surface side 10T) of the nonwoven fabric 10, and a pressure of 4.9 mN / cm is applied. 2 A load of 1000 MPa is applied to the cross section in the thickness direction Z. In this state, the cross section in the thickness direction Z is observed at 20 times by the microscope, and the fiber layer in the first fiber layer M1 that is in contact with the flat plate is designated as a top portion 1A. The portion connecting the end of the top portion 1A and the surface of one surface side 10T of the second fiber layer M2 is designated as a wall portion 1B. In specifying the boundary between top 1A and wall 1B, the thickness of top 1A in the portion without wall 1B is defined as the thickness of the end of top 1A, and the portion excluding this thickness is defined as wall 1B. Wall 1B has an end (also called base 1D) on the other surface side 10B, and bottom 2 refers to the region provided between adjacent protrusions 1, 1, including base 1D.

[0019] In addition, the wall 1B extends perpendicular to the planar direction of the nonwoven fabric 10. As described above, the wall 1B is joined to the second fiber layer M2 by the fused fiber portion, and is integrated with the second fiber layer M2 with high joining strength. This prevents the vertically extending structure of the wall 1B from collapsing during joining, and the wall 1B is easily held stably with the second fiber layer M2 as a base. When the nonwoven fabric 10 is incorporated as a member closer to the skin than the absorbent body in an absorbent article, such as a top sheet, the second fiber layer M2 can be joined to the lower layer member (such as the absorbent body) with sufficient joining strength while ensuring a joining area. This makes it easy to maintain the uneven structure including the wall 1B of the first fiber layer M1 even when the nonwoven fabric 10 is incorporated in an absorbent article.

[0020] The vertical wall 1B connects the top 1A and the second fiber layer M2 vertically. This makes it easy for the soft fiber layer of the top 1A to remain supported by the elastic fiber layer of the wall 1B. The thickness of the fiber layer of the protrusion 1 is felt through this top 1A, and the cushioning properties are enhanced. In addition, the second fiber layer M2 functions as a soft cushion base, and the cushioning properties of the vertical wall 1B connected to it become more flexible and excellent, and can be expressed more stably. This makes it easy to obtain a softer touch. More specifically, this soft touch is felt as a gentle and reassuring thickness under light pressure to the touch, and is felt as a resilient and soft thickness that is difficult to wear out even when the protrusion 1 deforms under further pressure. Such excellent cushioning properties further improve the feel of the skin due to the uneven structure described above. In addition, the vertical extension of the wall 1B promotes the descent of liquid along the wall 1B. This descent promotion effect is effective in improving the liquid absorbency of the absorbent article, particularly when the nonwoven fabric 10 is used as a member on the skin side of the absorbent body in the absorbent article, such as a top sheet. Generally, the absorbent article is arranged at an incline along the crotch area of ​​the wearer when worn, and depending on the amount and force of the excreted liquid (not only urine but also loose stools with fluidity), the excreted liquid may flow on the surface along the incline. However, in the nonwoven fabric 10 of this embodiment, the wall 1B of the first fiber layer M1 is inclined along the wearer's body as shown in FIG. 2(A) while extending perpendicularly to the planar direction of the nonwoven fabric 10, forming a wall like a levee, and exerts a high damming effect against the excreted liquid that tends to flow on the surface. Furthermore, the dammed excreted liquid is dropped into the recessed portion 2 between the protruding portions 1, 1 along the vertical shape of the wall 1B, suppressing the surface flow of the excreted liquid (arrow S1). In contrast, when the wall angle of the protrusions 9 is gentle as in the case of a conventional uneven nonwoven fabric 90 shown in Fig. 2(B), the wall 9B has a gentle slope relative to the above-mentioned inclination, so that the excreted liquid tends to flow along the surface of the wall 9B (arrow S2), and the blocking effect of the vertical wall 1B of the nonwoven fabric 10 is unlikely to occur. In this manner, in the nonwoven fabric 10 of this embodiment, the liquid blocking effect of the vertical wall 1B is exerted when the absorbent article is worn, and the above-mentioned effect of promoting the descent of the liquid is more effectively exerted, and as a result, the surface flow of the liquid can be suppressed and the liquid absorbency of the absorbent article can be improved. The above-mentioned cushioning effect and liquid descending promotion effect due to the vertical wall portion 1B are further enhanced when the fibers of the wall portion 1B are oriented vertically. Furthermore, as described above, the above-mentioned function of wall portion 1B can function effectively, particularly when nonwoven fabric 10 is incorporated into an absorbent article, because wall portion 1B is integrated with second fiber layer M2 with high bonding strength by the fiber fusion portion and the structure is maintained.

[0021] The "vertical" of the wall 1B means that the angle θ with respect to the plane of the other side 10B of the nonwoven fabric 10 (second fiber layer M2) shown in FIG. 1 is not limited to a case where the angle is strictly 90°, but is between 60° and 120°. When the angle is within this range, the wall 1B has a shape that extends at an angle that is substantially recognized as 90° in the thickness direction Z of the nonwoven fabric 10. The angle θ means the intersection angle between the plane tangent to the surface of the other side 10B of the nonwoven fabric 10 and the extension line of the wall 1B. Specifically, as shown in FIG. 1, in a cross section in the thickness direction Z including the convex portion 1, the angle θ means the interior angle of the angle formed by the center line M of the width of the fiber layer of the wall 1B and the straight line L tangent to the surface of the other side 10B of the nonwoven fabric 10 (second fiber layer M2). This angle θ can be obtained by observing a micrograph of the cross section obtained by the above-mentioned microscope.

[0022] 1, the wall 1B extends linearly between the top 1A and the second fiber layer M2, and the entire wall 1B is provided perpendicular to the second fiber layer M2. However, this is not limited thereto, and the wall 1B may include a portion extending in a curved or wavy manner between the top 1A and the second fiber layer M2. In this case, the angle θ is determined by taking the line connecting the boundary point between the top 1A and the wall 1B and the boundary point between the second fiber layer M2 and the wall 1B as the center line M. Although all of the walls 1B preferably extend perpendicular to the second fiber layer M2, some of the walls 1B may not extend perpendicular to the plane of the other surface 10B of the second fiber layer M2. In the latter case, the number of perpendicular walls 1B is preferably 60% or more of the walls 1B in all of the protrusions 1, from the viewpoint of further enhancing the cushioning properties and liquid descending promotion effect of the nonwoven fabric 10.

[0023] The bottom 2 of the first fiber layer M1 is provided between the adjacent protrusions 1, 1, and more specifically, refers to a region including the bottom of a recess (inter-protrusion recess 2U) recessed on the other surface side 10B between the protrusions 1, 1 and an end (root 1D) of the other surface side 10B of the wall portion 1B. The bottom 2 has an opening 3 penetrating in the thickness direction Z. In the example shown in FIG. 1, the entire bottom 2 except for the root 1D is the opening 3, and in this case, the root 1D of the wall portion 1B is the bottom 2. The penetration in the opening 3 here means that, when focusing on the first fiber layer M1, a portion of the first fiber layer M1 where no constituent fibers are arranged penetrates both sides of the first fiber layer M1 in the thickness direction Z. In the openings 3 arranged in the bottom portion 2, the discharged liquid guided to the bottom portion 2 by the liquid blocking effect and liquid descending promotion effect of the wall portion 1B described above can be rapidly permeated into the second fiber layer M2 with reduced pressure loss.

[0024] The openings 3 are holes formed by processing the first fiber layer M1, and have a hole area that is much larger than the fine holes formed between the fibers. In FIG. 1, the entire bottom 2 except for the base 1D is shown as the openings 3, but the size of the openings 3 can be appropriately selected depending on the width of the bottom 2, etc. For example, in the first fiber layer M1, the entire bottom 2 except for the base 1D may not be the openings 3, and a fiber layer extending from the base 1D may be present around the openings 3. At least 1.0 mm 2 It is preferable that the opening area is equal to or more than this. The size of the opening 3 can be measured using the above-mentioned microscope. Specifically, the area of ​​the opening 3 is measured at 10 points using the microscope, and the average value of these is regarded as the opening area of ​​each opening.

[0025] The hole area of ​​the opening 3 is set to 1.0 mm2 in order to enhance the liquid permeability. 2 More than 1.5mm is preferable. 2 More preferably, 2.0 mm or more 2 More preferably, the opening area of ​​the opening 3 is 50 mm 2 Less than 40mm is preferable 2Less than or equal to 35mm is preferred 2 The following is even more preferred:

[0026] The planar shape of the openings 3 may be various from the viewpoint of enhancing liquid permeability, and examples thereof include a circle, an ellipse, a rectangle, and a diamond.

[0027] The apertures 3 are located in the region sandwiched between the walls 1B of adjacent protrusions 1. This allows excreted liquid received from one surface side 10T to flow directly down the walls 1B to the apertures 3 and quickly permeate into the absorbent body underneath, when the nonwoven fabric 10 is used as a member on the skin side of an absorbent article, such as a topsheet, so that the liquid can be quickly transmitted through the absorbent body underneath, thereby improving the liquid transmission rate in the thickness direction Z of the nonwoven fabric 10. The outer peripheral edge of the opening 3 may be formed by the lower end of the wall 1B, and the constituent fibers of the first fiber layer M1 (constituent fibers of the bottom portion 2) may be arranged between the lower end of the wall 1B and the outer peripheral edge of the opening 3. When the constituent fibers of the first fiber layer M1 are present between the lower end (root portion 1D) of the wall portion 1B and the outer peripheral edge of the openings 3 (when the openings 3 are in part of the bottom portion 2 and the constituent fibers of the first fiber layer M1 are present in the bottom portion 2), the planar separation distance between the root portion 1D of the wall portion 1B and the outer peripheral edge of the openings 3 is preferably 0.5 mm or less from the viewpoint of the above-mentioned liquid permeability. Note that when the constituent fibers of the first fiber layer M1 are present in the bottom portion 2 in this manner, the constituent fibers of the first fiber layer M1 are not considered to be part of the wall portion 1B.

[0028] The second fiber layer M2 is disposed on the side where the bottom of the first fiber layer M1 is located, and the fibers constituting the second fiber layer M2 have a smaller fiber diameter than the fibers constituting the first fiber layer M1. Due to the smaller fiber diameter, the second fiber layer M2 has a higher number of fibers per unit area than the first fiber layer M1, and the capillary force between the fibers is increased, resulting in a larger difference in the capillary force between the second fiber layer M1 and the first fiber layer M1. Such a second fiber layer M2 is exposed on the side of the first fiber layer M1 at the aforementioned openings 3. That is, the second fiber layer M2, which has a stronger capillary force, is not covered by the first fiber layer M1 at the openings 3, and is exposed so as to be visible from one surface side 10T. As a result, the nonwoven fabric 10 has a structure in which the capillary force increased in the second fiber layer M2 spreads to the side of the first fiber layer M1 through the openings 3. This structure increases the force of the openings 3 to draw in the excreted liquid that has descended along the wall 1B to the second fiber layer M2. Moreover, the second fiber layer M2 can diffuse the drawn in excreted liquid on the other surface 10B of the nonwoven fabric 10 by its strong capillary force. This increases the liquid permeation rate from the first fiber layer M1 to the second fiber layer M2 and the ability to prevent liquid from remaining in the first fiber layer M1, improving the liquid permeability in the thickness direction of the nonwoven fabric 10. In addition, liquid return from the second fiber layer M2 to the first fiber layer M1 is suppressed. Such a liquid drawing effect achieved by combining the wall 1B, the openings 3, and the fiber diameter of the second fiber layer M2 is particularly effective in improving the liquid permeation rate of high-viscosity excreted liquid such as menstrual blood, which tends to remain in one place. The high viscosity mentioned above means a viscosity of more than 5 cP.

[0029] Furthermore, the second fiber layer M2 and the first fiber layer M1 (wall portion 1B) are joined and integrated by fiber fusion parts formed by heat fusion of the constituent fibers themselves, rather than by a conventional hot melt type adhesive, and therefore the adhesive is not exposed at the openings 3. This makes it possible to avoid the above-mentioned action at the openings 3 being hindered by the adhesive as in the conventional case.

[0030] Such nonwoven fabric 10 can have excellent cushioning properties and liquid permeability by utilizing the cooperation of the specific structure of wall portion 1B, the openings 3 in bottom portion 2 adjacent to base portion 1D of wall portion 1B, and the capillary force of second fiber layer M2. When nonwoven fabric 10 is used as a member on the skin side of the absorbent body in an absorbent article, such as a top sheet, the liquid absorbency of the absorbent article can be improved.

[0031] From the viewpoint of further increasing the ability of the second fiber layer M2 to draw in excreted liquid through the openings 3 of the first fiber layer M1, it is preferable that the hydrophilicity of the constituent fibers of the second fiber layer M2 is higher than that of the constituent fibers of the first fiber layer M1. Since the constituent fibers of the second fiber layer M2, which have a higher hydrophilicity than the constituent fibers of the first fiber layer M1, are exposed on the first fiber layer side at the openings 3, the excreted liquid that has descended down the wall 1B can be quickly drawn into the exposed parts with high hydrophilicity without being retained at the bottom 3.

[0032] The above-mentioned "hydrophilicity" is represented by the magnitude of the contact angle of the fiber obtained by the following measurement method. Specifically, low hydrophilicity is synonymous with large contact angle, and high hydrophilicity is synonymous with small contact angle. When synthetic fibers such as thermoplastic fibers are used, the hydrophilicity, i.e., the contact angle, of the fibers constituting the first fiber layer M1 and the second fiber layer M2 can be set by surface treatment with a water repellent agent and a hydrophilic agent. As the hydrophilic agent and the water repellent agent, various agents commonly used in this type of article can be used. The above hydrophilicity refers to the average hydrophilicity of the constituent fibers in each of the first fiber layer M1 and the second fiber layer M2.

[0033] The difference (G1-G2) between the contact angle (G1) of the constituent fibers of the first fiber layer M1 and the contact angle (G2) of the constituent fibers of the second fiber layer M2 is preferably 0.5 or more, more preferably 1.0 or more, and even more preferably 2.0 or more, from the viewpoint of further increasing the liquid-attracting power. Moreover, the difference (G1-G2) is preferably 50.0 or less, more preferably 45.0 or less, and even more preferably 40.0 or less, from the viewpoint of increasing the liquid-attracting power and promoting the transfer of liquid to the absorbent body. Furthermore, within the range satisfying the above-mentioned difference (G1-G2), from the viewpoint of increasing the ability to draw in excreted liquid, the contact angle (G2) of the constituent fibers of the second fiber layer M2 is preferably 85 or less, more preferably 82 or less, and even more preferably 80 or less. From the viewpoint of increasing the ability to draw in liquid while promoting the transfer of liquid to the absorbent body, the contact angle (G2) of the constituent fibers of the second fiber layer M2 is preferably 50 or more, more preferably 55 or more, and even more preferably 60 or more. In addition, within the range satisfying the above-mentioned difference (G1-G2), the contact angle (G1) of the constituent fibers of the first fiber layer M1 is preferably 60 or more, more preferably 65 or more, and even more preferably 70 or more, from the viewpoint of suppressing liquid residue. The contact angle (G1) of the constituent fibers of the first fiber layer M1 is preferably 89 or less, more preferably 88 or less, and even more preferably 85 or less, from the viewpoint of suppressing liquid flow.

[0034] (Method of measuring contact angle) Fibers are taken from three locations each on the top 1A and wall 1B of the first fiber layer M1, and from three locations each on the center of the thickness direction of the portion overlapping the aperture 3 of the second fiber layer M2 and the center of the thickness direction of the portion not overlapping, and the contact angle of water with the fibers is measured. An automatic contact angle meter MCA-J (product name) manufactured by Kyowa Interface Science Co., Ltd. is used as the measuring device. Distilled water is used for measuring the contact angle. The amount of liquid discharged from the inkjet water droplet discharge unit (CTC-25, a pulse injector with a 25 μm orifice diameter, manufactured by Cluster Technology Co., Ltd.) is set to 20 picoliters, and the water droplets are dropped directly onto the fiber. The dropping behavior is recorded on a high-speed recording device connected to a horizontally placed camera. From the viewpoint of later image analysis, a personal computer with a built-in high-speed capture device is preferable as the recording device. In this measurement, images are recorded every 17 msec. In the recorded video, the first image in which the water droplets land on the fiber taken out of the nonwoven fabric is analyzed using the attached software FAMAS (software version 2.6.2, analysis method is the droplet method, analysis method is the θ / 2 method, image processing algorithm is non-reflective, image processing image mode is frame, threshold level is 200, curvature correction is not performed), and the angle between the surface of the water droplet that is in contact with the air and the fiber is calculated, which is the contact angle. The fibers taken out of the nonwoven fabric are cut to a fiber length of 1 mm, and the fibers are placed on the sample stage of the contact angle meter and kept horizontal. The contact angle is measured at two different points for each fiber. The contact angles of three different points are measured to one decimal place, and the average value of the measured values ​​at a total of 12 points (rounded off to the second decimal place) is defined as the contact angle.

[0035] From the viewpoint of making the above-mentioned action due to the difference in capillary force more effective, the difference (E1-E2) between the fiber diameter (E1) of the constituent fiber of the first fiber layer M1 and the fiber diameter (E2) of the constituent fiber of the second fiber layer M2 is preferably 2 μm or more, more preferably 3 μm or more, and even more preferably 4 μm or more. From the viewpoint of improving the clarity of the openings, the difference (E1-E2) is preferably 50 μm or less, more preferably 40 μm or less, and even more preferably 30 μm or less. The constituent fibers of the second fiber layer M2, which have a smaller fiber diameter than the constituent fibers of the first fiber layer M1, are exposed to the first fiber layer side at the openings 3. In the vicinity of the openings 3, a structure is formed in which the wall portion 1B and / or the bottom portion 2 composed of the constituent fibers of the first fiber layer M1 and the constituent fibers of the second fiber layer M2 are partially entangled due to the difference in fiber diameter. This structure not only increases the clarity of the openings, but also increases the ability to draw in excreted liquids compared to a laminated nonwoven fabric in which two types of fiber layers are simply laminated together and there are no exposed areas. Furthermore, within the range of the difference (E1-E2), the fiber diameter (E2) of the fibers constituting the second fiber layer M2 is preferably 25 μm or less, more preferably 20 μm or less, and even more preferably 18 μm or less, from the viewpoint of enhancing the capillary force. The fiber diameter (E2) of the fibers constituting the second fiber layer M2 is preferably 3 μm or more, more preferably 5 μm or more, and even more preferably 8 μm or more, from the viewpoint of enhancing the liquid permeability. In addition, within the range of the difference (E1-E2), the fiber diameter (E1) of the fibers constituting the first fiber layer M1 is preferably 5 μm or more, more preferably 6 μm or more, and even more preferably 8 μm or more from the viewpoint of improving the texture. The fiber diameter (E1) of the fibers constituting the first fiber layer M1 is preferably 25 μm or less, more preferably 23 μm or less, and even more preferably 20 μm or less from the viewpoint of improving the feel on the skin. The above fiber diameter means the average fiber diameter of the constituent fibers in each of the first fiber layer M1 and the second fiber layer M2.

[0036] (Method of measuring average fiber diameter of constituent fibers of first fiber layer M1 and second fiber layer M2) The fiber diameter can be measured by observing the cross section of the fiber layer using the following method. The part to be measured (for example, the first fiber layer M1) is frozen under no load using cold spray or liquid nitrogen to fix the structure, and then cut in the thickness direction using a cutter blade to expose the cross section of the measurement part. The cross section is observed under magnification using a scanning electron microscope (JCM-5100 manufactured by JEOL Ltd.), and the magnification is adjusted to a value (100 to 500 times) at which the fiber cross section can be measured. Five observation photographs are taken in this state to obtain a cross-sectional observation photograph. Next, the central portion in the thickness direction of each of the first fiber layer M1 and the second fiber layer M2 is set as the measurement position, and the fiber diameters of 30 fibers per photograph are measured, and the arithmetic average value is the average fiber diameter of the present invention. When the fibers are non-circular, the line segment that connects two points on the periphery in the cross section and has the maximum across length of the cross section is set as the long axis, and the line segment that is perpendicular to the long axis and has the maximum length is set as the short axis, and the lengths of the long axis and the short axis are measured by analyzing and calculating them using image analysis software or the like, and the arithmetic average value of the long axis length and the short axis length of one fiber is set as the fiber diameter of each fiber, and the arithmetic average value of the fiber diameters of 30 fibers is set as the average fiber diameter of the fibers of the present invention. When the nonwoven fabric to be measured is incorporated in a sanitary product such as an absorbent article, the sanitary product is sprayed with cold spray to solidify the hot melt adhesive, and then the nonwoven fabric to be measured is carefully peeled off. This method is common to other measurements in this specification.

[0037] Similarly, in order to make the above-mentioned effect due to the difference in capillary force more effective, it is preferable that the number of fibers per unit area of ​​the second fiber layer M2 is greater than the number of fibers per unit area of ​​the top portion 1A in the first fiber layer M1. More specifically, the difference (F2-F1) between the number of fibers per unit area in the second fiber layer M2 (F2) and the number of fibers per unit area in the top portion 1A in the first fiber layer M1 (F1) is preferably at least 5, more preferably at least 8, and even more preferably at least 10. From the viewpoints of increasing the liquid-drawing force and promoting the transfer of liquid to the absorbent body, the difference (F2-F1) is preferably at most 190, more preferably at most 185, and even more preferably at most 180. Furthermore, within the range of the difference (F2-F1), from the viewpoint of enhancing capillary force, the number of fibers (F2) per unit area of ​​the second fiber layer M2 is preferably 80 or more, more preferably 85 or more, and even more preferably 90 or more. From the viewpoint of enhancing liquid permeability, the number of fibers (F2) per unit area of ​​the second fiber layer M2 is preferably 200 or less, more preferably 190 or less, and even more preferably 180 or less. In addition, within the range satisfying the above difference (F2-F1), from the viewpoint of suppressing liquid residue, the number of fibers (F1) per unit area of ​​the top portion 1A in the first fiber layer M1 is preferably 90 or less, more preferably 85 or less, and even more preferably 80 or less. From the viewpoint of improving the feel on the skin, the number of fibers (F1) per unit area of ​​the top portion 1A in the first fiber layer M1 is preferably 20 or more, more preferably 25 or more, and even more preferably 30 or more. The number of fibers per unit area means the average number of constituent fibers in each of the first fiber layer M1 and the second fiber layer M2.

[0038] (Method of measuring the number of fibers per unit area of ​​the first fiber layer M1 and the second fiber layer M2) The number of fibers per unit area of ​​the first fiber layer M1 is measured at the center in the thickness direction of the top portion 1A, and the number of fibers per unit area of ​​the second fiber layer M2 is measured at the center in the thickness direction at the part overlapping with the opening portion 3. Specifically, the cross section of the nonwoven fabric 10 is observed and the number of fiber cross sections is counted according to the following procedure. First, cross sections are prepared for the site to be measured along two directions, the longitudinal direction of the nonwoven fabric 10 and the width direction perpendicular to the longitudinal direction (for example, the cross sections shown in Fig. 5 and Fig. 6 for a nonwoven fabric 20 described below). If it is not possible to prepare a cross section that includes both the top portion 1A of the first fiber layer M1 and the portion overlapping with the open hole 3 of the second fiber layer M2, cross sections in the above two directions may be prepared for each site. Next, a scanning electron microscope (JCM-6000Plus (product name) manufactured by JEOL Ltd.) is used to enlarge and observe the cross section at a magnification (100 to 500 times) that allows measurement of about 2 to 40 fiber cross sections. At this time, metal vapor deposition is performed on the cross section. The top portion 1A of the first fiber layer M1 is subjected to a certain area (0.12 mm 2 The number of cut fiber cross sections in the cut surface of the fiber was counted and divided by the fixed area to obtain the unit area (1 mm 2 The average of the 10 points (5 locations + 5 locations) is calculated as the number of fibers per unit area (fibers / mm2) of the first fiber layer M1. 2) Similarly, the portion of the second fiber layer M2 overlapping with the openings 3 is measured and converted in the same manner as above at five points in each of the cross sections in the two directions. The average of the total of 10 points is calculated as the number of fibers per unit area (fibers / mm 2 ) The above-mentioned large number of fibers per unit area means that the fiber density is high, and that the capillary force acts more strongly.

[0039] In the nonwoven fabric 10, as shown in Fig. 1 and Fig. 3, the second fiber layer M2 preferably has a protruding portion 5 on the surface facing the first fiber layer M1, which protrudes from the opening 3 of the first fiber layer M1 into the region defined by the wall portion 1B. In this case, the protruding portion 5 is on one surface side 10T of the base portion 1D of the wall portion 1B in the above-mentioned contact region 4, and is in the space sandwiched by the wall portion 1B between the protruding portions 1, 1 of the first fiber layer M1. Meanwhile, the second fiber layer M2 in the contact region 4 adjacent to the protruding portion 5 forms a recessed portion 6 due to being bitten into by the wall portion 1B. In the recessed portion 6 in the contact region 4, the first fiber layer M1 (i.e., the base portion 1D of the wall portion 1B) and the second fiber layer M2 are integrated by a fiber fusion portion in which the fibers of each layer are fused to each other.

[0040] Since the protrusions 5 made of the constituent fibers of the second fiber layer M2 extend from the openings 3 into the first fiber layer M1, the excreted liquid that has flowed down along the wall 1B is more quickly drawn in by the capillary force of the second fiber layer M2 (for example, arrow S3 in FIG. 3), and the amount of liquid remaining in the first fiber layer M1 is further reduced. This further improves the liquid permeation rate in the thickness direction Z of the nonwoven fabric 10. In this way, the liquid permeability is further improved. In order to make the above-mentioned action more effective, it is preferable that the surface of the protuberance 5 has fuzz that extends further to the one surface side 10T. Furthermore, the presence of the raised portions 5 prevents the wall portions 1B from collapsing sideways due to external pressure, and the various functions of the wall portions 1B described above can be maintained. This makes it possible to provide the nonwoven fabric 10 with both excellent cushioning properties and liquid permeability.

[0041] The raised portion 5 is visible from the first fiber layer M1 side because it enters the first fiber layer M1 at the position of the opening 3 penetrating the first fiber layer M1 in the thickness direction Z. Therefore, when the nonwoven fabric 10 is viewed from the first fiber layer M1 side (one surface side 10T), the convex portion 1 of the first fiber layer M1 and the raised portion 5 of the second fiber layer M2 are visually recognized as being adjacent to each other. At this time, the shadow around the opening 3 at the bottom 2 of the first fiber layer M1 is emphasized by the presence of a valley formed by the base portion 1D of the wall portion 1B constituting the convex portion 1 and the bottom portion 7 of the raised portion 5 extending to the base portion 1D. When the fibers of the wall portion 1B are longitudinally oriented, the raised portion 5 is made of a fiber layer having a fiber orientation different from that of the wall portion 1B, and a dividing line is formed where the fiber orientation degree changes discontinuously between the two portions, which further emphasizes the shadow. In addition, since the wall 1B has a vertical wall surface, the valley between the raised portion 5 at the base portion 1D of the wall 1B becomes narrower and the shadow becomes stronger. The shadow can be recognized as floating from the vertical wall 1B. Since the raised portion 5 is thus visible from the side of the first fiber layer M1, consumers of an absorbent article having the nonwoven fabric 10 as a top sheet can visually see that the nonwoven fabric has clear openings. As a result, consumers can imagine that the absorbent article has excellent liquid absorption properties and can use the article with confidence. In the example shown in FIG. 1, the entire bottom 2 except for the base 1D is the opening 3, and the bottom 7 of the protuberance 5 is directly connected to the base 1D of the wall 1B. However, the present invention is not limited to this embodiment, and a fiber layer may be present around the opening 3 in the inter-protrusion recess 2U of the first fiber layer M1. In this case, the bottom 7 of the protuberance 5 of the second fiber layer M2 extends to the base 1D of the wall 1B through the fiber layer around the opening 3 in the inter-protrusion recess 2U, forming the valley and the dividing line. Similarly, when a fiber layer is present in the inter-protrusion recess 2U, the wall 1B is embedded in the second fiber layer M2 through the inter-protrusion recess 2U and the base 1D in the bottom 2.

[0042] In the nonwoven fabric 10, the above-mentioned emphasis of the shading improves the visibility of the openings 3 when viewed from the first fiber layer M1 side (one surface side 10T). In particular, when the nonwoven fabric 10 is placed on the skin-facing side of an absorbent body as a top sheet of an absorbent article, the shadows around the openings 3 of the nonwoven fabric 10 are more emphasized against the white background of the absorbent body, and the visibility of the openings 3 is significantly improved, making the high absorbency of the absorbent article obvious.

[0043] This visibility makes it easier for a user to understand the liquid permeability through the apertures 3 of the topsheet of an absorbent article incorporating the nonwoven fabric 10 as a topsheet, ie, the good absorbency of the absorbent article.

[0044] From the viewpoint of enhancing the effect of highlighting the shadow between the root portion 1D of the wall portion 1B and the protuberance 5, it is preferable that the surface side of the second fiber layer M2 facing the first fiber layer M1 is a continuous fiber layer extending in the planar direction. In this way, the surface side of the second fiber layer M2 facing the first fiber layer M1 is a continuous fiber layer extending in the planar direction, so that the above-mentioned shadow portion becomes more noticeable as a different portion in the continuous fiber layer. In addition, when the fibers of the wall portion 1B of the first fiber layer M1 are oriented vertically, a dividing line where the fiber orientation changes discontinuously between the first fiber layer M1 and the second fiber layer M2 is formed, and the shadow is enhanced.

[0045] From the same viewpoint, it is preferable that the bottom 7 extending downward from the raised portion of the protuberance 5 is connected to the contact region 4 between the wall portion 1B of the first fiber layer M1 and the second fiber layer M2. By connecting the bottom 7 to the contact region 4 in this manner, a valley is formed by the base portion 1D of the wall portion 1B and the bottom 7, and the shadow around the opening 3 in the bottom portion 2 of the first fiber layer M1 is emphasized.

[0046] From the viewpoint of making the above-mentioned emphasis on shadows more clear, it is preferred that in the contact region 4 of the first fiber layer M1 between the wall portion 1B and the second fiber layer M2, the fibers of the second fiber layer M2 are oriented in the planar direction, and the fibers on the surface of the skirt portion 7 of the protuberance 5 have a fiber orientation different from that of the fibers of the wall portion 1B. By having the fibers on the surface of the skirt portion 7 have a fiber orientation different from that of the fibers of the wall portion 1B in this way, a dividing line is formed where the fiber orientation on the surface of the skirt portion 7 and the fiber orientation of the wall portion 1B change discontinuously, thereby emphasizing the shadows. The fibers on the surface of the base 7 of the raised portion 5 refer to the fibers in the portion that starts to rise from the base 1D of the wall portion 1B in the contact region 4. For example, the surface fibers of the raised portion 5 within a range of 2 mm from the base 1D. Specifically, the fiber orientation on the surface of the skirt portion 7 is a longitudinal orientation rate of less than 45%. A longitudinal orientation rate of less than 45% means that the fibers are oriented in a planar direction, and the longitudinal orientation rate is different from that of the fibers in the wall portion 1B, making the above-mentioned shadow clearer. Here, the fibers on the surface of the skirt portion 7 having a fiber orientation different from that of the fibers in the wall portion 1B means that the difference in longitudinal orientation rate between the two is 15% or more. From the viewpoint of further enhancing the above-mentioned effect, a ratio of 20% or more is preferable, and 30% or more is more preferable.

[0047] (Method of measuring the longitudinal orientation rate of fibers on the surface of the bottom part 7) As shown in FIG. 1, measurements are performed on the bottom hem 7 in the following procedure. That is, a cross section of the fiber layer including the protrusions 1 of the first fiber layer M1 and the skirt 7 defined in the cross section of the nonwoven fabric 10 in the thickness direction, including the second fiber layer M2, is observed at 35 times magnification with a scanning electron microscope (SEM). A square line with a side of 500 μm is drawn on the observed image as a reference line. At this time, the line is drawn so that the fibers of the skirt 7 are included in the entire area of ​​the square. Each side (reference line) of the square is defined as a side perpendicular to the thickness direction and the planar direction in the cross section of the nonwoven fabric 10. The total number of fibers passing through the reference line consisting of each side of the square is counted. The fibers passing through the square reference line perpendicular to the planar direction of the nonwoven fabric 10 are defined as the "number of horizontal fibers", and the fibers passing through the square reference line perpendicular to the thickness direction of the nonwoven fabric 10 are defined as the "number of vertical fibers". The longitudinal orientation rate is calculated as (number of vertical fibers) / (number of horizontal fibers+number of vertical fibers)×100=longitudinal orientation rate (%). Ten points are measured for each film, and the average is taken as the longitudinal orientation ratio.

[0048] The ratio (H2 / H1) of the thickness H2 of the protrusion 5 to the thickness H1 of the first fiber layer M1 is preferably 0.05 or more, more preferably 0.10 or more, and even more preferably 0.15 or more, from the viewpoint of further enhancing the above-mentioned shadow. From the viewpoint of maintaining liquid permeability through the openings 3, the ratio (H2 / H1) of the thickness H2 of the protrusions 5 to the thickness H1 of the first fiber layer M1 is preferably 0.9 or less, more preferably 0.8 or less, and even more preferably 0.7 or less. The thickness H1 of the first fiber layer M1 refers to the height from the surface of one side 10T of the top portion 1A to the boundary with the second fiber layer M2 at the base portion 1D of the wall portion 1B in the contact region 4. 2 This can be done in the same manner as the method for dividing the fiber layer of the wall portion 1B described above, with the load of 100 being applied. In addition, if there is fuzz on the surface of the raised portion 5, this portion is included in the thickness H2 of the raised portion 5.

[0049] The basis weight of the nonwoven fabric 10 is set to 20 g / m2 in order to improve the texture of the nonwoven fabric and enhance the shading of the openings. 2 More than 30 g / m is preferable. 2 More preferably, 40 g / m 2 The weight of the nonwoven fabric 10 is preferably 100 g / m2 or more so as not to impede the comfortable feel of the wearer. 2 Less than 90 g / m 2 Less than 85 g / m is more preferable. 2 The following is even more preferred:

[0050] Nonwoven fabric 10: 4.9mN / cm 2 (0.05gf / cm 2 ) The thickness under load is preferably 0.8 mm or more, more preferably 1.0 mm or more, and even more preferably 1.2 mm or more, from the viewpoint of further emphasizing the shadow of the opening 3. This thickness is 4.9 mN / cm 2 The above 4.9mN / cm can be measured using a laser displacement meter or similar device under a load. 2 The load is a load that assumes fluffing on the surface of the nonwoven fabric. 2 By having the thickness under load within the above range, the liquid backflow prevention performance is improved, making it difficult for the wearer's skin to become wet. In addition, the nonwoven fabric 10 has a strength of 4.9 mN / cm 2The thickness under load is preferably 10 mm or less, more preferably 7 mm or less, and even more preferably 5 mm or less, from the viewpoint of not impeding the wearer's comfortable use.

[0051] Next, a more preferred embodiment of the uneven structure described above in the nonwoven fabric 10 of this embodiment will be described.

[0052] In the first fiber layer M1, it is preferable that a hollow region 1C exists between the second fiber layer M2 and the inside of the protrusion 1. The hollow region 1C is a space that is not substantially filled with the fibers of the nonwoven fabric 10. Specifically, the number of fibers per unit area, which is determined by the method described below, is 10 fibers / mm 2 The smaller the number of fibers per unit area in the hollow region 1C, the better. Furthermore, from the viewpoint of improving the cushioning properties and liquid permeability of the nonwoven fabric 10, it is preferable that the raised portions 5A of the second fiber layer M2 partially penetrate into the hollow regions 1C of the first fiber layer M1. The number of fibers per unit area in the hollow region 1C can be measured by applying the above-mentioned (method of measuring the number of fibers per unit area in the first fiber layer M1 and the second fiber layer M2) mutatis mutandis.

[0053] The hollow region 1C on the other surface side 10B of the projections 1 further improves the soft feel of the projections 1, further enhances the cushioning properties described above, and further improves the feel of the nonwoven fabric 10. When the nonwoven fabric 10 is used as a member on the skin side of the absorbent body, such as a top sheet of an absorbent article, the presence of the hollow region 1C cuts off the liquid return path from the absorbent body, improving the prevention of liquid return. In addition, the hollow region 1C also serves as a primary storage space in the event of excessive excretion, further improving the liquid permeability of the nonwoven fabric 10 and further reducing the amount of liquid remaining on the one surface side 10T.

[0054] Next, a specific example (nonwoven fabric 20) of the nonwoven fabric 10 shown in Fig. 1 will be described with reference to Fig. 4 to Fig. 7. The nonwoven fabric 20 has the configuration described above for the nonwoven fabric 10. 4 to 7, in plan view from one surface side 20T, the nonwoven fabric 20 has a plurality of ribs 11 extending in one direction Y as the protrusions 1 of the first fiber layer M1 and spaced apart from each other in a direction X intersecting the one direction Y. A hollow region 11C is provided between the rib 11 and the second fiber layer M2 on the other surface side 20B. The one direction Y and the direction X intersecting the one direction Y can be appropriately set according to the purpose on one surface side 20T of the nonwoven fabric 20. For example, the one direction Y and the direction X intersecting the one direction Y are preferably perpendicular to each other. When the nonwoven fabric 20 is used as a member on the skin side of an absorbent body, such as a topsheet in an absorbent article, it is preferable that the one direction Y is the longitudinal direction of the absorbent article, and the direction X intersecting the one direction Y is the width direction of the absorbent article.

[0055] The ridges 11 have the same height in the extension direction. The "same height" means that the height measured using a microscope VHX900 (product name, manufactured by Keyence Corporation) is within a range of 0.8 to 1.2 times the average measurement value.

[0056] Each of the ridges 11 includes a crest 11A and a wall 11B supporting the crest 11A. The crest 11A is a fiber layer that contacts the wearer's skin in an absorbent article, and the wall 11B is a fiber layer that connects the crest 11A and the second fiber layer M2 in the thickness direction. That is, when the nonwoven fabric 20 is applied to an absorbent article, the one surface side 20T becomes the skin contact surface side, and the other surface side 20B becomes the non-skin contact surface side. As described above, it is preferable that the fibers of the wall 11B are vertically oriented. In addition, the shape of the wall extends perpendicular to the second fiber layer M2, and vertically connects the crest 11A and the bottom 12 where the openings 3 are arranged. The longitudinal orientation ratio, which indicates the longitudinal orientation of the fibers in this wall portion 11B, can be measured based on the above-mentioned method (method for measuring the longitudinal orientation ratio of fibers in wall portion 1B) in a cross section perpendicular to the extension direction of the rib portion 11 (a thickness direction cross section at the position of line R1-R1 along direction X intersecting with direction Y in FIG. 4), as shown in FIG. 5. The angle θ, which indicates the "perpendicularity" of the wall portion 11B, refers to the interior angle between the center line M of the width of the fiber layer of the wall portion 11B and a straight line L tangent to the surface of the other side 20B of the nonwoven fabric 20 (the second fiber layer M2) in a cross section perpendicular to the extending direction of the rib portion 11 (a thickness direction cross section at the position of the line R1-R1 along the direction X intersecting with the one direction Y in FIG. 4), as shown in FIG. 5. This angle θ can be obtained by observing a micrograph of the cross section along the line R1-R1 obtained by the microscope described above.

[0057] The nonwoven fabric 20 has, as the above-mentioned convex portion 1 in the first fiber layer M1, the above-mentioned ridge portion 11 and the saddle portion 15 connecting the adjacent ridge portions 11, 11. The saddle portion 15, like the ridge portion 11, protrudes from the second fiber layer M2 to one surface side 20T of the nonwoven fabric 20, and is a three-dimensional fiber layer erected in the thickness direction of the nonwoven fabric 20. More specifically, the saddle portion 15 has a crest 15A on one surface side 20T and a wall portion 15B supporting the crest 15A. The fibers of the wall portion 15B are preferably vertically oriented as described above. In addition, the wall portion 15B extends perpendicular to the second fiber layer M2. The above-mentioned "perpendicular" has the same meaning as the "perpendicular" defined in the above-mentioned ridge portion 11. The longitudinal orientation rate indicating the longitudinal orientation of wall portion 15B in saddle portion 15 and the "vertical" of wall portion 15B can be measured in a cross section perpendicular to the extension direction of saddle portion 15 (thickness cross section at the position of line R2-R2 along one direction Y in FIG. 4) as shown in FIG. 6 in the same manner as the measurement method described above for wall portion 11B.

[0058] The above structure makes it difficult for the ridges 11 connected by the saddle portion 15 to approach each other, and prevents the ridges 11 from falling in one direction due to an external force such as pressure. That is, the saddle portion 15 supports the ridges 11 from the side, improving the shape retention of the ridges 11. This makes it easier for the ridges 11 to maintain their thickness under load. For example, when the nonwoven fabric 20 is incorporated into an absorbent article as a top sheet, even if there is body pressure from the wearer when wearing the absorbent article, the distance between the top portion 11A and the absorbent body side of the other surface side (non-skin contact surface side) 20B is easily maintained, making it even harder for liquid to return to the one surface side (skin contact surface side) 20T. Furthermore, the presence of the saddle portion 15 acts to block excreted liquid between the ridges 11, 11, enhancing the ability to prevent liquid from flowing on one surface side (skin contact surface) 20T of the nonwoven fabric 20.

[0059] In a plan view from one surface side 20T of the nonwoven fabric 20, the saddle portion 15 extends in a direction X intersecting with the direction Y in which the rib portion 11 extends. The direction X in which the saddle portion 15 extends can be various directions as long as it connects adjacent ribs 11, and is preferably a direction perpendicular to the direction Y in which the rib portion 11 extends. For example, it is preferable that the direction Y in which the rib portion 11 extends is the longitudinal direction of the absorbent article, and the direction X in which the saddle portion 15 extends and intersects with the direction Y is the width direction of the absorbent article. Hereinafter, the direction Y and the direction X perpendicular to the direction Y are also referred to as the extension direction Y of the rib portion 11 and the extension direction X of the saddle portion 15. In addition, the planar shape of each saddle portion 15 as viewed from one surface side 20T is not limited to a rectangle as shown in Fig. 4, and may be various shapes. For example, the planar shape of the saddle portion 15 as viewed from one surface side 20T may be such that the width increases toward the ridge portion 11.

[0060] The saddle portions 15 are arranged in a plurality of band regions 16 extending parallel to the ribs 11 between the ribs 11, 11 in a plan view of one surface side 20T of the nonwoven fabric 20. In each band region 16, a plurality of saddle portions 15 are arranged at intervals along the extension direction Y of the ribs 11 running in parallel. The above-mentioned openings 3 of the bottom portion 12 are located at the intervals between the saddle portions 15. That is, in each band region 16, the saddle portions 15 and the openings 3 are alternately arranged. As a result, the openings 3 are surrounded by the wall portions 11B of the ribs 11 and the wall portions 15B of the saddle portions 15. More specifically, the region surrounded by the plurality of ribs 11 and the plurality of saddle portions 15, which are three-dimensional fiber layers erected in the thickness direction, is a box-shaped or cylindrical recess, and the openings 3 are arranged in the bottom portion 12.

[0061] In the example shown in FIG. 4 to FIG. 7, in a plan view from one surface side 20T of the nonwoven fabric 20, the ridges 11 and the saddles 15 are arranged in a lattice pattern, and the openings 3 of the bottom 12 are arranged in a square pattern by being scattered in the lattice. The raised portions 5 of the second fiber layer M2 enter the lattice-shaped recessed spaces partitioned by the walls 11B and 15B from the openings 3 surrounded by the ridges 11 and the saddles 15. In this way, the raised portions 5 of the second fiber layer M2 are surrounded by the walls 11B and 15B in a lattice pattern, thereby further enhancing the cushioning properties, the liquid blocking action and the liquid descending promotion action of the walls 11B and 15B, further improving the liquid permeation speed to the second fiber layer M2 side, and further reducing the amount of liquid remaining. That is, both the cushioning properties and the liquid permeability can be further improved. In addition, the shadows around the openings 3 are further emphasized, which is preferable. That is, the four walls 11B and 15B surrounding the raised portion 5 have contact areas 4 with the second fiber layer M2, and valleys and shadows between the base portions 1D of the walls 11B and 15B and the bottom portions 7 of the raised portion 5 are formed on all four sides, so that the contours of the raised portion 5 and the openings 3 can be more clearly seen.

[0062] Although the saddle portion 15 has a three-dimensional fiber structure similar to that of the ridge portion 11, it is preferable that the saddle portion 15 has a portion that is lower in height from the bottom portion 12 than the ridge portion 11, as shown in Figures 6 and 7. This reduces the contact area with the skin on one surface side 20T of the nonwoven fabric 20, maintaining a pleasant feel against the skin, and increasing breathability to further prevent stuffiness between the surface and the skin. The difference (H3-H4) between the thickness direction height H3 of the rib portion 11 and the thickness direction height H4 of the saddle portion 15 is preferably 0.5 mm or more and 7.0 mm or less in order to improve the above-mentioned action. The thickness direction height H3 of the rib portion 11 is the thickness direction distance from a plane contacting the surface of the other side 20B of the nonwoven fabric 20 (second fiber layer M2) to one side 20T of the crest 11A of the rib portion 11. The thickness direction height H4 of the saddle portion 15 is the thickness direction distance from a plane contacting the surface of the other side 20B of the nonwoven fabric 20 (second fiber layer M2) to one side 20T of the lowest position of the crest 15A of the saddle portion 15.

[0063] (Method of measuring the difference between the height H3 of the ridge portion 11 in the thickness direction and the height H4 of the saddle portion 15 in the thickness direction) As shown in FIG. 6, a thickness direction cross section (thickness direction cross section at the position of line R2-R2 along one direction Y in FIG. 4) of the nonwoven fabric 20 is prepared at the lowest position of the saddle portion 15 along the extension direction of the band region 16 in which the saddle portions 15 are arranged, and the nonwoven fabric 20 is placed on a horizontal table so that the surface of the other side 20B of the second fiber layer M2 abuts against the horizontal table. The height H3 from the horizontal table to one side 20T of the crest 11A of the ridge portion 11 and the height H4 from the horizontal table to one side 20T of the crest 15A of the saddle portion 15 are measured. The height difference (H3-H4) is calculated from these measured values. The above-mentioned microscope can be used to measure the height from the horizontal table.

[0064] In addition, it is more preferable that the saddle portion 15 has a hollow region 15C as shown in FIG. 6 from the viewpoint of increasing the liquid permeability of the nonwoven fabric 20 and the dryness of the one side 20T due to the liquid permeability when the nonwoven fabric 20 is used as a top sheet of an absorbent article, and from the viewpoint of further promoting drainage to the other side 20B. The definition and measurement method of this hollow region 15C are the same as those of the hollow region 11C in the ridge portion 11. It is preferable that the hollow region 15C of the saddle portion 15 communicates with the hollow region 11C of the ridge portion 11. This increases the liquid permeability of the nonwoven fabric 20, promotes the diffusion of excreted liquid on the other side 20B, and further suppresses liquid retention on the one side 20T. As a result, the amount of liquid remaining in the nonwoven fabric 20 is more likely to be reduced, and the amount of liquid adhering to the skin can be further reduced.

[0065] Furthermore, as shown in the cross section in the extending direction of the saddle portion 15 in Fig. 7 (thickness direction cross section at the position of the line R3-R3 along the direction X intersecting with the direction Y in Fig. 4), it is preferable that the hollow portion 15C of the saddle portion 15 is connected to the hollow portion 11C of the rib portion 11 at the intersection of the saddle portion 15 and the rib portion 11. This allows liquid to flow vertically and horizontally between the hollow portion 15 and the hollow portion 11C on the other surface side 20B of the first fiber layer M2, thereby improving the liquid drawing ability of the second fiber layer M2. In addition, the breathability between the hollow portion 15 and the hollow portion 11C is improved, and stuffiness can be suppressed.

[0066] Next, a preferred embodiment of a method for producing the nonwoven fabric 20 will be described with reference to Figures 8 to 11. The production method described below can also be applied to the production method for the nonwoven fabric 10. As shown in FIG. 8, the manufacturing method of this embodiment includes the following four steps (hereinafter, each step may be referred to as step (I), step (II), step (III), and step (IV)). (I) A pressing process in which a first fiber web 100 is placed on a support 120 having an uneven shape with a plurality of protrusions 121 and recesses 125 between the protrusions 121, 121, and the first fiber web 100 is pressed along the recesses 125 by a pressing portion 131 of a pressing member 130 to form a shape, and holes are opened at the locations corresponding to the protrusions 121, thereby forming an uneven open-hole fiber web 101 having an open surface on the opposite side to the support 120. (II) A step of removing the pushing member from the support, and then blowing a first hot air W1 onto the porous fibrous web 101 to fuse the fibers together to obtain a porous nonwoven fabric 102. (III) A step of supplying a second fibrous web 103 having constituent fibers with a smaller fiber diameter than the first fibrous web 100 and laminating it on the open-pore surface side of the unevenly perforated nonwoven fabric 102. (IV) A heat-sealing step of blowing a second hot air W2 to fuse the fibers of the porous nonwoven fabric 102 and the second fibrous web 103 together and to fuse the fibers in the second fibrous web 103 together.

[0067] The first fibrous web 100 is a precursor of the first fibrous layer M1 in the nonwoven fabric 20 and contains thermoplastic fibers. The second fibrous web is a precursor of the second fibrous layer M2 in the nonwoven fabric 20 and contains thermoplastic fibers. The "fiber web" of the first fiber web 100 and the second fiber web 103 refers to a fiber assembly in which constituent fibers including thermoplastic fibers are not fused and fixed but are loosely entangled, and which does not have the shape retention of a sheet by itself. In other words, it is a fiber assembly before being made into a nonwoven fabric. Therefore, the mobility between fibers in the fiber web is high, and the deformation of the fiber web in the pushing process is high. Such first fiber web 100 and second fiber web 103 are each supplied from a carding machine (not shown) to a predetermined thickness.

[0068] In step (I), as shown in FIG. 8(A), the first fiber web 100 on the support 120 is directly pressed with mechanical pressure using a pressing member 130. This forms an uneven perforated fiber web 101 that will become the first fiber layer M1 in the nonwoven fabric 20. This type of shaping results in stronger fiber orientation and a perpendicular orientation to the nonwoven fabric plane compared to pressing with non-mechanical pressure such as wind. Furthermore, it is not necessary to apply a large pressing force to increase the unevenness height difference formed on the first fiber web 100, and the first fiber web 100 can be shaped softly. Furthermore, fiber disorder can be suppressed to improve shaping properties.

[0069] The support 120 is drum-shaped as shown in Fig. 8, for example, and has protrusions 121 as shown in Fig. 8(A) on the drum peripheral surface. On the drum peripheral surface of the support 120, a plurality of protrusions 121 are arranged at intervals in one direction (first direction D1) and a direction perpendicular thereto (second direction D2), as shown in Fig. 9, for example. A plurality of protrusion rows 121A, each of which is formed by arranging a plurality of protrusions 121 in the first direction D1, are arranged at a distance from each other in the second direction D2. The protrusions 121 have peaks 122 at their tips. The peaks 122 form the openings 3 in the bottom portion 12 of the first fiber layer M1. The planar shape of the projection 121 as viewed from the spire 122 side is not limited to a rectangle as shown in Fig. 9, but may be various shapes, such as a circle, an ellipse, or a diamond. The recess 125 has a first recess 125A extending in the first direction D1 between the protrusion rows 121A, 121A, and a second recess 125C located between the protrusions 121, 121 in the protrusion row 121A. The second recess 125C is connected to the adjacent first recess 125A and extends intermittently in the second direction D2 via the first recess 125A.

[0070] In the support 120, a plurality of protrusions 121 are arranged corresponding to positions where the openings 3 are to be formed in the bottom portion 12 of the first fiber layer M1 of the nonwoven fabric 20. The second recesses 125C between the protrusions 121, 121 in the protrusion row 121A are located at positions where the saddle portions 15 of the first fiber layer M1 of the nonwoven fabric 20 are formed. In other words, the protrusion row 121A is located at a position that will become the band regions 16 between the ribs 11, 11 in the first fiber layer M1 of the nonwoven fabric 20. The first recesses 125A are located at a position that will become the ribs 11 in the first fiber layer M1 of the nonwoven fabric 20. The bottom of each recess 125 has a structure that allows hot air to pass through, and for example, has a plurality of holes (not shown).

[0071] The pushing member 130 is in the form of a roll as shown in Fig. 8, for example, and has a pushing portion 131 as shown in Fig. 8(A) on the roll peripheral surface. On the roll peripheral surface of the pushing member 130, a plurality of pushing portions 131 continuing in the first direction D1 are arranged at intervals in the second direction D2 as shown in Fig. 10, for example. Between the pushing portions 131, 131, a recess 132 continuing in the first direction D1 is formed. The pushing portion 131 of the pushing member 130 corresponds to the first recess 125A of the support body 120. The recess 132 of the pushing member 130 corresponds to the protrusion row 121A of the support body 120. The bottom of the recess 132 of the pushing member 130 has a structure that allows hot air to pass through, and for example, a plurality of holes (not shown) are provided therein.

[0072] The height of the pushing portion 131 of the pushing member 130 is preferably 1 mm or more so that it can be sufficiently inserted between the protrusions 121 of the support 120 .

[0073] The first direction D1 and the second direction D2 in the support 120 and the pushing member 130 are preferably a machine direction (MD) and a cross direction (CD) perpendicular to the machine direction in the manufacturing process. The machine direction and the cross direction in the manufacturing process preferably correspond to one direction Y and a direction X crossing the one direction Y in the nonwoven fabric 20, and preferably correspond to the longitudinal direction and the cross direction in an absorbent article including the nonwoven fabric 20. However, the first direction D1 and the second direction D2 are not limited to these.

[0074] In step (I), the protrusions 121 of the support 120 are inserted into the recesses 132 of the pushing member 130. The pushing portions 131 of the pushing member 130 are inserted into the first recesses 125A of the support 120 (FIGS. 8(A) and 11). This pushing between the support 120 (FIG. 9) and the pushing member 130 (FIG. 10) can favorably form the uneven shape of the first fiber layer M1. The first fiber web 100 is pressed into the first recess 125A of the support 120 by the pressing portion 131 of the pressing member 130 to form a shape. This portion becomes the rib portion 11 in the first fiber layer M1 of the nonwoven fabric 20. At this time, between the protrusion 121 of the support 120 and the pressing portion 131 of the pressing member 130, the fibers of the first fiber web 100 are shaped into a vertically standing shape along the thickness direction. The shaped fibers are not fused and have high mobility, so they are oriented in the thickness direction. This portion becomes the wall portion 11B of the rib portion 11 in the first fiber layer M1 of the nonwoven fabric 20. Meanwhile, at the positions of the protrusions 121 of the support 120, the fibers of the first fibrous web 100 are pushed up to the bottom of the recesses 132 of the pushing member 130 and opened. This portion becomes the open portion 3 of the bottom portion 12 of the first fiber layer M1 of the nonwoven fabric 20. The second recess 125C between the protrusions 121, 121 in the protrusion row 121A of the support 120 corresponds to the recess 132 of the pushing member 130, so the pushing portion 131 does not enter. However, the pushing force of the pushing portions 131, 131 of the pushing member 130 acts on both sides of the fibers of the first fiber web 100 in the second recess 125C of the protrusion row 121A. Due to this action, the fibers of the first fiber web 100 in the second recess 125C are stretched in the second direction D2 by the pushing portions 131, 131 on both sides and pushed in the thickness direction, so that the fibers are shaped in the thickness direction and the fiber orientation changes. This portion becomes the saddle portion 15 in the first fiber layer M1 of the nonwoven fabric 20. The saddle portion 15 has an apex 15A and a wall portion 15B, and the wall portion 15B is similar to the wall portion 11B of the ridge portion 11.

[0075] The height of the protrusions 121 of the support 120 and the height of the pushing portion 131 of the pushing member 130 are appropriately determined depending on the thickness of the nonwoven fabric to be manufactured, etc. For example, it is preferably 2 mm or more, more preferably 3 mm or more, even more preferably 5 mm or more, and preferably 50 mm or less, more preferably 40 mm or less, and even more preferably 30 mm or less. Specifically, it is preferably 2 mm or more and 50 mm or less, more preferably 3 mm or more and 40 mm or less, and even more preferably 5 mm or more and 30 mm or less.

[0076] Next, in step (II), after removing the pushing member 130 from the support 120, a first hot air W1 is blown onto the porous fiber web 101 to fuse the fibers together to obtain a porous nonwoven fabric 102 (FIG. 8(B)). This porous nonwoven fabric 102 becomes the first fiber layer M1 of the nonwoven fabric 20. For example, as shown in FIG. 8, after removing the pushing member 130 inserted into the support 120, the support 120 rotates while holding the porous fiber web 101, and after passing through the meshing portion between the support 120 and the pushing member 130, the first hot air W1 is blown onto the porous fiber web 101 at the position of the hot air blowing section 140 in FIG. 8(B), in the above step (II). The support 120 preferably has a hot air suction section 141 at a position facing the hot air blowing section 140 inside the drum.

[0077] The temperature of the first hot air W1 is set to a temperature capable of melting the thermoplastic fibers constituting the porous fibrous web 101 and forming fused fiber portions at the intersections of the fibers. Considering typical fiber materials used in this type of product, the temperature is preferably 0°C to 70°C higher than the melting point of the thermoplastic fibers constituting the porous fibrous web 101, and more preferably 5°C to 50°C higher. From the viewpoint of effective fusion, the wind speed of the first hot air W1 is preferably 1 m / s or more, and more preferably 2 m / s or more. Also, from the viewpoint of making the device scale compact, the wind speed of the first hot air W1 is preferably 100 m / s or less, and more preferably 80 m / s or less.

[0078] Next, in step (III), a second fibrous web 103 having constituent fibers with a smaller fiber diameter than the first fibrous web 100 is supplied and laminated on the open-hole side of the porous nonwoven fabric 102 (FIG. 8(C)). For example, the porous nonwoven fabric 102 formed by blowing the first hot air W1 is separated from the drum circumferential surface of the support 120 and transported downstream on a belt conveyer with the side on which the open holes 3 are formed by the protrusions 121 facing up, and the second fibrous web 103 is joined to the open-hole side and laminated.

[0079] Next, in step (IV), a second hot air W2 is blown in a fusion furnace 170 to fuse the fibers of the porous nonwoven fabric 102 and the second fibrous web 103 together and fuse the fibers in the second fibrous web 103 together (FIG. 8(D)). This integrates the porous nonwoven fabric 102 and the second fibrous web 103 and also turns the second fibrous web 103 into a nonwoven fabric. This nonwoven fabric of the second fibrous web 103 becomes the second fiber layer M2 of the nonwoven fabric 20. At this time, as shown in Fig. 8(D), the porous nonwoven fabric 102 is placed on the net 180 with the side facing down, and the second hot air W2 is blown onto the second fiber web 103, so that the second fiber web 103 is pressed in. The pressed second fiber web 103 enters the openings 3 of the porous nonwoven fabric 102 into the region partitioned by the walls 11B and 15B, and a protuberance 5 is formed. At the same time, the base portions 1D of the walls 11B and 15B of the porous nonwoven fabric 102 are integrated with the second fiber web 103 in the contact region with the second fiber web 103, forming fiber fusion portions at the intersections of the fibers. The walls 11B and 15B are also pressed into the second fiber web 103. This biting is caused by the second hot air W2, and is performed while the shapes of the walls 11B and 15B are maintained. Moreover, due to the blowing process of the second hot air W2, the shapes (heights) of the walls 11B and 15B are easily maintained, and in this state, the base portions 1D of the walls 11B and 15B are closely and integrally attached to the second fiber web 103. In this way, the second fiber layer M2 (the nonwoven product of the second fiber web 103) is closely attached to the entire surfaces (walls 11B, 15B, and apertures 3) of the uneven porous nonwoven fabric 102 (first fiber layer M1) and integrated therewith, thereby obtaining the nonwoven fabric 20 described above.

[0080] Taking into consideration the typical fiber materials used in this type of product, the temperature of the second hot air W2 is preferably 0°C to 70°C higher than the melting point of the thermoplastic fibers that make up the unevenly perforated nonwoven fabric 102 and the second fiber web 103, and more preferably 5°C to 50°C higher. The wind speed of the second hot air W2 is preferably 0.3 m / s or more, and more preferably 0.4 m / s or more, from the viewpoint of fusing the fibers in the second fibrous web 103 and from the viewpoint of sufficiently fixing the porous nonwoven fabric 102 and the second fibrous web 103. Moreover, from the viewpoint of further increasing the softness of the nonwoven fabric 20, the wind speed of the second hot air W2 is preferably 50 m / s or less, and more preferably 30 m / s or less.

[0081] In the above manufacturing method, the push-in member 130 is not limited to one having push-in portions 131 continuous in the first direction D1 as shown in Fig. 10. For example, the push-in portions 131 may be formed in a lattice shape, with square-shaped recesses 132 between the lattice-shaped push-in portions 131. In this case, the height of the saddle portion 15 to be formed becomes higher, and the unevenness becomes more distinct.

[0082] In the manufacturing method of the nonwoven fabric of this embodiment, it is preferable to have a cooling step after blowing the first hot air W1. For example, as shown in FIG. 8, it is preferable to arrange a cooling section 160 having a cooling nozzle and a cooling suction section 161 inside the drum of the support 120 opposite each other at a position where the porous nonwoven fabric 102 obtained by blowing the first hot air W1 is aligned along the outer periphery of the drum of the support 120. This makes it possible to keep the support 120 at a certain temperature or lower, and to peel off the obtained nonwoven fabric while maintaining its shape. As a result, in the manufactured nonwoven fabric 10 (20), the shapes of the walls 11B and 15B of the first fiber layer M1 are well maintained, and good cushioning properties, liquid permeability, and visibility of the open holes 3 can be improved.

[0083] The thermoplastic fibers constituting the nonwoven fabric of the present invention can be any fibers commonly used as materials for nonwoven fabrics without any particular limitations. For example, they may be fibers made of a single resin component or composite fibers made of multiple resin components. Composite fibers may have, for example, a core-sheath structure or a side-by-side structure. When using composite fibers containing a low melting point component and a high melting point component as the thermoplastic fiber (for example, composite fibers having a core-sheath structure in which the sheath is a low melting point component and the core is a high melting point component), the temperature of the hot air blown onto the fiber web in the manufacturing process is preferably equal to or higher than the melting point of the low melting point component and lower than the melting point of the high melting point component. More preferably, the temperature is equal to or higher than the melting point of the low melting point component and 10°C lower than the melting point of the high melting point component, and even more preferably, the temperature is 5°C or higher than the melting point of the low melting point component and 20°C or lower than the melting point of the high melting point component. In terms of elasticity, the more the core of the core-sheath structure composite fibers have, the higher the elasticity. Therefore, it is preferable that the core component is larger in terms of cross-sectional area ratio. A specific example of a composite fiber having a core-sheath structure in which the sheath is a low melting point component and the core is a high melting point component is a composite fiber having a core-sheath structure in which the sheath is a polyethylene resin (hereinafter also referred to as PE) and the core is a polyethylene terephthalate resin (hereinafter also referred to as PET). Furthermore, in composite fibers with a core-sheath structure, when the resin component of the sheath has a lower glass transition point than the resin component of the core (hereinafter referred to as a low-glass transition point resin component; for example, the resin component of the core is PET and the resin component of the sheath is PE), the thickness recovery of the nonwoven fabric can be further improved by reducing the mass ratio of the low-glass transition point resin component.

[0084] The nonwoven fabric of the present invention can be used in various applications. For example, it can be used as a component of various absorbent articles. The various absorbent articles broadly include articles used to absorb liquids discharged from the body, such as diapers for adults and infants, sanitary napkins, panty liners, and urine pads.

[0085] An absorbent article having the nonwoven fabric of the present invention typically comprises a top sheet, a back sheet, and a liquid-retentive absorbent interposed between the two sheets. In the absorbent article, the nonwoven fabric of the present invention can be suitably used as the top sheet that contacts the wearer's skin.

[0086] In relation to the above-mentioned embodiments, the present invention further discloses the following nonwoven fabric and a method for producing the nonwoven fabric.

[0087] <1> A nonwoven fabric having a first fiber layer and a second fiber layer laminated in a thickness direction, the nonwoven fabric including fused fiber portions at intersections of the fibers, the first fiber layer and the second fiber layer are integrated by the fiber fusion portions between the fibers of each layer, the first fiber layer has a concave-convex structure including a plurality of protruding portions and a bottom portion provided between adjacent protruding portions, each of the plurality of protruding portions includes an apex portion and a wall portion supporting the apex portion, the wall portion extending perpendicularly to a planar direction of the nonwoven fabric, and the bottom portion has an opening portion penetrating in a thickness direction; The second fiber layer is provided on the side of the first fiber layer where the bottom portion is located, A nonwoven fabric for absorbent articles, wherein the constituent fibers of the second fiber layer have a smaller fiber diameter than the constituent fibers of the first fiber layer and are exposed to the side of the first fiber layer at the openings.

[0088] <2> The opening area of ​​the hole is 1.0 mm 2 More than 50mm 2 Less than or equal to 1.5 mm, preferably 2 More preferably, 2.0 mm 2 More than 40mm, preferably 2 Less than or equal to 35mm, preferably 2 The above-mentioned <1> The nonwoven fabric for absorbent articles according to claim 1.

[0089] <3> the second fiber layer has a protruding portion on a surface facing the first fiber layer, the protruding portion extending from the opening of the first fiber layer into the region defined by the wall portion; <1> or <2> The nonwoven fabric for absorbent articles according to claim 1. <4> The raised portion is visible from the side of the first fiber layer. <3> The nonwoven fabric for absorbent articles according to claim 1. <5> the bottom of the raised portion is connected to a contact area between the wall portion of the first fiber layer and the second fiber layer; <3> or <4> The nonwoven fabric for absorbent articles according to claim 1. <6> a valley formed by a base portion of the wall portion constituting the protrusion and the skirt portion of the protrusion portion extending to the base portion; <5> The nonwoven fabric for absorbent articles according to claim 1. <7> In the contact region of the wall portion of the first fiber layer with the second fiber layer, the fibers of the second fiber layer are oriented in a planar direction, and the fibers of the surface of the bottom of the protrusion have a fiber orientation different from that of the fibers of the wall portion. <3> ~ <6> 10. The nonwoven fabric for absorbent articles according to claim 9. <8> In a contact region between a base portion of the wall portion and the second fiber layer, the base portion is integrated with the second fiber layer by being embedded therein. <6> or <7> The nonwoven fabric for absorbent articles according to claim 1.

[0090] <9> the hydrophilicity of the fibers constituting the second fiber layer is higher than the hydrophilicity of the fibers constituting the first fiber layer; <1> ~ <8> 10. The nonwoven fabric for absorbent articles according to claim 9. <10> the difference (G1-G2) between the contact angle (G1) of the constituent fiber of the first fiber layer and the contact angle (G2) of the constituent fiber of the second fiber layer is 0.5 or more and 50.0 or less, preferably 1.0 or more, more preferably 2.0 or more, and is preferably 45.0 or less, more preferably 40.0 or less; <9> The nonwoven fabric for absorbent articles according to claim 1.

[0091] <11> the difference between the fiber diameter of the second fiber layer and the fiber diameter of the first fiber layer is 2 μm or more, preferably 3 μm or more, and more preferably 4 μm or more; <1> ~ <10> 10. The nonwoven fabric for absorbent articles according to claim 9. <12> The difference between the fiber diameter of the second fiber layer and the fiber diameter of the first fiber layer is 50 μm or less, preferably 40 μm or less, and more preferably 30 μm or less. <11> The nonwoven fabric for absorbent articles according to claim 1.

[0092] <13> the number of fibers per unit area of ​​the second fiber layer is greater than the number of fibers per unit area of ​​the top portion of the first fiber layer; <1> ~ <12> 10. The nonwoven fabric for absorbent articles according to claim 9. <14> The difference between the number of fibers per unit area of ​​the second fiber layer and the number of fibers per unit area of ​​the top of the first fiber layer is 5 or more and 190 or less, preferably 8 or more, more preferably 10 or more, and is preferably 185 or less, more preferably 180 or less. <13> The nonwoven fabric for absorbent articles according to claim 1.

[0093] <15> The second fiber layer has a surface facing the first fiber layer, and the surface facing the first fiber layer is a continuous fiber layer extending in a planar direction. <1> ~ <14> 10. The nonwoven fabric for absorbent articles according to claim 9.

[0094] <16> The first fiber layer has a fiber fusion portion at an intersection between the fiber of the wall portion and the fiber of the second fiber layer in a contact region between the wall portion and the second fiber layer. <1> ~ <15> 10. The nonwoven fabric for absorbent articles according to claim 9. <17> The second fiber layer in the contact region is formed as a recess by being bitten into by the wall portion, and the first fiber layer and the second fiber layer are integrated in the recess of the contact region by the fused fiber portion. <16> The nonwoven fabric for absorbent articles according to claim 1.

[0095] <18> The ratio of the thickness of the raised portion to the thickness of the first fiber layer is 0.05 or more and 0.9 or less, preferably 0.10 or more, more preferably 0.15 or more, and preferably 0.8 or less, more preferably 0.7 or less. <1> ~ <17> 10. The nonwoven fabric for absorbent articles according to claim 9. <19> In the first fiber layer, a hollow region is formed between the first fiber layer and the second fiber layer inside the protrusion. <1> ~ <18> 10. The nonwoven fabric for absorbent articles according to claim 9.

[0096] <20> Weight is 20g / m 2 More than 100g / m 2 The above-mentioned <1> ~ <19> 2. The nonwoven fabric for absorbent articles according to any one of claims 1 to 11. <21> 4.9mN / cm 2 The thickness under load is 0.8 mm or more and 10 mm or less. <1> ~ <20> 10. The nonwoven fabric for absorbent articles according to claim 9. <22> The fibers of the wall are longitudinally oriented. <1> ~ <21> 10. The nonwoven fabric for absorbent articles according to claim 9.

[0097] <23> The fibers of the wall portion have a longitudinal orientation ratio of 60% or more. <22> The nonwoven fabric for absorbent articles according to claim 1. <24> The fiber orientation on the surface of the skirt portion has a longitudinal orientation rate of less than 45%. <7> ~ <23> 10. The nonwoven fabric for absorbent articles according to claim 9. <25> In a plan view from one surface side, the convex portion of the first fiber layer includes a plurality of ridge portions extending in one direction Y and arranged at a distance from each other in a direction X intersecting the one direction Y, and a saddle portion connecting adjacent ridge portions. <1> ~ <24> 10. The nonwoven fabric for absorbent articles according to claim 9. <26> The saddle portion includes an apex portion on one side and a wall portion supporting the apex portion. <25> The nonwoven fabric for absorbent articles according to claim 1. <27> The above <1> ~ <26> An absorbent article comprising the nonwoven fabric for absorbent articles according to any one of the above.

[0098] <28> a pressing step of placing a first fiber web on a support having an uneven shape including a plurality of protrusions and recesses between the protrusions, pressing the first fiber web along the recesses with a pressing part of a pressing member to form a shape, and opening holes at locations corresponding to the protrusions, thereby forming an uneven open-hole fiber web having an open surface on the opposite side to the support; a step of removing the pushing member from the support, and then blowing a first hot air stream onto the porous fiber web to fuse the fibers together to obtain a porous nonwoven fabric; supplying a second fibrous web having constituent fibers with a smaller fiber diameter than that of the first fibrous web, and laminating the second fibrous web on the porous surface side of the porous uneven nonwoven fabric; A method for manufacturing a nonwoven fabric for absorbent articles, comprising a heat fusing process in which a second hot air is blown to fuse the fibers of the uneven nonwoven fabric and the second fibrous web together, and to fuse the fibers in the second fibrous web together. EXAMPLES

[0099] The present invention will be described in more detail below based on examples, but the present invention is not limited thereto. In the examples, "parts" and "%" are all based on mass unless otherwise specified. "←" means that the value is the same as the value in the left column.

[0100] Example 1 Based on the production method shown in FIG. 8, the nonwoven fabric shown in FIGS. 4 to 7 was produced under the following conditions, and this was used as a nonwoven fabric sample of Example 1. The first fiber web 100 is made of thermoplastic fibers having a fiber diameter of 14 μm and a core-sheath type (polyethylene terephthalate (PET) (core): polyethylene (PE) (sheath) = 5:5 (mass ratio)) and a basis weight of 30 g / m 2 The second fiber web 103 was made of thermoplastic fibers having a fiber diameter of 12 μm and a core-sheath type (polyethylene terephthalate (PET) (core): polyethylene (PE) (sheath) = 5:5 (mass ratio)) with a basis weight of 40 g / m 2 The fiber web was obtained as follows. In the support 120, the MD pitch of the projections 121 including the spires 122 in plan view was 5 mm, the CD pitch was 5 mm, and the projection height including the spires 122 was 3.5 mm. The planar shape of the projections 121 from the spire 122 side was square. The CD pitch of the pushing portion 131 of the pushing member 130 was 5 mm, and the pushing portion height was 6 mm. The temperature of the first hot air W1 was 160°C, and the wind speed was 3.0 m / sec. In this way, an unevenly open nonwoven fabric 102 (first fiber layer M1) having open portions 3 with the pore area shown in Table 1 was produced. The temperature of the second hot air applied to the second fiber web 103 laminated on the open-pore side of the unevenly open-pore nonwoven fabric 102 was 160° C., and the air speed was 1.3 m / sec. In this way, a nonwoven fabric sample of Example 1 having the shape shown in Figs. 4 to 7 was produced.

[0101] In the nonwoven fabric sample of Example 1 produced, the walls 11B and 15B of the first fiber layer M1 extended vertically, and the fibers were longitudinally oriented. The fibers constituting the second fiber layer M2 had a smaller fiber diameter than the fibers constituting the first fiber layer M1 as shown in Table 1, and were exposed to the first fiber layer side at the openings 3. The difference in fiber diameter of the fibers constituting the first fiber layer M1 and the second fiber layer M2, the difference in the number of fibers per unit area, and the hydrophilicity of the fibers constituting the first fiber layer M1 and the second fiber layer M2 were as shown in Table 1. The second fiber layer M2 had a protrusion 5 extending from the openings 3 into the area partitioned by the walls 11B and 15B. The hydrophilicity of the nonwoven fabric sample of Example 1 was 4.9 mN / cm 2 (0.05gf / cm 2 ) The thickness under load was 6.0 mm.

[0102] Example 2 A nonwoven fabric sample of Example 2 was prepared in the same manner as in Example 1, except that the fiber diameters of the constituent fibers of the first fibrous web 100 and the second fibrous web 103 were set as shown in Table 1.

[0103] Example 3 A nonwoven fabric sample of Example 3 was prepared in the same manner as in Example 1, except that the fiber diameters of the constituent fibers of the first fibrous web 100 and the second fibrous web 103 were set as shown in Table 1.

[0104] Comparative Example 1 The two-layer nonwoven fabric described in Example 1 of Patent Document 2 was prepared as a nonwoven fabric sample for Comparative Example 3. The first fiber layer M1, which is the outer fiber layer on the first side, and the second fiber layer M2, which is the outer fiber layer on the second side, had the respective structures shown in Table 1. The nonwoven fabric sample for Comparative Example 3 did not have open holes 3 in the first fiber layer M1.

[0105] Comparative Example 2 A single-layer nonwoven fabric as described in Example 1 of Patent Document 1 was prepared, and a flat nonwoven fabric was bonded to the open-hole side of the nonwoven fabric by spirally coating a hot-melt adhesive. The coating weight of the adhesive was 12 g / m 2 The configurations of the single-layer nonwoven fabric and the flat nonwoven fabric were as shown in the items of the first fiber layer M1 and the second fiber layer M2 in Table 1.

[0106] Comparative Example 3 The uneven nonwoven fabric used as the surface material of a Merry's S size (Kao Corporation, manufactured in 2021) was peeled off, and a flat nonwoven fabric was bonded to the non-skin side of the uneven nonwoven fabric by spirally coating it with a hot melt adhesive. The coating weight of the adhesive was 12 g / m 2 The structures of the concave-convex nonwoven fabric and the flat nonwoven fabric were as shown in the items of the first fiber layer M1 and the second fiber layer M2 in Table 1.

[0107] The nonwoven fabric samples of each of the Examples and Comparative Examples were subjected to the following tests (1) to (3).

[0108] (1) Compressive deformation amount The compression characteristics were evaluated up to 5.0 kPa using KES-FB3 (product name) manufactured by Kato Tech Co., Ltd., in normal mode except for the terminal speed, which was set to 0.1 mm / s. The amount of deformation from 0.15 kPa to 2.5 kPa was then taken as the "compressive deformation amount" of each nonwoven fabric sample. Elasticity and cushioning were evaluated based on the "compressive deformation amount." The larger this value, the less likely it is to be crushed in the compression direction with a small load, and similarly, the more elastic it is. Also, the larger the value, the more likely it is to be crushed up to a load of 2.5 kPa, and the larger the value, the more likely it is to be deformed when touched, and therefore the more likely it is to feel cushioning.

[0109] (2) Visibility A commercially available baby diaper (product name "Merry's Smooth Air Through S Size", Kao Corporation, manufactured in 2020) with the top sheet removed was used as an absorbent core, and nonwoven fabrics cut to 100 x 250 mm from each nonwoven fabric sample of the examples and comparative examples were laminated. The nonwoven fabrics were laminated so that the second fiber layer side faced the absorbent core side, and the periphery of the laminated nonwoven fabrics was fixed to prepare a diaper for evaluation. The clarity of the openings was evaluated by three researchers (in their 20s and 30s) engaged in research and development of nonwoven fabrics, who performed a sensory evaluation on a five-point scale to determine whether clear openings were formed in the nonwoven fabric (top sheet), and the average value was compiled. The sensory evaluation was performed by leaving the diaper for evaluation stationary and visually observing the nonwoven fabric from above. Here, an average score of 3.5 points or more, preferably 4.0 points or more, is considered to indicate that the protuberance 5 is visible from the side of the first fiber layer M1.

[0110] (Sensory evaluation criteria) 5: It appears as though clear openings have been formed in the recesses throughout the entire surface sheet. 4: The impression is that there is a mixture of clear and unclear openings in the recesses throughout the entire surface sheet. 3: The impression is that unclear openings have been formed throughout the entire top sheet. 2: Only some of the recesses in the top sheet have unclear openings, and most of the openings seem not to have been formed. 1: It seems as though no holes have been formed in the recesses of the top sheet.

[0111] (3) Liquid absorbency (1-1) Preparation of artificial loose stool The artificial soft stool was prepared by mixing 15% bentonite (Kanto Chemical Co., Ltd., product number: 04066-01, standard: Grade 1 deer), 0.3% Poise 530 (Kao Corporation), 1.7% Emulgen 130K (Kao Corporation), and 83% ion-exchanged water using a digital mixer until the viscosity reached 40 cP (B-type viscometer: Toki Sangyo Co., Ltd., TVB-10M). (1-2) Testing the absorption rate of soft stool using simulated soft stool Each nonwoven fabric sample of the examples and comparative examples was placed on an absorbent body from which the surface material of Merry's S size (manufactured by Kao Corporation in 2021) had been peeled off to prepare a diaper sample. Each diaper sample was unfolded and spread out so that it was flat, and 10 g of simulated soft stool was injected at a flow rate of 6 g / s at a position 30 mm behind the center of the longitudinal direction of each diaper sample. The time it took for the simulated soft stool to be completely absorbed (the time it took for the stool to penetrate through the diaper surface and the surface material to be exposed) was measured and used as the soft stool absorption rate. The measurement was performed three times, and the average value was used as the soft stool absorption rate. (1-3) Surface loose stool flow test using simulated loose stool Each diaper sample was spread out in an unfolded state on the slope of a slope table with a slope angle of 20 degrees, and 10 g of simulated soft stool (viscosity 40 mPa s) was injected at a flow rate of 6 g / s from a position 30 mm rearward from the centre of the longitudinal direction Y of each diaper sample and 10 mm above the top sheet. After 30 seconds, the distance that the simulated loose stool flowed from the injection point on the top sheet was measured and this was taken as the loose stool flow distance. The measurement was performed three times, and the average value was taken as the loose stool flow distance. (1-4) Loose stool diffusion area test using simulated loose stool After conducting the same test as in (1-3), the area where the simulated loose stool was spread on the top sheet was transferred to an OHP sheet, scanned, and imported into Image-Pro to calculate the loose stool spreading area. The measurement was performed three times, and the average value was taken as the loose stool spreading area.

[0112] [Table 1]

[0113] As shown in Table 1, the nonwoven fabric samples of each Example had a larger amount of compression deformation and better cushioning than the nonwoven fabric samples of each Comparative Example. At the same time, the nonwoven fabric samples of each Example had a shorter soft stool absorption time, a shorter soft stool flow distance, and a smaller soft stool diffusion area than the nonwoven fabric samples of each Comparative Example, suppressing the spread of liquid and realizing quick absorption, and thus exhibiting excellent liquid absorbency. In addition, the nonwoven fabric samples of each Example had a higher visibility of the openings 3 than the nonwoven fabric samples of each Comparative Example, making it easier for the user to recognize the good liquid absorbency through the openings 3. [Explanation of symbols]

[0114] M1 First fiber layer M2 2nd fiber layer 1 Convex part 1A Top 1B Wall section 1D Base 2 bottom 3 Opening part 5 Protuberance 10, 20 Nonwoven fabric 10T, 20T One side 10B, 20B other side

Claims

1. An air-through nonwoven fabric having a first fiber layer and a second fiber layer laminated in the thickness direction, and including fiber fusion portions at intersections of fibers, The first fiber layer and the second fiber layer are integrated by the fiber fusion portions between the fibers of each other, The first fiber layer has an uneven structure including a plurality of convex portions and bottoms provided between adjacent convex portions. Each of the plurality of convex portions includes a top portion and a wall portion that supports the top portion. The wall portion extends perpendicular to the plane direction of the air-through nonwoven fabric, and an opening portion penetrating in the thickness direction is disposed in the bottom portion. The second fiber layer is provided on the side where the bottom portion of the first fiber layer is located, The constituent fibers of the second fiber layer have a smaller fiber diameter than the constituent fibers of the first fiber layer and are exposed on the side of the first fiber layer in the opening portion. An air-through nonwoven fabric for absorbent articles.

2. The air-through nonwoven fabric for absorbent articles according to claim 1, wherein the area of the opening portion is 1.0 mm 2 or more and 50 mm 2 or less.

3. The air-through nonwoven fabric for absorbent articles according to claim 1 or 2, wherein the second fiber layer has a raised portion that enters a region partitioned by the wall portion from the opening portion of the first fiber layer on the side facing the first fiber layer.

4. The air-through nonwoven fabric for absorbent articles according to claim 3, wherein the raised portion is visible from the side of the first fiber layer.

5. In the contact region between the wall portion in the first fiber layer and the second fiber layer, the fibers of the second fiber layer are oriented in the plane direction, and the fibers on the surface of the base portion of the raised portion have a fiber orientation different from that of the fibers of the wall portion. The air-through nonwoven fabric for absorbent articles according to claim 3.

6. The air-through nonwoven fabric for absorbent articles according to claim 3, wherein the ratio (H2 / H1) of the thickness H2 of the raised portion to the thickness H1 of the first fiber layer is 0.05 or more and 0.9 or less.

7. The hydrophilicity of the constituent fibers of the second fiber layer is higher than that of the constituent fibers of the first fiber layer. The air-through nonwoven fabric for absorbent articles according to claim 1 or 2.

8. The difference between the fiber diameter of the constituent fibers of the second fiber layer and the fiber diameter of the constituent fibers of the first fiber layer is 2 μm or more. The air-through nonwoven fabric for absorbent articles according to claim 1 or 2.

9. The number of fibers per unit area of the second fiber layer is larger than the number of fibers per unit area at the top of the first fiber layer. The air-through nonwoven fabric for absorbent articles according to claim 1 or 2.

10. The side of the second fiber layer facing the first fiber layer is a continuous fiber layer extending in the planar direction. The air-through nonwoven fabric for absorbent articles according to claim 1 or 2.

11. In the contact area between the wall portion in the first fiber layer and the second fiber layer, there is a fiber fusion portion at the intersection of the fibers of the wall portion and the fibers of the second fiber layer. The air-through nonwoven fabric for absorbent articles according to claim 1 or 2.

12. The basis weight is 20 g / m ２ or more and 100 g / m ２ or less. The air-through nonwoven fabric for absorbent articles according to claim 1 or 2.

13. 4.9 mN / cm ２ The thickness under load is 0.8 mm or more and 10 mm or less. The air-through nonwoven fabric for absorbent articles according to claim 1 or 2.

14. In a plan view from one side, as the convex portions of the first fiber layer, a plurality of ridge portions extending in one direction Y and spaced apart from each other in a direction X intersecting the one direction Y, and having a saddle portion connecting adjacent ridge portions. The air-through nonwoven fabric for absorbent articles according to claim 1 or 2.

15. An absorbent article having the air-through nonwoven fabric for absorbent articles according to claim 1 or 2.

16. Place the first fiber web on a support having a concavo-convex shape with a plurality of protrusions and recesses between the protrusions, and along the recesses, push the first fiber web into the recesses by the pushing portion of a pushing member to shape it, and open holes at positions corresponding to the protrusions to form a concavo-convex perforated fiber web having a perforated surface on the side opposite to the support, a pushing step; After removing the pushing member from the support, blow first hot air onto the concavo-convex perforated fiber web to fuse the fibers together to obtain a concavo-convex perforated air-through nonwoven fabric; Supply a second fiber web having a smaller fiber diameter of constituent fibers than the first fiber web and laminate it on the perforated surface side of the concavo-convex perforated air-through nonwoven fabric; A method for manufacturing an air-through nonwoven fabric for absorbent articles, comprising a heat fusion step of blowing second hot air to fuse the fibers of the concavo-convex perforated air-through nonwoven fabric and the second fiber web together and to fuse the fibers in the second fiber web together.

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