Nonwoven fabric for absorbent article

Abstract

To provide a nonwoven fabric for absorbent article that enables a user to recall high level of loose stool absorptivity of an absorbent article and has high loose stool absorptive capacity.SOLUTION: There is provided a nonwoven fabric for an absorbent article including a first fiber layer and a second fiber layer that are laminated in a thickness direction and including fiber fused parts at intersections between fibers. The first fiber layer includes: a plurality of recessed parts each having a space part open toward a skin surface side; and aperture parts penetrating in a thickness direction between respective ones of the neighboring recessed parts. Each of the plurality of recessed parts includes: wall parts extending vertically with respect to a plane direction of the nonwoven fabric; and a bottom part. The second fiber layer is disposed on a non-skin surface side of the first fiber layer and has protruding parts approaching areas partitioned by the wall parts from the aperture parts of the first fiber layer on an opposite surface side to 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 an uneven structure with vertical ridges and horizontal ridges whose fiber orientation directions are different from each other. Patent Document 2 describes a nonwoven fabric having an uneven structure with a plurality of ridges and a bottom, with openings arranged in the bottom, as a top sheet of an absorbent article. Patent Document 3 describes a nonwoven fabric in which a first nonwoven fabric layer and a second nonwoven fabric layer are laminated. The first nonwoven fabric layer has an uneven structure, and the second nonwoven fabric layer has a substantially flat shape. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-44320 A [Patent Document 2] JP 2020-467 A [Patent Document 3] 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 improve the liquid absorbency (particularly the absorbency of soft stool) of the absorbent article. The opening here includes a hole penetrating in the thickness direction and a hole having a concave bottom. This high absorbency of soft stool 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 top sheet, the openings are difficult to see due to the presence of the underlying member. Therefore, in order to appeal to users about the high soft stool absorbency, it is desirable for the above-mentioned nonwoven fabric to have high visibility of the openings at the bottom. Accordingly, it is desirable for the nonwoven fabric to further improve the soft stool absorbency that transfers the excrement to the absorbent body as the top sheet.

[0005] In view of the above, the present invention relates to a nonwoven fabric for absorbent articles which is capable of evoking high soft feces absorbency in absorbent articles and has high soft feces absorbency. [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 stacked in the thickness direction and includes fiber fusion portions at the intersections of the fibers, wherein the first fiber layer has a plurality of recesses with spaces open toward the skin side and openings penetrating in the thickness direction between adjacent recesses, each of the plurality of recesses having a wall portion extending perpendicular to the planar direction of the nonwoven fabric and a bottom portion, and the second fiber layer is arranged on the non-skin side of the first fiber layer and has a raised portion on the surface facing the first fiber layer that extends from the openings of the first fiber layer into an area partitioned by the wall portions.

[0007] The present invention also provides a pressing step of placing a first fiber web on a support having an uneven shape with 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 in the first fiber web at locations corresponding to the protrusions, thereby forming an unevenly perforated fiber web having an open surface on the opposite side to the support; and removing the pressing member from the support and then pressing the unevenly perforated fiber web. The present invention provides a method for producing a nonwoven fabric for absorbent articles, comprising the steps of: blowing a first hot air stream onto an ebb to fuse the fibers together and obtain a porous nonwoven fabric; supplying a second fibrous web and laminating the second fibrous web onto the side of the porous nonwoven fabric that has been pressed into the recesses of the support; and blowing a second hot air stream 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 be used to recall the high absorbency of soft feces in absorbent articles and has a high soft feces absorption capacity. 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] 2 is a partially enlarged cross-sectional view of the nonwoven fabric for absorbent articles shown in FIG. 1. [Diagram 3] 1 is a plan view showing a schematic view of a specific example of a nonwoven fabric for absorbent articles according to the present embodiment, viewed from the skin side. [Figure 4] 4 is a cross-sectional view taken along the line R1-R1 of the nonwoven fabric for absorbent articles shown in FIG. 3. [Diagram 5] 4 is a cross-sectional view taken along the line R2-R2 of the nonwoven fabric for absorbent articles shown in FIG. 3. [Figure 6] 4 is a cross-sectional view taken along the line R3-R3 of the nonwoven fabric for absorbent articles shown in FIG. 3. FIG. [Figure 7]4 is a cross-sectional view taken along line R4-R4 of the nonwoven fabric for absorbent articles shown in FIG. 3. [Figure 8] FIG. 1 is an explanatory diagram showing a schematic diagram of a preferred embodiment of the method for manufacturing a nonwoven fabric for absorbent articles according to the present invention, in which (A) shows a pushing process, (B) shows a process for obtaining an porous nonwoven fabric by a first hot air, (C) shows a process for laminating a second fibrous web onto the porous nonwoven fabric, and (D) shows a process for integrating the porous nonwoven fabric and the second fibrous web by a second hot air to form the second fibrous web into a nonwoven fabric. [Figure 9] FIG. [Figure 10] FIG. [Figure 11] FIG. 13 is a plan view showing a state in which the support body and the push-in member are combined. [Figure 12] FIG. 11 is an explanatory diagram showing an example of a blowing direction of a second hot air stream. [Figure 13] FIG. 11 is an explanatory diagram showing another example of the blowing direction of the second hot air. [Figure 14] FIG. 11 is an explanatory diagram showing an air blowing process. 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 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 together 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, a skin-facing side 10T and a non-skin-facing side 10B, with the first fiber layer M1 arranged on the skin-facing side 10T and the second fiber layer M2 arranged on the non-skin-facing side 10B. The skin-facing side 10T refers to the side that faces the skin of a wearer when the nonwoven fabric 10 is incorporated into an absorbent article, and the non-skin-facing side 10B refers to the side opposite to the side that faces the skin of a wearer. The first fiber layer M1 is also referred to as the upper layer, and the second fiber layer M2 is also referred to as the lower layer. The skin-facing side 10T and the non-skin-facing 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 recesses 1 with spaces 1A that open toward the skin side 10T, and openings 3 that penetrate in the thickness direction between adjacent recesses 1, 1. The penetration of the openings 3 here means that, focusing on the first fiber layer M1, the portions of the first fiber layer M1 where no constituent fibers are arranged penetrate both sides of the first fiber layer M1 in the thickness direction Z.

[0013] The space 1A is a space that is not substantially filled with the fibers of the nonwoven fabric 10. Specifically, the space 1A is a space that is not substantially filled with the fibers of the nonwoven fabric 10 when the fiber density determined by the method described later is 10 fibers / mm 2 This means that the fiber density in the space 1A is less than 100%. The smaller the fiber density in the space 1A, the better.

[0014] (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, the opening 3 between the recesses 1, 1). 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 2This 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.

[0015] 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 area between adjacent recesses 1, 1 is shown as the openings 3, but the size of the openings 3 can be selected appropriately. For example, the openings 3 may penetrate in the thickness direction while including the fiber layers extending from the recesses 1 of the first fiber layer M1 toward 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 openings 3 can be measured using the above-mentioned microscope. Specifically, the nonwoven fabric 10 is viewed in plan from the skin-facing side 10T, the areas of the openings 3 are measured at 10 points using the microscope, and the average value is taken as the opening area of ​​each opening.

[0016] The area of ​​the opening 3 is set to 1.0 mm2 in order to enhance the permeability of the liquid in the soft stool. 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:

[0017] The planar shape of the openings 3 may be various from the viewpoint of increasing the permeability of the liquid in loose stool, and examples of such shapes include a circle, an ellipse, and a rectangle.

[0018] In the first fiber layer 1, each of the multiple recesses 1 has a wall 1B extending perpendicular to the planar direction of the nonwoven fabric 10. The planar direction of the nonwoven fabric 10 means the direction along the plane of the non-skin facing side 10B of the second fiber layer M2. Furthermore, each of the recesses 1 has a bottom 1C on the non-skin facing side 10B. As a result, in each of the recesses 1, the aforementioned space 1A is partitioned by the fiber layer of the wall 1B and the fiber layer of the bottom 1C to form an area that opens toward the skin facing side 10T. The bottom 1C of the recess 1 is a fiber layer located on the non-skin facing side 10B of the first fiber layer 1, and refers to an area that includes an end (also called a base 1D) of the non-skin facing side 10B of the wall 1B, adjacent bases 1D, and a connection 1U between the bases 1D.

[0019] When the nonwoven fabric 10 is used as a top sheet of an absorbent article, the space 1A of the recess 1 on the skin-facing side 10T and the opening 3 between the recesses 1, 1 are difficult to contact with the skin. That is, the skin contact area on the skin-facing side 10T of the nonwoven fabric 10 is reduced due to the presence of multiple walls 1B, and the non-contact area between the wearer and the nonwoven fabric 10 is increased. This can improve the breathability of an absorbent article incorporating the nonwoven fabric 10 as a top sheet, and can improve the dryness of the wearer's skin surface. In addition, the return path of loose stool from the nonwoven fabric 10, which becomes the top sheet, to the wearer's skin surface can be reduced, suppressing the opportunity for the liquid contained in the loose stool to reattach to the skin surface, thereby further improving the above-mentioned dryness. Furthermore, as mentioned above, the wall portion 1B of the first fiber layer M1 is vertically connected to the second fiber layer M2 on the non-skin side 10B, making it less likely to wear out, and the space portion 1A and the opening portion 3 are less likely to collapse, making it easier to maintain the dryness mentioned above.

[0020] The "perpendicular" of the wall 1B means that the angle θ with respect to the plane of the non-skin facing 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 non-skin facing side 10B of the nonwoven fabric 10 and an extension line of the wall 1B. Specifically, as shown in FIG. 1, in a cross section in the thickness direction including the recess 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 a straight line L tangent to the surface of the non-skin facing 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.

[0021] 1, the wall 1B extends linearly in the thickness direction, 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 curved or wavy extending portion. In this case, the angle θ is specified by taking the perpendicular line from 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 non-skin-facing side 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 recesses 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.

[0022] In the first fiber layer 1, the bottom portion 1C including the root portion 1D of the wall portion 1B abuts against the second fiber layer M2. In the abutment region 4 between the root portion 1D and the second fiber layer M2, the root portion 1D is embedded in and integrated (fixed) with the second fiber layer M2. From the viewpoint of increasing the bonding strength and maintaining the uneven shape of the first fiber layer M1, it is preferable that the root portion 1D of the wall portion 1B and the second fiber layer M2 are integrated by a 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. Furthermore, it is preferable that the entire bottom portion 1C including the root portion 1D is embedded in the second fiber layer M2 and integrated by the fused fiber portion.

[0023] In the cross section in the thickness direction Z of the nonwoven fabric 10 including the recesses 1 of the first fiber layer M1 and the second fiber layer M2, the fiber layers 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 recesses 1 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 (non-skin-facing side 10B) facing down. Next, a flat plate (e.g., a flat acrylic plate) is placed on the skin-facing side 10T of the nonwoven fabric 10, and a pressure of 4.9 mN / cm is applied. 2 In this state, the cross section in the thickness direction Z is observed under the microscope at 20 times, and the portion connecting the portion of the first fiber layer M1 in contact with the flat plate and the surface of the skin side 10T of the second fiber layer M2 is determined to be the wall portion 1B.

[0024] The second fiber layer M2 is disposed on the non-skin side 10B of the first fiber layer M1, and has a protuberance 5 on the side facing the first fiber layer M1, which protrudes from the opening 3 of the first fiber layer M1 into the region defined by the wall 1B. That is, the protuberance 5 is located in the space of the opening 3, which is closer to the skin side 10T than the base 1D of the wall 1B. Meanwhile, the second fiber layer M2 in the contact region 4 adjacent to the protuberance 5 is formed into a recess 6 by being bitten into by the wall 1B (see FIG. 2). As described above, it is preferable that the entire bottom 1C including the base 1D is bitten into the second fiber layer M2, and the second fiber layer M2 abutting the entire bottom 1C is formed into the recess 6.

[0025] 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 (skin-facing side 10T), the recess 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 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 recess 1 and the skirt portion 7 (see FIG. 2) of the raised portion 5 extending to the base portion 1D. In addition, since the wall portion 1B has a vertical wall surface, the valley between the raised portion 5 at the base portion 1D of the wall portion 1B becomes narrower, and the shadow becomes stronger. In addition, the shadow can be recognized as being raised from the vertical wall portion 1B. This further improves the visibility of the opening 3.

[0026] In the nonwoven fabric 10, the above-mentioned emphasis of shading improves the visibility of the openings 3 when viewed from the first fiber layer M1 side (the skin-facing 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.

[0027] This visibility allows the user to visually clearly understand that the absorbent article incorporating the nonwoven fabric 10 as a topsheet has clear openings in the topsheet. As a result, the user can be reminded of the permeability of loose stool through the openings 3 in the topsheet, i.e., the high absorbency of loose stool in the absorbent article, providing the user with an opportunity to use the absorbent article with peace of mind. In fact, the presence of the raised portions 5 of the second fiber layer M2 penetrating into the first fiber layer M1 in the nonwoven fabric 10 facilitates the transfer of loose feces from the first fiber layer M1 to the second fiber layer M2 through the openings 3. This, combined with the reduction in the skin contact area described above, makes it possible for the soft feces to be more easily permeable to the top sheet of an absorbent article incorporating the nonwoven fabric 10 as a top sheet, and further reduces the area through which soft feces spreads, making it less likely for soft feces to remain on the skin.

[0028] In nonwoven fabric 10, the fibers of wall 1B are preferably oriented in the thickness direction relative to the plane of non-skin facing side 10B of nonwoven fabric 10. In this specification, orientation in the thickness direction relative to the plane of nonwoven fabric 10 is sometimes referred to as longitudinal orientation. The raised portion 5 has a fiber orientation different from that of the wall portion 1B, and a dividing line is formed where the fiber orientation degree changes discontinuously between the two portions, further emphasizing the above-mentioned shading. In the example shown in Fig. 1, the space between the adjacent recesses 1, 1 is an opening 3, and the bottom 7 of the raised portion 5 is shown as directly connected to the base 1D of the wall portion 1B. In addition, the longitudinal orientation of the fibers enhances the support force of the wall portion 1B against the second fiber layer M2 in the thickness direction, and makes it easier to maintain the thickness of the recess 1 of the nonwoven fabric 10 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 maintain 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 top sheet in an absorbent article, the liquid permeation effect of loose stool is more likely to be sustained even under load, and the return of liquid contained in loose stool from the absorbent to the skin side is suppressed. The three-dimensional shape of the wall portion 1B acting in this way can be well maintained by being integrated with the second fiber layer M2 with high strength by the above-mentioned fiber fusion part. In addition, since this integration utilizes the bonding state by the fiber fusion part at the intersection of the fibers, it is not necessary to collapse the lower part of the wall portion 1B to ensure an adhesive surface as in the case of bonding with a conventional adhesive such as a hot melt type adhesive. This allows the height of the wall portion 1B to be maintained at a sufficient level.

[0029] 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.

[0030] (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 recess 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 the straight line L tangent to the surface of the non-skin facing side 10B of the second fiber layer M2 shown in Figure 1. The thickness direction corresponds to the direction Z perpendicular to the straight line L.

[0031] In the nonwoven fabric 10, the fibers of the second fiber layer M2 are preferably oriented in the planar direction of the nonwoven fabric. In this specification, the orientation in the planar direction of the nonwoven fabric 10 may also be referred to as transverse orientation. The orientation in the planar direction (transverse orientation) means that there are many fibers aligned along the planar direction of the nonwoven fabric 10. Specifically, it means that the longitudinal orientation ratio ((number of longitudinal fibers) / (number of transverse fibers+number of longitudinal fibers)×100(%)) obtained by applying the above-mentioned (Method of measuring the longitudinal orientation ratio of fibers in the wall portion 1B) is 45% or less. This makes the second fiber layer M2 have a fiber orientation different from that of the wall portion 1B, and the above-mentioned shadow is further emphasized. From the viewpoint of further enhancing this effect, the longitudinal orientation ratio of the fibers of the second fiber layer M2 is more preferably 38% or less, and even more preferably 37% or less. The longitudinal orientation ratio of the fibers in the second fiber layer M2 is preferably 20% or more, and more preferably 30% or more, from the viewpoint of maintaining the shape and strength of the nonwoven fabric. In measuring the transverse orientation ratio by applying the above-mentioned (method of measuring the longitudinal orientation ratio of fibers in the wall portion 1B), the measurement is performed on the raised portion 5 of the second fiber layer M2 as shown in FIG. 1 according to the following procedure. That is, a fiber layer cross section including the protrusions 1 of the first fiber layer M1 and the protuberances 5 defined in the cross section of the thickness direction of the nonwoven fabric 10, including the protrusions 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 drawn on the observed image as a reference line. At this time, the line is drawn so that the fibers of the protuberances 5 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 lines 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.

[0032] From a similar viewpoint, it is preferable that the bottom 7 extending downward from the rising 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, the valley between the base portion 1D of the wall portion 1B and the bottom 7 becomes clearer, and the shadow around the opening 3 between the adjacent recesses 1, 1 of the first fiber layer M1 is more emphasized.

[0033] From the viewpoint of making the above-mentioned emphasis of the 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 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 skirt 7 refer to the fibers in the portion that starts to rise from the base 1D of the wall 1B in the contact region 4. For example, the fibers are the surface fibers in a region that is within a range of 2 mm in the planar direction from the base 1D toward the skirt 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.

[0034] (Method of measuring the longitudinal orientation rate of fibers on the surface of the hem portion 7) A cross section of the fiber layer including the recesses 1 and the openings 3 of the first fiber layer M1 and the skirt 7 defined in the cross section of the thickness direction of the nonwoven fabric 10, including the recesses 1 and the openings 3 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 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 of the cross section of the nonwoven fabric 10. The total number of fibers passing through the reference lines 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.

[0035] 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 the permeability of soft stool 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 the skin-facing side 10T of the wall portion 1B 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.

[0036] 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 25 g / m is preferable. 2 More preferably, 30 g / m 2 The weight of the nonwoven fabric 10 is preferably 100 g / m2 or more so as not to impede the comfortable feel of the wearer.2 Less than 90 g / m 2 Less than 85 g / m is more preferable. 2 The following is even more preferred:

[0037] (Method of measuring basis weight of nonwoven fabric 10) The area and mass of the nonwoven fabric 10 stored for 24 hours or more in an environment of 23±2° C. and a relative humidity of 50±5% are measured to determine the elasticity.

[0038] 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. 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 ability to prevent the return of liquid contained in loose stool 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.

[0039] (Method of measuring thickness of nonwoven fabric 10) 4.9mN / cm for nonwoven fabric 10 2 (0.05gf / cm 2 The thickness is measured with a thickness measuring device under a load of 100 mm. A laser displacement meter manufactured by Omron Corporation is used as the thickness measuring device. Measurements are taken at 10 points, and the average value is calculated to determine the thickness.

[0040] Next, a specific example (nonwoven fabric 20) of the nonwoven fabric 10 shown in Fig. 1 will be described with reference to Fig. 3 to Fig. 7. The nonwoven fabric 20 has the configuration described above for the nonwoven fabric 10. The nonwoven fabric 20 shown in Figures 3 to 7, when viewed in a plan view from the skin-facing side 20T, has a plurality of vertical groove portions 11 as the recesses 1 of the first fiber layer M1 described above, which extend in one direction Y and are arranged at a distance from each other in a direction X intersecting the one direction Y. The one direction Y and the direction X intersecting the one direction Y can be appropriately set according to the purpose on the skin-facing 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 of an absorbent article such as a topsheet, 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.

[0041] Each of the vertical grooves 11 has a space 11A that opens toward the skin-facing side 20T, and a wall 11B that protrudes perpendicular to the planar direction of the nonwoven fabric 20 and extends along one direction Y (FIGS. 3 to 7). Each of the vertical grooves 11 further has a bottom 11C that extends in one direction X on the non-skin-facing side 10B. Bottom 11C has a base 11D of wall 11B and a connecting portion 11U. The "vertical" of wall 11B means 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 non-skin facing side 20B of nonwoven fabric 20 (second fiber layer M2) in a cross section perpendicular to the extension direction of vertical groove 11 (thickness direction cross section at line R1-R1 along direction X intersecting direction Y in FIG. 3), as shown in Fig. 4. This angle θ can be determined by observing a micrograph of the cross section along line R1-R1 obtained with the above-mentioned microscope. As described above, the fibers in the wall portion 11B are preferably oriented vertically. 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 longitudinal groove portion 11 (a thickness direction cross section at the position of line R1-R1 along the width direction X in FIG. 3), as shown in FIG. 4.

[0042] The nonwoven fabric 20 has the vertical grooves 11 and horizontal grooves 15 connecting adjacent vertical grooves 11, 11 as the recesses 1 in the first fiber layer M1. The horizontal grooves 15, like the vertical grooves 11, have spaces 15A that open toward the skin-facing side 20T and walls 15B that protrude perpendicularly to the planar direction of the nonwoven fabric 20 and extend along a direction X intersecting with the direction Y (FIGS. 3 and 6). Each of the vertical grooves 11 further has a bottom 15C that extends in the direction X intersecting with the direction Y on the non-skin-facing side 20B. The bottom 15C has a root 15D of the wall 15B and a connecting portion 15U. The "vertical" is synonymous with the "vertical" defined in the vertical grooves 11. It is preferable that the fibers of the wall 15B are vertically oriented as described above. The longitudinal orientation rate indicating the longitudinal orientation of wall portion 15B in lateral groove portion 15 and the "vertical" of wall portion 15B can be measured in a cross section perpendicular to the extension direction of lateral groove portion 15 (thickness direction cross section at the position of line R3-R3 along one direction Y in FIG. 3) as shown in FIG. 6, in the same manner as the measurement method described above for wall portion 11B.

[0043] From the viewpoint of texture, it is preferable that the walls 11B of the vertical grooves 11 and the walls 15B of the horizontal grooves 15 have the same height. 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.

[0044] The lateral grooves 15 are arranged in a plurality of band regions 16 extending parallel to the longitudinal grooves 11 between the longitudinal grooves 11, 11 in a plan view of the skin-facing side 20T of the nonwoven fabric 20. In each band region 16, a plurality of lateral grooves 15 are arranged at intervals along the extension direction Y of the parallel longitudinal grooves 11. The aforementioned openings 3 are located at the intervals between the lateral grooves 15. That is, in each band region 16, the lateral grooves 15 and the openings 3 are alternately arranged. As a result, the openings 3 are surrounded and partitioned by the walls 11B of the longitudinal grooves 11 and the walls 15B of the lateral grooves 15. More specifically, the box-shaped or cylindrical openings 3 are arranged in an area surrounded by the walls 11B and 15B, which are three-dimensional fiber layers erected in the thickness direction.

[0045] In the nonwoven fabric 20, the raised portions 5 of the second fiber layer M2 extend from the openings 3 into the regions defined by the walls 11B and 15B. The raised portions 5 of the second fiber layer M2 are surrounded by the walls 11B and 15B in a box-like or cylindrical shape, which is preferable because it emphasizes the shadows around the openings 3. That is, the walls 11B and 15B on all four sides surrounding the raised portions 5 have contact regions 4 with the second fiber layer M2, and valleys between the base portions 11D and 15D of the walls 11B and 15B and the hem portions 7 of the raised portions 5, and shadows caused by these valleys are formed on all four sides, so that the contours of the raised portions 5 and the openings 3 can be more clearly seen.

[0046] In the example shown in Figs. 3 to 7, in plan view from the skin-facing side 20T of the nonwoven fabric 20, adjacent band regions 16, 16 with vertical grooves 11 between them are arranged in a staggered manner such that the positions between the openings 3, 3 of one band region 16 correspond to the openings 3 of the other band region 16. As a result, the openings 3 in the band regions 16 adjacent to each other with vertical grooves 11 between them are not aligned at the ends in one direction Y, but are arranged offset in the one direction Y. This staggered arrangement extends over the entire planar direction of the nonwoven fabric 20. The staggered openings 3 are arranged like islands that exist independently in the fiber layers of the vertical grooves 11 and the horizontal grooves 15 that intersect and connect vertically and horizontally (Figs. 3, 5 and 7).

[0047] In the nonwoven fabric 20, the arrangement of the vertical grooves 11 and the horizontal grooves 15 is not limited to the staggered arrangement described above, and various arrangements are possible. For example, the positions of the ends of the openings 3 in the one direction Y of the adjacent band-shaped regions 16 separated by the vertical grooves 11 may be aligned. In this case, the vertical grooves 11 and the vertical grooves 15 are arranged in a lattice pattern, and the openings 3 are dotted in the lattice to form a square pattern.

[0048] Next, a preferred embodiment of a method for producing the nonwoven fabric 20 will be described with reference to Figures 8 to 14. The production method described below can also be applied to the production method for the nonwoven fabric 10. As shown in FIG. 8, the manufacturing method of this embodiment includes the following four steps (hereinafter, each step may be referred to as step (I), step (II), step (III), and step (IV)). (I) A pressing process in which the 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 the pressing portion 131 of the pressing member 130 to form a shape, and holes are opened at locations of the first fiber web 100 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 130 from the support 120, and then blowing a first hot air W1 onto the porous fibrous web 101 to fuse the fibers together to obtain the porous nonwoven fabric 102. (III) A step of supplying the second fibrous web 103 and laminating the second fibrous web 103 onto the surface of the porous nonwoven fabric 102 that has been pressed into the recesses 125 of the support 120 . (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.

[0049] 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.

[0050] In step (I), as shown in FIG. 8(A), the first fiber web 100 on the support 120 is directly pressed with mechanical pressure using a pressing member 130. This forms an uneven perforated fiber web 101 that will become the first fiber layer M1 in the nonwoven fabric 20. This type of shaping results in stronger fiber orientation and a perpendicular orientation to the nonwoven fabric plane compared to pressing with non-mechanical pressure such as wind. Furthermore, it is not necessary to apply a large pressing force to increase the unevenness height difference formed on the first fiber web 100, and the first fiber web 100 can be shaped softly. Furthermore, fiber disorder can be suppressed to improve shaping properties.

[0051] The support 120 is drum-shaped as shown in Fig. 8, for example, and has protrusions 121 as shown in Fig. 8(A) on the drum peripheral surface. On the drum peripheral surface of the support 120, a plurality of protrusions 121 are arranged at intervals in one direction (first direction D1) and a direction perpendicular thereto (second direction D2), as shown in Fig. 9, for example. A plurality of protrusion rows 121A, each of which is formed by arranging a plurality of protrusions 121 in the first direction D1, are arranged at a distance from each other in the second direction D2. The protrusions 121 have peaks 122 at their tips. The peaks 122 form the openings 3 in the bottom portion 12 of the first fiber layer M1. The planar shape of the projection 121 as viewed from the spire 122 side is not limited to a rectangle as shown in Fig. 9, but may be various shapes, such as a circle, an ellipse, or a diamond. The recess 125 has a first recess 125A extending in the first direction D1 between the protrusion rows 121A, 121A, and a second recess 125C located between the protrusions 121, 121 in the protrusion row 121A. The second recess 125C is connected to the adjacent first recess 125A, and extends intermittently in the second direction D2 via the first recess 125A.

[0052] In the support 120, a plurality of protrusions 121 are arranged corresponding to positions where the apertures 3 of the first fiber layer M1 of the nonwoven fabric 20 are to be formed. The second recesses 125C between the protrusions 121, 121 in the protrusion row 121A are located at positions where the lateral grooves 15 of the first fiber layer M1 of the nonwoven fabric 20 are to be formed. In other words, the protrusion row 121A is located at a position that becomes the band regions 16 between the longitudinal grooves 11, 11 of the first fiber layer M1 of the nonwoven fabric 20. The first recesses 125A are located at a position that becomes the longitudinal grooves 11 of 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).

[0053] The pushing member 130 is in the form of a roll as shown in Fig. 8, for example, and has a pushing portion 131 as shown in Fig. 8(A) on the roll peripheral surface. On the roll peripheral surface of the pushing member 130, a plurality of pushing portions 131 continuing in the first direction D1 are arranged at intervals in the second direction D2 as shown in Fig. 10, for example. Between the pushing portions 131, 131, a recess 132 continuing in the first direction D1 is formed. The pushing portion 131 of the pushing member 130 corresponds to the first recess 125A of the support body 120. The recess 132 of the pushing member 130 corresponds to the protrusion row 121A of the support body 120. The bottom of the recess 132 of the pushing member 130 has a structure that allows hot air to pass through, and for example, a plurality of holes (not shown) are provided therein.

[0054] The height of the pushing portion 131 of the pushing member 130 is preferably 1 mm or more so that it can be sufficiently inserted between the protrusions 121 of the support 120 .

[0055] 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.

[0056] In step (I), the protrusions 121 of the support 120 are inserted into the recesses 132 of the pushing member 130. The pushing portions 131 of the pushing member 130 are inserted into the first recesses 125A of the support 120 (FIGS. 8(A) and 11). This pushing between the support 120 (FIG. 9) and the pushing member 130 (FIG. 10) can favorably form the uneven shape of the first fiber layer M1. The first fiber web 100 is pressed and shaped by the pressing part 131 of the pressing member 130 at the position of the first recess 125A of the support 120. This part becomes the vertical groove part 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 part 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 part becomes the wall part 11B of the vertical groove part 11 in the first fiber layer M1 of the nonwoven fabric 20. In addition, the part of the shaped fibers pressed into the first recess 125A of the support 120 by the pressing part 131 becomes the bottom part 11C of the vertical groove part 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 bottoms of the recesses 132 of the pushing member 130 and opened. These portions become the open portions 3 in 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 lateral groove portion 15 in the first fiber layer M1 of the nonwoven fabric 20. The lateral groove portion 15 has a wall portion 15B, and the wall portion 15B is similar to the wall portion 11B of the vertical groove portion 11. Furthermore, the portion of the shaped fiber that has been pushed into the second recess 125C of the support 120 by the pushing portion 131 becomes the bottom portion 15C of the lateral groove portion 11 in the first fiber layer M1 of the nonwoven fabric 20.

[0057] 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.

[0058] Next, in step (II), after removing the pushing member 130 from the support 120, a first hot air W1 is blown onto the porous fiber web 101 to fuse the fibers together to obtain a porous nonwoven fabric 102 (FIG. 8(B)). This porous nonwoven fabric 102 becomes the first fiber layer M1 of the nonwoven fabric 20. For example, the porous fiber web 101 is rotated while being held on the support 120, and passes through the meshing portion between the support 120 and the pushing member 130, and the pushing member 130 inserted into the support 120 is removed when the meshing is released. The support 120 further rotates, and the first hot air W1 is blown onto the porous fiber web 101 at the position of the hot air blowing section 140. The support 120 preferably has a hot air suction section 141 at a position facing the hot air blowing section 140 inside the drum.

[0059] 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.

[0060] Next, in step (III), the second fiber web 103 is supplied and laminated on the surface of the porous nonwoven fabric 102 that has been pushed into the recesses 125 of the support 120 (FIG. 8(C)). More specifically, the second fiber web 103 is supplied to the surface of the fibers that have been pushed into the recesses 125 (first recess 125A and second recess 125C) of the support 120 by the pushing section 131, i.e., the surface of the bottoms 11C and 15C of the first fiber layer M1 of the nonwoven fabric 20. For example, the porous nonwoven fabric 102 formed by blowing the first hot air W1 is separated from the drum surface of the support 120, and the side on which the bottoms 11C and 15C are formed by the pushing section 131 is placed downward, and the second fiber web 103 is joined to the side of the bottoms 11C and 15C while being transported downstream on a belt conveyor.

[0061] Next, in step (IV), a second hot air W2 is blown in a fusion furnace 170 to fuse the fibers of the porous nonwoven fabric 102 and the second fibrous web 103 together and fuse the fibers in the second fibrous web 103 together (FIG. 8(D)). This integrates the porous nonwoven fabric 102 and the second fibrous web 103 and also turns the second fibrous web 103 into a nonwoven fabric. This nonwoven fabric of the second fibrous web 103 becomes the second fiber layer M2 of the nonwoven fabric 20. At this time, the second hot air W2 may be blown from the side of the porous nonwoven fabric 102 as shown in Fig. 8(D) and Fig. 12, or from the side of the second fibrous web 103 as shown in Fig. 13. In either case, by blowing the second hot air W2, the porous nonwoven fabric 102 and the second fibrous web 103 come into close contact with each other, and the fibers of the second fibrous web 103 move. As a result, the fibers of the second fibrous web 103 enter the area partitioned by the walls 11C and 15C from the apertures 3 of the porous nonwoven fabric 102, and the protrusions 5 are formed. At the same time, the walls 11B and 15B bite into the second fibrous web 103. This biting is caused by the second hot air W2, so that the shapes (heights) of the walls 11B and 15B are easily maintained, and in this maintained state, the walls 11B and 15B are tightly adhered and integrated with the second fiber web 103. In this manner, the unevenly porous nonwoven fabric 102 (first fiber layer M1) and the second fiber layer M2 (the nonwoven product of the second fiber web 103) are tightly adhered and integrated with each other, and the nonwoven fabric 20 described above is obtained. Regarding the formation of the above-mentioned raised portions 5, it is preferable to blow the second hot air W2 from the side of the second fiber web 103 as shown in FIG. 13, since this causes the fibers to move more strongly from the side of the second fiber web 103, and the raised portions 5 are formed more clearly.

[0062] 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.

[0063] As described above, the nonwoven fabric of the present invention can be suitably produced by the method for producing a nonwoven fabric of the present embodiment, which includes the above-mentioned steps (I), (II), (III) and (IV).

[0064] In the above manufacturing method, the push-in member 130 is not limited to one having push-in portions 131 that are continuous in the first direction D1 as shown in Fig. 10. For example, the push-in portions 131 may be formed in a lattice shape, and square-shaped recesses 132 may be formed between the lattice-shaped push-in portions 131.

[0065] In the manufacturing method of the nonwoven fabric of this embodiment, before blowing the first hot air W1 in step (II), a step of blowing air WF may be performed as shown in Fig. 14. More specifically, the pushing member 130 is removed from the support 120, and air WF is blown onto the porous fibrous web 101 placed on the support 120 from the side of the spires 122 of the protrusions 121 of the support 120. The temperature of the air WF is set to be equal to or lower than the melting point of the constituent fibers of the porous fibrous web 101. This blowing pushes the fibers remaining on the protrusions 121 along the wall surfaces of the protrusions 12 and straightens out any disorder in the fibers. This suppresses fuzzing of the walls 11B and 15B in the first fiber layer M1 of the nonwoven fabric 20 and further uniforms the height. The air WF can be sprayed by a commonly used means, for example, an air duster gun. In order to more effectively perform the above-mentioned shaping, it is preferable that the air WF be blown from directly above the porous fibrous web 101 shaped along the support 120 .

[0066] In the manufacturing method of the nonwoven fabric of this embodiment, it is preferable to have a cooling step after blowing the first hot air W1. For example, as shown in FIG. 8, it is preferable to arrange a cooling section 160 having a cooling nozzle and a cooling suction section 161 inside the drum of the support 120 opposite each other at a position where the porous nonwoven fabric 102 obtained by blowing the first hot air W1 is aligned along the outer periphery of the drum of the support 120. This makes it possible to keep the support 120 at a certain temperature or lower, and to peel off the obtained nonwoven fabric while maintaining its shape. As a result, in the manufactured nonwoven fabric 20, the shapes of the walls 11B and 15B of the first fiber layer M1 are well maintained, and good cushioning properties and better visibility of the open holes 3 can be achieved.

[0067] 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.

[0068] The nonwoven fabric for absorbent articles of the present invention can be used as a component of various absorbent articles, which 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.

[0069] An absorbent article having the nonwoven fabric for absorbent articles 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 for absorbent articles of the present invention can be suitably used as the top sheet that comes into contact with the skin of the wearer. EXAMPLES

[0070] 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 there is no value corresponding to the item.

[0071] [Example 1] The nonwoven fabric shown in FIGS. 3 to 7 was produced by carrying out the steps described below 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 1.8 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 3.0 m / sec. The unevenly perforated nonwoven fabric 102 produced had an area of ​​the open hole 3 of 6.12 mm 2 , basis weight 30g / m 2 It was. Next, a second fiber web 103 made of thermoplastic fibers having a core-sheath type (polyethylene terephthalate (PET) / polyethylene (PE)=5:5) with a fineness of 7.8 dtex was laminated on the surface side of the unevenly porous nonwoven fabric 102 pressed into the recesses 125 of the support 120, and a second hot air W2 was blown on the surface side to perform a fusion treatment, thereby producing 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 1.5 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 extended perpendicularly to the planar direction of the nonwoven fabric sample. The second fiber layer M2 had a protrusion 5 extending from the opening 3 into the region defined by the walls 11B and 15B.

[0072] [Comparative Example 1] A nonwoven fabric sample of Comparative Example 1 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).

[0073] [Comparative Example 2] 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 2. The nonwoven fabric sample of Comparative Example 2 did not have any openings 3 in the first fiber layer M1.

[0074] [Comparative Example 3] A laminated nonwoven fabric was produced in the same manner as in Example 1, except that instead of laminating the second web 103 on the porous nonwoven fabric 102, the second web 103 was made into a second nonwoven fabric by a fusion process, and then the second nonwoven fabric was laminated on the porous nonwoven fabric to form a laminated nonwoven fabric. This laminated nonwoven fabric was used as the nonwoven fabric sample for Comparative Example 3. The nonwoven fabric sample of Comparative Example 3 did not have a bottom hem 7 or a protruding portion 5 .

[0075] The nonwoven fabric samples of Example 1 and Comparative Examples 1 to 3 were measured for the skin contact area ratio, the visibility of the open holes, the absorption time of loose stool, and the diffusion area of ​​loose stool. The measurement methods are shown below. In addition, the fiber density of the space, the thickness of the nonwoven fabric, the longitudinal orientation rate of the wall, the bottom, and the raised parts, the angle of the wall, the thickness ratio (raised part thickness H2 / first fiber layer thickness H1), and the area of ​​the open holes were measured according to the above-mentioned respective measurement methods. The measurement results are shown in Table 1.

[0076] <Skin contact area ratio> (1) Cut a measurement sample measuring 50 mm x 50 mm from the nonwoven fabric. (2) The measurement sample is placed with the measurement surface (the surface on which the first fiber layer M1 is disposed) facing up. (3) Using a high-precision shape measurement system KS-1100 (product name, manufactured by Keyence Corporation), the measurement surface is irradiated with laser light to measure the surface shape (the height and depth of the thickness that rises and falls along the surface direction of the measurement surface) of the measurement surface in a no-load state (natural state without load) and an image is captured. 2 (Measurement pitch: 20 μm vertically, 20 μm horizontally), and the movement speed is 10 cm / sec. (4) Next, a transparent acrylic plate with a mass of 170 g is placed on the measurement surface of the measurement sample, and a weight with a mass of 600 g is further placed on the acrylic plate. Under this condition, a pressure of 3 kPa is applied, and the surface shape of the measurement surface is measured and an image is captured in the same manner as in (3) above. (5) The images captured in (3) and (4) above are analyzed using a shape analysis application called KS-Analyzer (product name, manufactured by Keyence Corporation). Specifically, the area where the thickness changes from the no-load state to the application of a pressure of 3 kPa (minimum measurable scale: 0.01 μm) is extracted and binarized to obtain a surface image of that area. (6) The surface image of the part where the thickness has changed obtained in (3) above is imported and processed using image processing software NewQube (Ver. 4.22, product name, manufactured by Nexus Co., Ltd.), and its area is measured. This area corresponds to the area of ​​the part that comes into contact with the skin when the nonwoven fabric of the measurement sample is pressurized with 3 kPa, i.e., the skin contact area. (7) The measured skin contact area is divided by the area of ​​the measurement sample (measurement points: 251,001 points (= 501 x 501)) to calculate the "skin contact area ratio (%)" of the measurement surface of the nonwoven fabric to be measured.

[0077] <Visibility of openings> A commercially available baby diaper (product name "Merry's Smooth Air Through S Size", Kao Corporation, manufactured in 2020) was used with the top sheet removed to form 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 values ​​were compiled. The diaper for evaluation was left stationary, and the nonwoven fabric was visually observed from above to perform the sensory evaluation.

[0078] (Sensory evaluation criteria) 5: It appears as though clear openings have been formed throughout the entire surface sheet. 4: The impression is that there is a mixture of clear and unclear openings across the entire surface sheet. 3: The impression is that unclear openings have been formed throughout the entire top sheet. 2: Only some of the surface sheets have unclear openings, and most of the surface sheets have no openings. 1: It seems as though there are no holes at all in the surface sheet.

[0079] <Absorption time of soft stool> Diapers for evaluation were prepared in the same manner as in the above <Visibility of Openings>. Each of the diaper samples described above was unfolded flat, and 10 g of simulated loose stool was poured into each diaper sample at a flow rate of 6 g / s at a position 30 mm behind the center in the longitudinal direction. The time it took for the simulated loose stool to be completely absorbed (the time it took for the stool to penetrate through the surface of the diaper and expose the surface material) was measured and used as the loose stool absorption rate. The measurement was performed three times, and the average value was used as the loose stool absorption rate. The faster the absorption rate, the easier it is for the liquid contained in the loose stool to penetrate into the inside, indicating excellent liquid absorbency. The artificial soft stool was prepared by mixing 20% ​​bentonite (Kanto Chemical Co., Ltd., product number: 04066-01, standard: Grade 1 deer), 0.5% Poise 530 (Kao Corporation), 1.5% Emulgen 130K (Kao Corporation), and 78% ion-exchanged water using a digital mixer until the viscosity reached 40 cP (tuning fork vibration viscometer: A&D Co., Ltd., SV-10).

[0080] <Spread area of ​​soft stool> Diapers for evaluation were prepared in the same manner as in the above <Visibility of Openings>. The diaper was spread out flat, and 10 g of simulated soft stool (viscosity 40 mPa s) was poured into the diaper at a position 30 mm behind the longitudinal center at a flow rate of 6 g / s. The simulated soft stool was made by dispersing bentonite in ion-exchanged water, and the bentonite concentration was adjusted to a viscosity of 40 mPa s. The simulated soft stool was prepared in the same manner as in the above <Absorption time of soft stool>. Next, a resin film (100 mm x 100 m, mass measurement W1) was placed on the injection position, and a weight was placed on the resin film to apply a pressure of 3 kPa, and the film was left to stand for 2 minutes. After the film was left to stand, the area of ​​the artificial feces spread on the resin film was transferred to an OHP sheet, scanned, and imported into Image-Pro to determine the area of ​​the soft feces spread. The measurement was performed three times, and the average value was taken as the area of ​​the soft feces spread. The amount of feces returned was calculated using the following formula. Amount of return (g) = Mass of resin film after pressure (W2) - Initial mass of resin film (W1)

[0081] [Table 1]

[0082] As shown in Table 1, the nonwoven fabric sample of Example 1 had a higher evaluation score for "visibility of openings" than the nonwoven fabric samples of Comparative Examples 1 to 3, and was more likely to remind users of the soft stool absorption ability of the openings. In addition, the nonwoven fabric sample of Example 1 had a shorter "absorption time of loose stool" and a smaller "diffusion area of ​​loose stool" than the nonwoven fabric samples of Comparative Examples 1 to 3, and therefore had improved soft stool absorbency. From the above, it was found that the nonwoven fabric sample of Example 1 was more likely to impress upon the user a high level of soft stool absorbency than the nonwoven fabric samples of Comparative Examples 1 to 3, and was therefore superior in actual soft stool absorbency. [Explanation of symbols]

[0083] M1 First fiber layer M2 2nd fiber layer 1 Recess 1A space section 1B Wall section 1C bottom 3 Opening part 5 Protuberance 10, 20 Nonwoven fabric 10T, 20T Skin side 10B, 20B Non-skin side

Claims

1. A nonwoven fabric having a first fiber layer and a second fiber layer laminated in the thickness direction, and including fiber fusion portions at the intersections of the fibers, The first fiber layer has a plurality of recesses with spaces that open toward the skin side, and openings that penetrate in the thickness direction between adjacent recesses. Each of the aforementioned plurality of recesses comprises a wall portion extending perpendicular to the planar direction of the nonwoven fabric and a bottom portion. The second fiber layer is disposed on the non-skin side of the first fiber layer and has a raised portion on the side facing the first fiber layer that enters the region partitioned by the wall portion from the opening portion of the first fiber layer, wherein it is a nonwoven fabric for absorbent articles.

2. The raised portion is visible from the side of the first fiber layer, as described in claim 1, for an absorbent nonwoven fabric for articles.

3. The nonwoven fabric for absorbent articles according to claim 1 or 2, wherein the fibers of the second fiber layer are oriented in the planar direction of the nonwoven fabric.

4. The nonwoven fabric for absorbent articles according to claim 1 or 2, wherein in the contact region between the wall portion of the recess in the first fiber layer and the second fiber layer, there is a fiber fusion portion at the intersection of the fibers of the wall portion and the fibers of the second fiber layer.

5. The nonwoven fabric for absorbent articles according to claim 1 or 2, wherein the lower edge of the raised portion is connected to the contact area between the wall portion and the second fiber layer in the first fiber layer.

6. The nonwoven fabric for absorbent articles according to claim 1 or 2, wherein in the contact region between the wall portion of the first fiber layer and the second fiber layer, the fibers of the second fiber layer are oriented in the planar direction of the nonwoven fabric, and the fibers on the surface of the hem portion of the raised portion have a different fiber orientation from the fibers of the wall portion.

7. Weight: 20 g / m ２ More than 100g / m ２ The nonwoven fabric for absorbent articles according to claim 1 or 2, which is as follows:

8. 4.9 mN / cm ２ The nonwoven fabric for absorbent articles according to claim 1 or 2, wherein the thickness under load is 0.8 mm or more and 10 mm or less.

9. The nonwoven fabric for absorbent articles according to claim 1 or 2, wherein the fibers of the wall portion are oriented in the thickness direction of the nonwoven fabric.

10. An absorbent article having the nonwoven fabric for absorbent articles described in claim 1 or 2.

11. A pressing step is performed in which a first fiber web is placed on a support having an uneven shape with multiple protrusions and recesses between the protrusions, the first fiber web is pressed along the recesses by the pressing portion of a pressing member to shape it, and holes are made in the first fiber web at locations corresponding to the protrusions, thereby forming an uneven, perforated fiber web having an open surface on the side opposite to the support, After removing the pressing member from the support, a first hot air is blown onto the uneven perforated fiber web to fuse the fibers together and obtain an uneven perforated nonwoven fabric. A step of supplying a second fiber web and laminating the second fiber web onto the side of the uneven perforated nonwoven fabric that is pressed into the recess of the support, A method for manufacturing a nonwoven fabric for absorbent articles, comprising: a heat fusion step of blowing a second hot air to fuse the fibers of the uneven perforated nonwoven fabric and the second fiber web together, and fusing the fibers within the second fiber web together.

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