Nonwoven fabric for absorbent article

Abstract

To provide a nonwoven fabric for absorbent article capable of increasing visibility at apertures disposed at bottom parts of an uneven structure.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 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. 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. The second fiber layer has raised parts entering a region partitioned by the wall part from the aperture of the first fiber layer on a side of a surface facing the first fiber layer.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, sanitary napkins, etc. For example, nonwoven fabrics used as topsheets of absorbent articles include those with various structures. For example, Patent Document 1 describes a nonwoven fabric having a concave-convex structure with a plurality of ridges and a bottom with holes at the bottom as a top sheet of an absorbent article. Patent Document 2 describes a nonwoven fabric having a first nonwoven fabric layer and a second nonwoven fabric layer laminated together. The first nonwoven fabric layer has a concave-convex structure, and the second nonwoven fabric layer has a substantially flat shape. [Prior art documents] [Patent documents]

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

[0004] When a nonwoven fabric having an opening at the bottom of the concave-convex structure is used as a top sheet of an absorbent article, the presence of the opening can enhance the liquid absorbency of the absorbent article. The opening includes a hole penetrating in the thickness direction and a hole having a concave bottom. The high liquid absorbency is easily understood by a user who picks up the absorbent article by recognizing the opening structure. However, when the nonwoven fabric is incorporated into an absorbent article as a topsheet, the openings are difficult to see due to the presence of the underlying member, and therefore, from the viewpoint of appealing to users of high liquid absorbency, it is desirable for the openings at the bottom of the nonwoven fabric to be highly visible.

[0005] In view of the above, the present invention relates to a nonwoven fabric for absorbent articles that can improve the visibility of openings arranged at the bottom of a concave-convex structure. [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 the intersections of fibers, wherein the first fiber layer has an uneven structure including a plurality of protrusions and a bottom portion provided between adjacent protrusions, each of the plurality of protrusions has a top portion and a wall portion supporting the top portion, and the bottom portion has an opening portion penetrating through in the thickness direction, the second fiber layer is provided on the side of the first fiber layer on which the bottom portion is located, and the second fiber layer has a raised portion, on the side facing the first fiber layer, which extends from the opening portion of the first fiber layer into an area partitioned by the wall 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, 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 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 enhance the visibility of the openings arranged at the bottom of the uneven structure. According to the manufacturing method of the nonwoven fabric for absorbent articles of the present invention, the above-mentioned 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] 1A is a cross-sectional view showing a laminate in which an example of a nonwoven fabric for absorbent articles of this embodiment is placed on an absorbent body, and FIG. 1B is a photograph of the laminate of FIG. 1A taken from the side of the nonwoven fabric for absorbent articles. [Diagram 3] (A) is a cross-sectional view showing a schematic diagram of a laminate in which a conventional nonwoven fabric for absorbent articles is placed on an absorbent body, and (B) is a photograph taken from the side of the nonwoven fabric for absorbent articles of the laminate in (A). [Figure 4] (A) is a cross-sectional view showing a schematic diagram of a laminate in which another conventional example of a nonwoven fabric for absorbent articles is placed on an absorbent body, and (B) is a photograph taken from the side of the nonwoven fabric for absorbent articles of the laminate of (A). [Diagram 5] 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. [Figure 6] 6 is a cross-sectional view taken along the line R1-R1 of the nonwoven fabric for absorbent articles shown in FIG. 5. [Figure 7] 6 is a cross-sectional view taken along the line R2-R2 of the nonwoven fabric for absorbent articles shown in FIG. 5. [Figure 8] 6 is a cross-sectional view taken along the line R3-R3 of the nonwoven fabric for absorbent articles shown in FIG. 5. [Figure 9] 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 10] FIG. [Figure 11] FIG. [Figure 12] FIG. 13 is a plan view showing a state in which the support body and the push-in member are combined. [Figure 13] 10(A) is a photograph substituting a drawing showing an example of a thickness direction cross section of a nonwoven fabric obtained by the manufacturing method of the nonwoven fabric for absorbent articles of the present embodiment shown in FIG. 9, and FIG. 10(B) is a photograph substituting a drawing showing an example of a thickness direction cross section of a nonwoven fabric for absorbent articles obtained by a conventional manufacturing method in which a nonwoven fabric is laminated and integrated with an unevenly perforated nonwoven fabric. [Figure 14] 14 is a photograph showing a partially enlarged cross section shown in FIG. 13(A). [Figure 15] 14 is a photograph showing a partially enlarged cross section shown in FIG. 13(B). 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 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. For example, when the nonwoven fabric 10 is used as a top sheet of an absorbent article, the one side 10T can be used as the skin side. In this case, the first fiber layer M1 is also called the upper layer, and the second fiber layer M2 is also called 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] An end portion (also referred to as a root portion 1D) of the other surface side 10B of the wall portion 1B abuts against the second fiber layer M2. In a contact region 4 between 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. From the viewpoints 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 fused fiber 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 vertically with respect to the plane of the other surface 10B of the nonwoven fabric 10 (the second fiber layer M2). This vertical orientation of the fibers increases the support force of the wall 1B in the thickness direction with respect to the top 1A and the second fiber layer M2, and makes it easier for the thickness of the protruding portion 1 of the nonwoven fabric 10 to be maintained even under load. As a result, the nonwoven fabric 10 including the first fiber layer M1 and the second fiber layer M2 is more likely to retain its thickness, and has excellent cushioning properties in combination with the elasticity due to the fiber structure of the fiber layers. 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 action of permeation of bodily fluids 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 1B acting in this way can be well maintained by being integrated with the second fiber layer M2 at the fused fiber parts described above with high strength. In addition, since this integration utilizes the bonded state at the intersections of the fibers at the fused fiber parts, there is no need to collapse the lower part of the wall 1B to ensure a bonding surface, as in the case of bonding with a conventional hot melt adhesive or the like. This allows the wall 1B to maintain a sufficient height.

[0016] The longitudinal orientation of the fibers in the wall portion 1B means that many of the fibers are aligned along the thickness direction Z of the first fiber layer M1, and that the longitudinal orientation ratio 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 ratio, but from the viewpoint of creating intersections between fibers to form fusion points and forming columns between the fibers to form a structure that can withstand force, it is preferable that the longitudinal orientation ratio 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 of the first fiber layer M1 and 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 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 having a cross section in the thickness direction 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 (the 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, 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 where wall 1B does not exist is defined as the thickness of the end portion of top 1A, and the portion excluding this thickness is defined as wall 1B.

[0019] 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.

[0020] 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 larger 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.

[0021] The 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 area of ​​the opening 3 is 50 mm 2 Less than 40mm is preferable 2 Less than or equal to 35mm is preferred 2 The following is even more preferred:

[0022] 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, and a rectangle.

[0023] The second fiber layer M2 is disposed on the side where the bottom of the first fiber layer M1 is located, and has a raised portion 5 on the surface facing the first fiber layer M1, which extends from the opening 3 of the first fiber layer M1 into the region defined by the wall portion 1B. That is, the raised portion 5 is located on one surface side 10T of the base portion 1D of the wall portion 1B in the contact region 4, and is in the space between the protrusions 1, 1 of the first fiber layer M1 and sandwiched by the wall portion 1B. On the other hand, the second fiber layer M2 in the contact region 4 adjacent to the raised portion 5 forms a recessed portion 6 due to being bitten into by the wall portion 1B.

[0024] 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 in which the degree of fiber orientation changes discontinuously between the two portions, which further emphasizes this shadow. Because the protrusions 5 are visible from the side of the first fiber layer M1, consumers of an absorbent article having the nonwoven fabric 10 as a topsheet can visually see that the nonwoven fabric has clear openings. As a result, consumers can be assured that the absorbent article has excellent liquid absorbency and can use the article with peace of mind. 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, this is not limiting, 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 via the fiber layer around the opening 3 in the inter-protrusion recess 2U, forming the valley and the dividing line.

[0025] 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. This can be seen, for example, by comparing the state of the open holes from the nonwoven fabric side (one surface side 10T) of an absorbent body in which a nonwoven fabric is placed as a topsheet, as shown in Figures 2 to 4. Figures 2 to 4 show the results of imaging at the same imaging position and angle, and the same lighting position and angle, with only the nonwoven fabric used as the topsheet being different. The nonwoven fabric used as the topsheet in Figure 2 is a nonwoven fabric 10S, an example of the nonwoven fabric 10 of this embodiment. The nonwoven fabric used as the topsheet in Figure 3 is a conventional nonwoven fabric C1 consisting only of a first fiber layer M1 that does not have open holes 3. The nonwoven fabric used as the topsheet in Figure 4 is a conventional nonwoven fabric C2 consisting only of a first fiber layer M1 having open holes 3. In the example nonwoven fabric 10S of this embodiment shown in Figure 2, the shadows around the openings 3 when viewed from the side of the first fiber layer M1 (one surface side 10T) are clearly more emphasized than those shown in Figures 3 and 4, and the visibility of the openings 3 is greatly improved.

[0026] This visibility makes it easier for consumers 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. Furthermore, in the nonwoven fabric 10, the raised portions 5 of the second fiber layer M2 penetrating into the first fiber layer M1 facilitate smooth transfer of liquid from the first fiber layer M1 to the second fiber layer M2 through the openings 3. This further improves the liquid permeability of the topsheet in an absorbent article incorporating the nonwoven fabric 10 as a topsheet, further suppressing liquid return and making it difficult for liquid to remain on the skin.

[0027] 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.

[0028] From a similar 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 at the bottom 2 of the first fiber layer M1 is further emphasized.

[0029] 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 fibers on the surface of the raised portion 5 in a range of 2 mm in the planar direction from the base 1D toward the base 7. Specifically, the fiber orientation on the surface of the bottom 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 1B, making the above-mentioned shadow clearer. Here, the fibers on the surface of the bottom 7 having a fiber orientation different from that of the fibers in the wall 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.

[0030] (Method of measuring the longitudinal orientation rate of fibers on the surface of the hem portion 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.

[0031] The ratio (H2 / H1) of the thickness H2 of the protrusions 5 to the thickness H1 of the first fiber layer M1 is preferably 0.05 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 shadows. 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 With this load applied, the process can be carried out in the same manner as in the above-mentioned method for dividing the fiber layer of the wall portion 1B.

[0032] 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 is preferable. 2 Less than 85 g / m is more preferable. 2 The following is even more preferred:

[0033] 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 portion. 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 2 The 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.

[0034] The fiber diameter of the fibers in the second fiber layer M2 is preferably larger than that of the fibers in the first fiber layer M1, so that fibers thicker than those in the first fiber layer M1 are exposed as protrusions 5 from the openings 3 of the first fiber layer M1, thereby improving the liquid permeability from the openings 3. From this viewpoint, the ratio (D2 / D1) of the fiber diameter (D2) of the second fiber layer M2 to the fiber diameter (D1) of the first fiber layer M1 is preferably 1.2 or more, more preferably 1.5 or more, and even more preferably 2.0 or more. From the viewpoint of improving the texture of the raised portions 5 and enhancing the shading of the openings, the ratio (D2 / D1) is preferably 10.0 or less, more preferably 9.0 or less, and even more preferably 8.0 or less. Furthermore, within the range satisfying the above ratio (D2 / D1), the fiber diameter (D2) of the fibers in the second fiber layer M2 is preferably 15 μm or more, more preferably 20 μm or more, and even more preferably 25 μm or more, from the viewpoint of improving the liquid permeability from the openings 3. Moreover, the fiber diameter (D2) of the fibers in the second fiber layer M2 is preferably 80 μm or less, more preferably 70 μm or less, and even more preferably 60 μm or less, from the viewpoint of improving the texture of the raised portions 5 and enhancing the shading of the openings. In the range satisfying the above ratio (D2 / D1), the fiber fineness (D1) of the first fiber layer M1 is preferably 8 μm or more, more preferably 10 μm or more, and even more preferably 12 μm or more from the viewpoint of obtaining a good texture. Also, the fiber diameter (D1) of the first fiber layer M1 is preferably 40 μm or less, more preferably 30 μm or less, and even more preferably 20 μm or less from the viewpoint of maintaining softness. The above fiber diameter means the average fiber diameter in each fiber layer.

[0035] (Method of measuring average fiber diameter in each fiber layer) 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 at a magnified scale using a scanning electron microscope (JCM-5100 manufactured by JEOL Ltd.) and adjusted to a magnification (300x) 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 fiber diameters of 30 fibers per photograph are measured, and the arithmetic average value is taken as the average fiber diameter in the present invention. When the fibers are not perfectly circular, the line segment that connects two points on the periphery in the cross section and has the maximum across length in the cross section is defined as the long axis, and the line segment that is perpendicular to the long axis and has the maximum length is defined as the short axis. The lengths of the long axis and the short axis of each fiber are then measured by analyzing and calculating them using image analysis software or the like, and the arithmetic mean value of the long axis length and the short axis length of a single fiber is defined as the fiber diameter of each fiber, and the arithmetic mean value of the fiber diameters of 30 fibers is defined as the average fiber diameter of the fibers in 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.

[0036] Next, a more preferred embodiment of the uneven structure described above in the nonwoven fabric 10 of this embodiment will be described.

[0037] The wall 1B of the first fiber layer M1 preferably has a shape extending perpendicular to the plane of the other surface 10B of the nonwoven fabric 10 (second fiber layer M2). When the wall 1B has a perpendicular wall surface, the valley between the protrusion 5 at the base 1D of the wall 1B becomes narrower and the shadow becomes stronger. In addition, the shadow can be recognized as being raised from the perpendicular wall 1B. This further improves the visibility of the openings 3. In addition, the vertical wall 1B vertically connects the top 1A and the second fiber layer M2, further enhancing the above-mentioned shading. It also strengthens the above-mentioned effect of the vertical orientation of the fibers. That is, the soft fiber layer of the top 1A is likely 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, making 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 down even when the protrusion 1 deforms under further pressure. Such excellent cushioning properties further improve the feel of the skin due to the above-mentioned uneven structure.

[0038] The "perpendicular" 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 of the nonwoven fabric 10. The angle θ means the intersection angle between the plane 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 including the convex portion 1, the angle θ means the interior angle among the angles 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.

[0039] 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 it is preferable that all of the walls 1B 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 viewpoints of further emphasizing the above-mentioned shadows in the nonwoven fabric 10 and making the above-mentioned effect of the longitudinal orientation of the fibers more effective.

[0040] In addition, it is preferable that the first fiber layer M1 has hollow regions 1C on the other surface side 10B of the protrusions 1. The hollow regions 1C are spaces that are not substantially filled with the fibers of the nonwoven fabric 10. Specifically, the hollow regions 1C have a fiber density of 10 fibers / mm 2 or less, as determined by the method described below. 2 The lower the fiber density in the hollow region 1C, the better. Furthermore, it is preferable from the viewpoint of improving liquid permeability that the raised portions 5A of the second fiber layer M2 also penetrate into the hollow regions 1C of the first fiber layer M1.

[0041] (Method of measuring fiber density) The fiber density can be measured by observing the cross section of the nonwoven fabric 10 using the following method. The nonwoven fabric 10 is cut in the thickness direction so as to pass through the area to be measured (for example, between the wall portions 1B). The cut surface is magnified and observed using a scanning electron microscope (JCM-6000Plus (product name) manufactured by JEOL Ltd.), and the number of cut fiber cross sections within a certain area of ​​the cut surface is counted. The magnification for the magnified observation is adjusted to a magnification (150x or more and 500x or less) that allows the measurement of approximately 30 to 60 fiber cross sections. Next, a 1mm 2 This is converted into the number of fiber cross sections per unit, and the fiber density (fibers / mm 2 The results of the measurements at three locations shall be averaged to determine the fiber density of the sample.

[0042] 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 against the skin. When the nonwoven fabric 10 is used 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, and can reduce the amount of liquid remaining on the skin contact side of the top sheet.

[0043] Next, a specific example (nonwoven fabric 20) of the nonwoven fabric 10 shown in Fig. 1 will be described with reference to Fig. 5 to Fig. 8. The nonwoven fabric 20 has the configuration described above for the nonwoven fabric 10. 5 to 8, 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 arranged at a distance from each other in a direction X intersecting the one direction Y. The other surface side 20B of the ribs 11 is formed as a hollow region 11C. 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 component 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.

[0044] 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.

[0045] 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, it is preferable that 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 the width direction X in FIG. 5), as shown in FIG. 6. Furthermore, the "vertical" of wall 11B refers to the interior angle between center line M of the width of the fiber layer of wall 11B and straight line L tangent to the surface of the other side 20B of nonwoven fabric 20 (second fiber layer M2) in a cross section perpendicular to the extending direction of rib 11 (thickness direction cross section at line R1-R1 along direction X intersecting with direction Y in FIG. 5), as shown in Fig. 6. This angle θ can be determined by observing a micrograph of the cross section along line R1-R1 obtained with the above-mentioned microscope.

[0046] 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-wise cross section at the position of line R2-R2 along one direction Y in FIG. 5) as shown in FIG. 7 in the same manner as the measurement method described above for wall portion 11B.

[0047] 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.

[0048] 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. 5, 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.

[0049] 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 in the portions where the saddle portions 15 are spaced apart. 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 and partitioned 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.

[0050] 5 to 8, in a plan view from one surface side 20T of the nonwoven fabric 20, the ridges 11 and saddles 15 are arranged in a lattice pattern, and the openings 3 of the bottom 12 are arranged in a square pattern scattered within the lattice. The raised portions 5 of the second fiber layer M2 extend from the openings 3 surrounded by the ridges 11 and saddles 15 into the lattice-shaped recessed spaces partitioned by the walls 11B and 15B. Since the raised portions 5 of the second fiber layer M2 are surrounded by the walls 11B and 15B in a lattice pattern in this manner, the shadows around the openings 3 are more 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.

[0051] 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 7 and 8. 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 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.

[0052] (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. 7, a thickness direction cross section (thickness direction cross section at the position of line R2-R2 in FIG. 5) of the nonwoven fabric 20 is prepared at the lowest position of the saddle portions 15 along the extension direction of the band region 16 in which the saddle portions 15 are arranged, and the fabric 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.

[0053] In addition, it is more preferable that the saddle portion 15 has a hollow region 15C as shown in FIG. 7 from the viewpoint of further promoting drainage of liquid to the other surface side 20B of the nonwoven fabric 20 when the nonwoven fabric 20 is used as a top sheet of an absorbent article. 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 promotes the diffusion of excreted liquid on the other surface side 20B of the nonwoven fabric 20, and further suppresses liquid retention on the one surface side 20T. As a result, the amount of liquid remaining in the nonwoven fabric 20 is further reduced, making it possible to further reduce the amount of liquid adhering to the skin.

[0054] Next, a preferred embodiment of a method for producing the nonwoven fabric 20 will be described with reference to Figures 9 to 12. The production method described below can also be applied to the production method for the nonwoven fabric 10. As shown in FIG. 9, 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 the second fiber web 103 and laminating it onto the open-pore 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.

[0055] 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 103 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.

[0056] In step (I), as shown in FIG. 9(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 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.

[0057] The support 120 is drum-shaped as shown in Fig. 9, for example, and has protrusions 121 as shown in Fig. 9(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. 10, 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. 10, 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.

[0058] 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).

[0059] The pushing member 130 is in the form of a roll as shown in Fig. 9, for example, and has a pushing portion 131 as shown in Fig. 9(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. 11, 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.

[0060] 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 projections 121 of the support 120 .

[0061] 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.

[0062] 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. 9(A) and 12). This pushing between the support 120 (FIG. 10) and the pushing member 130 (FIG. 11) 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.

[0063] 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. For example, it is preferably 2 mm or more, more preferably 3 mm or more, even more preferably 5 mm or more, and preferably 15 mm or less, more preferably 10 mm or less, and even more preferably 9 mm or less. Specifically, it is preferably 2 mm or more and 15 mm or less, more preferably 3 mm or more and 10 mm or less, and even more preferably 5 mm or more and 9 mm or less.

[0064] 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. 9(B)). This porous nonwoven fabric 102 becomes the first fiber layer M1 of the nonwoven fabric 20. For example, 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. 9(B). The support 120 preferably has a hot air suction section 141 at a position facing the hot air blowing section 140 inside the drum.

[0065] 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.

[0066] Next, in step (III), the second fibrous web 103 is supplied and laminated onto the open-hole side of the porous nonwoven fabric 102 (FIG. 9(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.

[0067] 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 to fuse the fibers in the second fibrous web 103 together (FIG. 9(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. 9(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 regions partitioned by the walls 11B and 15B, and the protuberances 5 are formed. At the same time, the walls 11B and 15B of the porous nonwoven fabric 102 are integrated with the second fiber web 103 in the contact regions with the second fiber web 103, forming fiber fusion parts at the intersections between 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 while the shapes (heights) are maintained, the walls 11B and 15B are closely and integrally attached to the second fiber web 103. In this manner, 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.

[0068] For example, as shown in the cross section of Fig. 13(A) (cross section at a position corresponding to Fig. 6), the first fiber layer M1 and the second fiber layer M2 can be formed so that the wavy shapes in the thickness direction are synchronized and are in full contact with each other. Even in full contact, the three-dimensional shape of the wall portion 11B is sufficiently maintained. At the same time, as shown in Fig. 14, in the above-mentioned contact state, the protrusions 5 of the second fiber layer M2 enter the area defined by the wall portion 11B through the openings 3 of the first fiber layer M1. In contrast, in a conventional manufacturing method different from the above, for example, a manufacturing method in which a first fiber layer M1 and a second fiber layer M2, which have been previously made into nonwoven fabrics, are laminated and then subjected to hot air treatment, even if treatment with the second hot air W2 is performed under the same conditions as in FIG. 13(A), the second fiber layer M2 does not enter the openings 3 as shown in the cross section of FIG. 13(B) (cross section at a position corresponding to FIG. 6) and FIG. 15. Moreover, the two layers are separated at that portion, generating gaps, and the shadows around the openings 3 are not emphasized. In another conventional manufacturing method, for example, a manufacturing method in which a first fiber layer M1 and a second fiber layer M2, which have been previously made into nonwoven fabrics, are integrated with a hot-melt adhesive or the like, it is necessary to collapse the lower part of the wall portion 11B to secure the adhesive surface, and it is difficult to maintain the shape of the wall portion 11B. Therefore, the nonwoven fabric of the present invention can be suitably produced by the method for producing a nonwoven fabric of this embodiment, which includes the above-mentioned steps (I), (II), (III) and (IV).

[0069] 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.

[0070] 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. 11. 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.

[0071] 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. 9, 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 20, the shapes of the walls 11B and 15B of the first fiber layer M1 can be well maintained, and good cushioning properties and better visibility of the open holes 3 can be achieved.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] In relation to the above-mentioned embodiments, the present invention further discloses the following nonwoven fabric and a method for producing the nonwoven fabric.

[0076] <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 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, and the bottom portion has an opening portion penetrating through the first fiber layer in a thickness direction; The second fiber layer is provided on the side of the first fiber layer where the bottom portion is located, The second fiber layer has a raised portion on the side facing the first fiber layer, the raised portion extending from the opening portion of the first fiber layer into the area partitioned by the wall portion.

[0077] <2> The raised portion is visible from the side of the first fiber layer. <1> The nonwoven fabric for absorbent articles according to claim 1. <3> 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> or <2> The nonwoven fabric for absorbent articles according to claim 1. <4> 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> ~ <3> 10. The nonwoven fabric for absorbent articles according to claim 9. <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; <1> ~ <4> 10. The nonwoven fabric for absorbent articles according to claim 9. <6> 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. <1> ~ <5> 10. The nonwoven fabric for absorbent articles according to claim 9.

[0078] <7> The surface of the top is a flat surface. <1> ~ <6> 10. The nonwoven fabric for absorbent articles according to claim 9. <8> The area of ​​the opening 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 35 mm, more preferably 2 The above-mentioned <1> ~ <7> 10. The nonwoven fabric for absorbent articles according to claim 9. <9> a valley formed by a base portion of the wall portion constituting the protrusion and a bottom portion of the protrusion portion extending to the base portion; <1> ~ <8> 10. The nonwoven fabric for absorbent articles according to claim 9. <10> the skirt portion is connected to a contact area between the wall portion of the first fiber layer and the second fiber layer; <9> The nonwoven fabric for absorbent articles according to claim 1. <11> 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. <9> or <10> The nonwoven fabric for absorbent articles according to claim 1. <12> 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, preferably 0.10 or more, more preferably 0.15 or more, and preferably 0.8 or less, more preferably 0.7 or less. <1> ~ <11> 10. The nonwoven fabric for absorbent articles according to claim 9. <13> The ratio (D2 / D1) of the fiber diameter (D2) of the fiber of the second fiber layer M2 to the fiber diameter (D1) of the fiber of the first fiber layer is 1.2 or more and 10.0 or less, preferably 1.5 or more, more preferably 2.0 or more, and preferably 9.0 or less, more preferably 8.0 or less. <1> ~ <12> 10. The nonwoven fabric for absorbent articles according to claim 9. <14> In the first fiber layer, a hollow region 1C is provided on the back side of the protrusion. <1> ~ <13> 10. The nonwoven fabric for absorbent articles according to claim 9.

[0079] <15> Weight is 20g / m 2 More than 100g / m 2 The above-mentioned <1> ~ <14> 2. The nonwoven fabric for absorbent articles according to any one of claims 1 to 11. <16> 4.9mN / cm 2 The thickness under load is 0.8 mm or more and 10 mm or less. <1> ~ <15> 10. The nonwoven fabric for absorbent articles according to claim 9.

[0080] <17> The fibers of the wall are longitudinally oriented. <1> ~ <16> 10. The nonwoven fabric for absorbent articles according to claim 9. <18> The fibers in the wall portion have a longitudinal orientation rate of 60% or more. <17> The nonwoven fabric for absorbent articles according to claim 1. <19> The fibers on the surface of the tail portion have a longitudinal orientation rate of less than 45%. <5> ~ <18> 10. The nonwoven fabric for absorbent articles according to claim 9. <20> The difference in longitudinal orientation rate between the fibers on the surface of the skirt portion and the fibers in the wall portion is 15% or more. <19> The nonwoven fabric for absorbent articles according to claim 1. <21> 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> ~ <20> 10. The nonwoven fabric for absorbent articles according to claim 9. <22> The saddle portion includes an apex portion on one side and a wall portion supporting the apex portion. <21> The nonwoven fabric for absorbent articles according to claim 1.

[0081] <23> The above <1> ~ <22> An absorbent article comprising the nonwoven fabric for absorbent articles according to any one of the above.

[0082] <24> 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 fiber web and laminating it 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

[0083] 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.

[0084] [Example 1] The nonwoven fabric shown in FIGS. 5 to 8 was produced by carrying out the following steps based on the production method shown in FIG. A first fiber web 100 was produced using thermoplastic fibers of a core-sheath type (polyethylene terephthalate (PET) / polyethylene (PE)=5:5) with a fineness of 1.3 dtex. The thermoplastic fibers had been subjected to a hydrophilization treatment. The first fiber web 100 was placed on a support 120, and a pushing member 130 was pushed into the support 120 from above the first fiber web 100 to perform a shaping treatment. A first hot air W1 was blown to perform a fusion treatment, and an unevenly perforated nonwoven fabric 102 (first fiber layer M1) was produced. The first hot air W1 had a temperature of 160° C. and a wind speed of 20 m / sec. The unevenly perforated nonwoven fabric 102 produced had a basis weight of 30 g / m 2 It was. Next, a second fiber web 103 made of core-sheath thermoplastic fibers having a fineness of 7.8 dtex was laminated on the porous surface side of the uneven porous nonwoven fabric 102, and a second hot air W2 was blown thereon to perform a fusion treatment to produce a laminated nonwoven fabric, which was used as a nonwoven fabric sample of Example 1. The second hot air W2 had a temperature of 160° C. and a wind speed of 2.0 m / sec. The nonwoven fabric sample of Example 1 produced had a basis weight of 70 g / m 2 In the nonwoven fabric sample of Example 1, the fibers of the wall portion 11B and the wall portion 15B of the first fiber layer M1 were longitudinally oriented. The second fiber layer M2 had protrusions 5 extending from the openings 3 into the region defined by the walls 11B and 15B.

[0085] [Comparative Example 1] A laminated nonwoven fabric was prepared in the same manner as in Example 1, except that in the support, the projections 121 had flat tips without perforations 122. This was used as a nonwoven fabric sample for Comparative Example 1. The nonwoven fabric sample of Comparative Example 1 did not have any openings 3 in the first fiber layer M1, and did not have any protrusions 5 in the second fiber layer M2 that extended into the first fiber layer M1.

[0086] [Comparative Example 2] A nonwoven fabric sample of Comparative Example 2 was produced in the same manner as in Example 1, except that the second fibrous web 103 was not laminated and the sample consisted only of the unevenly apertured nonwoven fabric 102 (first fibrous layer M1).

[0087] The structures of the nonwoven fabric samples of the Examples and Comparative Examples were examined. Specifically, the basis weight, thickness, angle of the wall 11 and the wall 15 (the angle between the extending direction of the wall 11 and the wall 15 and the plane of the other side 10B of the nonwoven fabric sample), and the longitudinal orientation ratio of the wall 11, the wall 15 and the second fiber layer were measured by the following methods.

[0088] <Metsuke> The area and mass of the nonwoven fabric were measured after storing it for 24 hours or more in an environment of 23±2°C and a relative humidity of 50±5%. <Thickness> 4.9mN / cm on nonwoven fabric 2 (0.05gf / cm 2 The thickness was measured with a thickness measuring device under a load of 100 mm. A laser displacement meter manufactured by Omron Corporation was used as the thickness measuring device. Measurements were taken at 10 points, and the average value was calculated to determine the thickness.

[0089] <Angle of wall portion 11 and wall portion 15> According to the above-mentioned method (method for measuring the longitudinal orientation rate of fibers in wall portion 1B), cross sections of the fiber layer of wall portion 11 and wall portion 15 were prepared and microscopic photographs were taken, and the angle θ between the extension direction of wall portion 11 and wall portion 15 and the plane of the other side 10B of the nonwoven fabric sample was determined.

[0090] <Longitudinal orientation ratio of wall portion 11, wall portion 15 and second fiber layer> The longitudinal orientation ratios of the wall portion 11, the wall portion 15 and the second fiber layer were determined based on the above-mentioned method (method for measuring the longitudinal orientation ratio of fibers in the wall portion 1B).

[0091] Furthermore, the clarity of the openings (visibility of the openings), the liquid absorption time, the liquid flow distance, and the amount of liquid returning were measured for the nonwoven fabric samples of Example 1 and Comparative Examples 1 and 2. The measurement methods are shown below.

[0092] <Clarity of openings> 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.

[0093] (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.

[0094] <Liquid absorption time> Diapers for evaluation were prepared in the same manner as in the above <Clarity of Openings>. 2 A pressure load of 1017 mm was evenly applied to the nonwoven fabric. 2 Artificial urine (composition: urea 1.940% by mass, sodium chloride 0.795% by mass, magnesium sulfate 0.110% by mass, calcium chloride 0.062% by mass, potassium sulfate 0.197% by mass, Red No. 2 (dye) 0.010% by mass, water (96.886% by mass) was injected through the tube. 30 g of artificial urine was injected three times at 10 minute intervals, and the time (seconds) until the entire amount was absorbed was measured. The time when artificial urine could no longer be observed inside the tube was recorded as "the entire amount was absorbed." The above operation was performed three times, and the average of the three times was recorded as the liquid absorption time (seconds). The shorter the liquid absorption time, the easier it is for the liquid to penetrate into the interior. In other words, the liquid absorption ability is excellent.

[0095] <Liquid flow distance> A 10cm x 20cm sample was cut from each nonwoven fabric sample of the Examples and Comparative Examples to prepare an evaluation sample, which was then fixed on a 45 degree inclined mounting section via commercially available tissue paper. 2g of artificial urine was poured from a height of 10mm above the evaluation sample over 20 seconds, and the flow of the artificial urine was observed. The distance from the injection point on the perpendicular line to the point where the artificial urine was drawn into the evaluation sample was measured and taken as the liquid flow distance. The above operation was carried out three times, and the average value of the three measurements was taken as the liquid flow distance (mm). The shorter the liquid flow distance, the easier the liquid penetrates into the interior. In other words, the liquid drawability is excellent.

[0096] <Amount of liquid returning> Diapers for evaluation were prepared in the same manner as in the above <Clarity of Openings>. 30 g of colored artificial urine was poured into this absorbent article over 10 seconds at a position 165 mm from the abdominal edge in the longitudinal direction and at the center in the width direction. 10 minutes after the start of the pouring, 30 g was poured again. 10 minutes after the start of the second pouring, 30 g was poured again, for a total of 90 g of artificial urine. The temperature of the test atmosphere was room temperature (20±5°C), and the temperature of the artificial urine was room temperature (20±5°C). Ten minutes after the completion of the injection, ten sheets of Advantech filter paper No. 4A (100 mm x 100 mm, mass measurement W1) were stacked and placed on the nonwoven fabric with the injection point at the center. A pressure of 3.5 kPa was applied through a 5 mm thick, 100 mm x 100 mm acrylic plate, and the mass of the filter paper was measured after two minutes (W2), and the amount of liquid return was calculated according to the following formula (I). Amount of liquid returned (mg) = Mass of filter paper after pressure (W2) - Initial mass of filter paper (W1) The above procedure was carried out three times, and the average of the three measurements was taken as the amount of liquid returning (mg). The smaller the amount of liquid returning, the less likely it was to cause liquid returning, and the higher the evaluation.

[0097] [Table 1]

[0098] As shown in Table 1, the nonwoven fabric samples of the examples had an evaluation value for "distinctness of openings" that was more than three times higher than the nonwoven fabric samples of Comparative Examples 1 and 2, and the visibility of the openings located at the bottom of the uneven structure was improved. In addition, the nonwoven fabric samples of the Examples had shorter "liquid absorption time", shorter "liquid flow distance", and smaller "liquid return amount" than the nonwoven fabric samples of Comparative Examples 1 and 2, and therefore had improved liquid absorbency. From the above, it was found that the nonwoven fabric samples of the Examples had higher visibility of the openings, which appeal to users as to their high liquid absorbency, and were superior in actual liquid absorbency, compared to the nonwoven fabric samples of Comparative Examples 1 and 2. [Explanation of symbols]

[0099] M1 First fiber layer M2 2nd fiber layer 1 Convex part 1A Top 1B Wall section 1C hollow area 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 the fibers, 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 supporting the top portion. Openings penetrating in the thickness direction are arranged in the bottoms. The second fiber layer is provided on the side where the bottom of the first fiber layer is located. The second fiber layer has a raised portion entering a region partitioned by the wall portion from the opening of the first fiber layer on the side facing the first fiber layer, the 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 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 raised portion is visible from the side of the first fiber layer.

4. The air-through nonwoven fabric for absorbent articles according to Claim 1 or 2, wherein the side of the second fiber layer facing the first fiber layer is a continuous fiber layer extending in the plane direction.

5. The air-through nonwoven fabric for absorbent articles according to Claim 1 or 2, having a fiber fusion portion at an intersection of the fibers of the wall portion and the fibers of the second fiber layer in a contact region between the wall portion and the second fiber layer in the first fiber layer.

6. The air-through nonwoven fabric for absorbent articles according to Claim 1 or 2, wherein in a contact region between the wall portion and the second fiber layer in the first 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.

7. The air-through nonwoven fabric for absorbent articles according to Claim 1 or 2, 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. Claim 8. The ratio (D2 / D1) of the fiber diameter (D2) of the fibers of the second fiber layer to the fiber diameter (D1) of the fibers of the first fiber layer is 1.2 or more and 10.0 or less. The air-through nonwoven fabric for absorbent articles according to claim 1 or 2. Claim 9 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. Claim 10 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. Claim 11. In a plan view from one surface side, as the convex portions of the first fiber layer, together with a plurality of ridge portions extending in one direction Y and arranged spaced apart from each other in a direction X intersecting the one direction Y, it has a saddle portion connecting the adjacent ridge portions. The air-through nonwoven fabric for absorbent articles according to claim 1 or 2. Claim 12 An absorbent article having the air-through nonwoven fabric for absorbent articles according to claim 1 or 2. Claim 13 Place the first fiber web on a support having an uneven shape with a plurality of protrusions and recesses between the protrusions, and along the recesses, push in the first fiber web by the pushing portion of a pushing member to shape it, and open holes at locations corresponding to the protrusions to form an uneven open-hole fiber web having an open-hole surface on the side opposite to the support. A pushing step; After removing the pushing member from the support, blow a first hot air onto the uneven open-hole fiber web to fuse the fibers together to obtain an uneven open-hole air-through nonwoven fabric. A step; A step of supplying a second fiber web and laminating it on the open-hole surface side of the uneven open-hole air-through nonwoven fabric; A heat fusion step of blowing a second hot air to fuse the fibers of the uneven open-hole air-through nonwoven fabric and the second fiber web together, and also fuse the fibers in the second fiber web together. A method for manufacturing an air-through nonwoven fabric for absorbent articles having the steps.

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