Non-woven fabric for absorbent article

Abstract

Provided is a non-woven fabric for an absorbent article, the non-woven fabric comprising a first fiber layer and a second fiber layer laminated in the thickness direction, the first fiber layer having a concavo-convex structure provided with a plurality of convex portions and a bottom portion provided between adjacent convex portions, and the second fiber layer having a concavo-convex structure provided between adjacent convex portions, the first fiber layer including a fused fiber portion located at the intersecting portion of the fibers, and the second fiber layer including a fused fiber portion located at the intersecting portion of the fibers. Each of the plurality of protrusions has a top portion and a wall portion supporting the top portion, an open hole portion penetrating in the thickness direction is disposed in the bottom portion, and the second fiber layer is disposed on the side of the first fiber layer having the bottom portion. The second fiber layer has, on a surface side facing the first fiber layer, a protruding portion that enters from the open hole portion of the first fiber layer into a region partitioned by the wall portion.

Description

Technical Field

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

[0002] Nonwoven fabrics are used in various applications such as components of absorbent articles such as diapers and sanitary napkins. For example, nonwoven fabrics used as surface sheets of absorbent articles have various structures.

[0003] For example, Patent Document 1 describes a nonwoven fabric having a concave-convex structure with a plurality of ridges and a bottom, and with openings arranged at the bottom, as a surface sheet of an absorbent article. Patent Document 2 describes a nonwoven fabric formed by laminating a first nonwoven fabric layer and a second nonwoven fabric layer. The first nonwoven fabric layer has a concave-convex structure, and the second nonwoven fabric layer is substantially flat.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2020-467

[0007] Patent Document 2: Japanese Patent Application Publication No. 2019-44293 Summary of the invention

[0008] 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 a fiber fusion portion located at the intersection of fibers. The first fiber layer has a concave-convex structure with a plurality of convex portions and a bottom provided between adjacent convex portions, each of the plurality of convex portions has a top and a wall portion supporting the top, an opening portion penetrating in the thickness direction is arranged at the bottom, the second fiber layer is provided on the side of the first fiber layer having the bottom, and the second fiber layer has a protrusion on the side facing the first fiber layer that enters the area divided by the wall portion from the opening portion of the first fiber layer.

[0009] In addition, the present invention provides a method for manufacturing non-woven fabrics for absorbent articles, the manufacturing method comprising: placing a first fiber web on a support body having a concave-convex shape with a plurality of protrusions and concave portions between the protrusions, using a pressing portion of a pressing member to press the first fiber web along the concave portions to shape it, and opening holes at locations corresponding to the protrusions to form a concave-convex open-pore fiber web having an open-pore surface on the side opposite to the support body; after removing the pressing member from the support body, blowing a first hot air to the concave-convex open-pore fiber web to fuse the fibers with each other to obtain a concave-convex open-pore non-woven fabric; supplying a second fiber web and laminating it on the open-pore surface side of the concave-convex open-pore non-woven fabric; and blowing a second hot air to fuse the fibers of the concave-convex non-woven fabric with the fibers of the second fiber web with each other, and a thermal fusion process to fuse the fibers in the second fiber web with each other.

[0010] The above and other features and advantages of the present invention will be further clarified from the following description with appropriate reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a cross-sectional view schematically showing a preferred embodiment of the nonwoven fabric for absorbent articles of the present invention.

[0012] Figure 2 (A) is a cross-sectional view schematically showing a laminate in which an example of the nonwoven fabric for absorbent articles according to the present embodiment is placed on an absorbent body, and (B) is a photograph in lieu of a drawing of the laminate in (A) taken from the nonwoven fabric side for absorbent articles.

[0013] Figure 3 (A) is a cross-sectional view schematically showing a laminated body in which a conventional nonwoven fabric for absorbent articles is placed on an absorbent body, and (B) is a photograph in lieu of a drawing of the laminated body of (A) taken from the nonwoven fabric side for absorbent articles.

[0014] Figure 4 (A) is a cross-sectional view schematically showing a laminated body in which another conventional nonwoven fabric for absorbent articles is placed on an absorbent body, and (B) is a photograph in lieu of a drawing of the laminated body of (A) taken from the nonwoven fabric side for absorbent articles.

[0015] Figure 5 This is a plan view schematically showing a specific example of the nonwoven fabric for absorbent articles according to the present embodiment from one surface side.

[0016] Figure 6 yes Figure 5 The shown figure is a cross-sectional view of the nonwoven fabric for absorbent articles taken along line R1-R1.

[0017] Figure 7 yes Figure 5The shown figure is a cross-sectional view of the nonwoven fabric for absorbent articles taken along line R2-R2.

[0018] Figure 8 yes Figure 5 The shown figure is a cross-sectional view of the nonwoven fabric for absorbent articles taken along line R3-R3.

[0019] Fig. 9 It is an explanatory diagram schematically showing a preferred embodiment of the method for manufacturing nonwoven fabric for absorbent articles of the present invention, (A) shows a pressing process, (B) shows a process of obtaining a concave-convex open-pore nonwoven fabric by using a first hot air, (C) shows a process of laminating a second fiber web on the concave-convex open-pore nonwoven fabric, and (D) shows a process of integrating the concave-convex open-pore nonwoven fabric with the second fiber web by using a second hot air to convert the second fiber web into a nonwoven fabric.

[0020] Fig.10 is a top view of the support body.

[0021] Fig.11 It is a top view of the pressed component.

[0022] Fig.12 It is a plan view showing a state where the support body and the press-fit member are combined.

[0023] Fig.13 (A) means to use Fig. 9 The figure is a substitute photograph of an example of a cross-section in the thickness direction of a nonwoven fabric obtained by the manufacturing method of a nonwoven fabric for absorbent articles of the present embodiment shown, and (B) is a substitute photograph of an example of a cross-section in the thickness direction of a nonwoven fabric for absorbent articles obtained by a conventional manufacturing method of stacking nonwoven fabrics and integrating concave and convex open-pore nonwoven fabrics.

[0024] Fig.14 Yes Fig.13 (A) is a photograph in lieu of a drawing showing a partially enlarged view of the cross section.

[0025] Fig.15 Yes Fig.13 (B) is a photograph in lieu of a drawing showing a partially enlarged view of the cross section. DETAILED DESCRIPTION

[0026] The present invention relates to a nonwoven fabric for absorbent articles capable of improving the visibility of an opening portion arranged at a bottom of a concavo-convex structure.

[0027] When a nonwoven fabric having an open hole at the bottom of the concavo-convex structure is used as a surface sheet of an absorbent article, the presence of the open hole can improve the liquid absorbency of the absorbent article. The open hole mentioned here includes holes that penetrate in the thickness direction and holes with a concave bottom. The strength of the liquid absorbency can be easily understood by the user who holds the absorbent article in his hand by recognizing the open hole structure.

[0028] However, when the nonwoven fabric is used as a surface sheet in an absorbent article, the opening is difficult to be seen due to the presence of the lower layer member. Therefore, from the perspective of the strength of liquid absorbency required of the user, it is desired that the bottom opening of the nonwoven fabric has high visibility.

[0029] In contrast, the nonwoven fabric for absorbent articles of the present invention can improve the visibility of the openings arranged at the bottom of the concavo-convex structure. According to the method for producing the nonwoven fabric for absorbent articles of the present invention, the nonwoven fabric for absorbent articles of the present invention can be suitably produced.

[0030] A preferred embodiment of the nonwoven fabric for absorbent articles of the present invention will be described below with reference to the drawings. In addition, in this specification, the nonwoven fabric for absorbent articles may be simply referred to as nonwoven fabric.

[0031] The nonwoven fabric 10 of the present embodiment is a so-called thermally bonded nonwoven fabric having a fiber fusion portion at the intersection of the fibers. For example, a hot air nonwoven fabric in which the fiber fusion portion is formed by a hot air method can be cited. Therefore, the nonwoven fabric 10 contains thermoplastic fibers in the constituent fibers. That is, the first fiber layer M1 and the second fiber layer M2 described later constituting the nonwoven fabric 10 contain thermoplastic fibers in the constituent fibers and are nonwoven fabrics formed with the fiber fusion portion. The first fiber layer M1 and the second fiber layer M2 are integrated by the fiber fusion portion located at the intersection of the fibers.

[0032] Such a nonwoven fabric 10 of the present embodiment is as follows Figure 1As shown, the nonwoven fabric 10 has a first fiber layer M1 and a second fiber layer M2 stacked in the thickness direction. The nonwoven fabric 10 has a surface side 10T and a surface side 10B and a back side, and the first fiber layer M1 is arranged on the one surface side 10T, and the second fiber layer M2 is arranged on the other surface side 10B. In the nonwoven fabric 10, for example, one surface side 10T can be set as the use surface. For example, when the nonwoven fabric 10 is used as a surface sheet of an absorbent article, one surface side 10T can be set as the skin surface 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. It should be noted that the above-mentioned one surface side 10T and the other surface side 10B mean the surface and back of the entire nonwoven fabric 10, and also mean the surface and back of each of the first fiber layer M1 and the second fiber layer M2. In addition, 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.

[0033] The first fiber layer M1 has a plurality of protrusions 1 protruding from one surface side 10T and a bottom portion 2 provided between adjacent protrusions 1, 1. Thus, the first fiber layer M1 has a concavo-convex structure in the thickness direction Z. The protrusions 1 are three-dimensional fiber layers vertically provided along the thickness direction Z of the first fiber layer M1, and are located at a higher position on one surface side 10T than the bottom portion 2. Each of the plurality of protrusions 1 has a top portion 1A and a wall portion 1B supporting the top portion 1A.

[0034] The top 1A may have a flat or curved outer shape. The top 1A preferably has a flat surface to facilitate recognition of the depth of the unevenness and to make the shadow around the opening 3 in the bottom 2 clearer.

[0035] The end portion (also referred to as the root portion 1D) of the other side 10B of the wall portion 1B abuts against the second fiber layer M2. In the abutting 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 the second fiber layer M2 and integrated (fixed). Regarding this integration, from the viewpoint of improving the bonding strength and maintaining the concavo-convex shape of the first fiber layer M1, it is preferred to integrate the root portion 1D of the wall portion 1B with the second fiber layer M2 by using a fiber fusion portion located at the intersection of the constituent fibers of the root portion 1D of the wall portion 1B and the constituent fibers of the second fiber layer M2.

[0036] The fibers of the wall portion 1B are preferably oriented longitudinally relative to the plane of the other surface side 10B of the nonwoven fabric 10 (the second fiber layer M2). The longitudinal orientation of the fibers increases the supporting force of the top 1A and the second fiber layer M2 in the thickness direction of the wall portion 1B, and the thickness of the convex portion 1 of the nonwoven fabric 10 is easily retained even under load. As a result, the nonwoven fabric 10 including the first fiber layer M1 and the second fiber layer M2 is easy to retain thickness, and has excellent cushioning properties due to the elasticity brought by the fiber structure of the fiber layer. That is, the nonwoven fabric 10 has excellent softness with a touch. In addition, when the nonwoven fabric 10 is used as a member closer to the skin side relative to the absorbent in an absorbent article, such as a surface sheet, the liquid permeation effect of body fluid is easier to continue even under load, and the liquid back permeation (wet back) from the absorbent to the skin side is suppressed. The three-dimensional shape of the wall portion 1B that functions in this way can be well maintained by integrating with the second fiber layer M2 with high strength using the aforementioned fiber fusion portion. In addition, since the integration utilizes the bonding state based on the fiber fusion portion located at the intersection of the fibers, it is not necessary to destroy the lower part of the wall 1B to ensure the bonding surface as in the case of conventional bonding using hot melt adhesives, etc. Thus, the height of the wall 1B can be maintained at a sufficient height.

[0037] The so-called longitudinal orientation of the fibers of the wall portion 1B means that there are many fibers along the thickness direction Z of the first fiber layer M1, and that the longitudinal orientation rate obtained by the measurement method described later is 60% or more. From the viewpoint of further improving the above-mentioned effect, it is preferably 61% or more, and more preferably 62% or more. In addition, there is no particular restriction on the upper limit of the longitudinal orientation rate, but from the viewpoint of forming a fusion point by creating a cross section between the fibers and forming a columnar structure with the fibers to bear force, it is preferably 90% or less, more preferably 85% or less, and even more preferably 80% or less.

[0038] (Method for measuring longitudinal orientation ratio of fibers in wall portion 1B)

[0039] like Figure 1 As shown, the wall portion 1B is measured according to the following procedure.

[0040] That is, the fiber layer section of the wall portion 1B defined in the cross section of the nonwoven fabric 10 in the thickness direction, including the convex portion 1 of the first fiber layer M1 and the second fiber layer M2, is observed by magnifying it 35 times using a scanning electron microscope (SEM). A line of a square with a side length of 500 μm is marked in the observed image as a reference line. Each side (reference line) of the square is set as a side orthogonal to the thickness direction and the plane direction in the cross section of the nonwoven fabric 10. The number of extended fibers passing through the reference line composed of each side of the square is counted respectively. The fibers passing through the square reference line orthogonal to the plane direction of the nonwoven fabric 10 are defined as the "number of transverse fibers", and the fibers passing through the square reference line orthogonal to the thickness direction of the nonwoven fabric 10 are defined as the "number of longitudinal fibers". As the longitudinal orientation rate, (number of longitudinal fibers) / (number of transverse fibers + number of longitudinal fibers)×100=longitudinal orientation rate (%) is calculated. These are measured at 10 points each, and the average value is set as the value of the longitudinal orientation rate.

[0041] It should be noted that the plane direction in the cross section of the nonwoven fabric 10 is equivalent to Figure 1 The thickness direction corresponds to the direction Z perpendicular to the straight line L which is in contact with the surface of the other surface side 10B of the second fiber layer M2.

[0042] In the cross section of the nonwoven fabric 10 in the thickness direction Z including the protrusions 1 and the bottom 2 of the first fiber layer M1 described above, the fiber layer of the wall portion 1B can be divided by the following method.

[0043] That is, a nonwoven fabric having a cross section in the thickness direction including the top 1A of the first fiber layer M1, the wall 1B, and the second fiber layer M2 is placed on the base of a microscope VHX6000 (trade name, manufactured by KEYENCE Co., Ltd.) with the second fiber layer M2 (the other surface side 10B) facing downward. Then, a flat plate (e.g., an acrylic plate) is placed on the top 1A side (one surface side 10T) of the nonwoven fabric and a force of 4.9 mN / cm is applied. 2 In this state, the cross section in the thickness direction Z is observed using the microscope at 20 times, and the portion of the first fiber layer M1 in contact with the flat plate is defined as the top portion 1A. The portion connecting the end portion of the top portion 1A and the surface of one surface side 10T of the second fiber layer M2 is defined as the wall portion 1B.

[0044] When determining the boundary between the top 1A and the wall 1B, the thickness of the top 1A in the portion where the wall 1B does not exist is defined as the thickness of the end of the top 1A, and the portion other than this thickness is defined as the wall 1B.

[0045] The bottom 2 of the first fiber layer M1 is provided between adjacent convex portions 1, 1, and more specifically, refers to a region including the bottom of a concave portion (concave portion 2U between convex portions) that is concave toward the other side 10B between the convex portions 1, 1 and the end portion (root 1D) of the other side 10B of the wall portion 1B. The bottom 2 is provided with an opening portion 3 that penetrates in the thickness direction Z. It should be noted that in Figure 1 In the example shown, the entire bottom portion 2 except the root portion 1D becomes the opening portion 3, and in this case, the root portion 1D of the wall portion 1B becomes the bottom portion 2. The penetration of the opening portion 3 mentioned here, when focusing on the first fiber layer M1, means that the portion of the first fiber layer M1 where no constituent fibers are arranged penetrates both surfaces of the first fiber layer M1 along the thickness direction Z.

[0046] The openings 3 are different from the fine pores formed between the fibers. They are holes formed by processing the first fiber layer M1 and have a hole area much larger than the fine pores formed between the fibers. Figure 1 Although the entire portion except the root 1D of the bottom 2 is shown as the opening portion 3, the size of the opening portion 3 can be appropriately selected according to the width of the bottom 2. For example, in the first fiber layer M1, the entire portion except the root 1D of the bottom 2 can be set as the opening portion 3, and a fiber layer extending from the root 1D can exist around the opening portion 3. It is preferred to have at least 1.0 mm 2 The size of the opening 3 can be measured using the microscope described above. Specifically, the area of ​​the opening 3 at 10 locations is measured using a microscope, and the average value thereof is set as the hole area of ​​each opening.

[0047] The area of ​​the opening 3 is preferably 1.0 mm from the viewpoint of improving the liquid permeability. 2 More preferably 1.5 mm 2 More preferably, 2.0 mm 2 In addition, the area of ​​the opening 3 is preferably 50 mm from the viewpoint of suppressing liquid re-seepage. 2 Below, more preferably 40mm 2 Below, more preferably 35mm 2 the following.

[0048] The planar shape of the opening 3 can be various planar shapes from the viewpoint of improving liquid permeability, and examples thereof include a circular shape, an elliptical shape, and a rectangular shape.

[0049] The second fiber layer M2 is arranged on the side with the bottom of the first fiber layer M1, and has a raised portion 5 that enters the area divided by the wall portion 1B from the opening portion 3 of the first fiber layer M1 on the surface side facing the first fiber layer M1. That is, the raised portion 5 is located on one surface side 10T compared to the root 1D of the wall portion 1B in the above-mentioned contact area 4, and is in a space sandwiched by the wall portion 1B between the convex portions 1, 1 of the first fiber layer M1. On the other hand, the second fiber layer M2 in the contact area 4 adjacent to the raised portion 5 becomes a recessed portion 6 due to the embedding of the wall portion 1B.

[0050] Since the raised portion 5 enters the first fiber layer M1 at the position of the opening portion 3 that penetrates the first fiber layer M1 in the thickness direction Z, it can be observed from one side of the first fiber layer M1. Therefore, when the nonwoven fabric 10 is observed from one side (one surface side 10T) of the first fiber layer M1, it can be observed that the convex portion 1 of the first fiber layer M1 is adjacent to the raised portion 5 of the second fiber layer M2. At this time, due to the presence of the valley formed by the root 1D of the wall portion 1B constituting the convex portion 1 and the lower edge portion 7 of the raised portion 5 extending to the root 1D, the shadow around the opening portion 3 at the bottom 2 of the first fiber layer M1 is emphasized. With respect to this shadow, when the fibers of the wall portion 1B are longitudinally oriented, the raised portion 5 becomes a fiber layer having a fiber orientation different from that of the wall portion 1B, and a dividing line is formed between the two portions where the fiber orientation degree changes discontinuously, thereby further emphasizing the display. In this way, the raised portion 5 can be observed from one side of the first fiber layer M1, so that consumers of absorbent articles having the nonwoven fabric 10 as a surface sheet can visually understand that clear openings are formed in the nonwoven fabric. As a result, consumers can think that the article is an absorbent article with excellent liquid absorbency and can use the article with peace of mind.

[0051] It should be noted that in Figure 1 In the example shown, the entire portion of the bottom 2 except the root 1D is formed into the opening portion 3, and the lower edge portion 7 of the raised portion 5 is directly connected to the root 1D of the wall portion 1B. However, this is not limited to this method, and a fiber layer may exist around the opening portion 3 in the recessed portion 2U between the convex portions of the first fiber layer M1. In this case, the lower edge portion 7 of the raised portion 5 of the second fiber layer M2 extends to the root 1D of the wall portion 1B via the fiber layer around the opening portion 3 in the recessed portion 2U between the convex portions, forming the above-mentioned valley, thereby forming the above-mentioned dividing line.

[0052] In the nonwoven fabric 10 , due to the enhanced display of the above-mentioned shadow, the visibility of the opening portion 3 when viewed from one side (one surface side 10T) of the first fiber layer M1 is improved.

[0053] In particular, when the nonwoven fabric 10 is placed as the surface sheet of the absorbent article on the skin side of the absorbent, the shadow around the opening 3 of the nonwoven fabric 10 is further enhanced relative to the white background of the absorbent, and the high absorption capacity of the absorbent article becomes apparent due to the significant improvement in the visibility of the opening 3.

[0054] In this regard, it is also possible to Figures 2 to 4 The case where the nonwoven fabric is placed as the top sheet on the absorbent body can be understood by comparing the state of the openings on the nonwoven fabric side (one surface side 10T). Figures 2 to 4 The results are shown when only the nonwoven fabric used as the top sheet was different and the photographing position and angle and the lighting position and angle were the same. Figure 2 The nonwoven fabric used as the surface sheet is a nonwoven fabric 10S which is an example of the nonwoven fabric 10 of the present embodiment. Figure 3 The nonwoven fabric used as the top sheet is a conventional nonwoven fabric C1 composed only of the first fiber layer M1 having no openings 3 . Figure 4 The nonwoven fabric used as the top sheet is a conventional nonwoven fabric C2 composed only of the first fiber layer M1 having the openings 3 .

[0055] Figure 2 In the nonwoven fabric 10S as an example of the present embodiment, the shadows around the openings 3 when viewed from one side (one surface side 10T) of the first fiber layer M1 are the same as those of the nonwoven fabric 10S. Figure 3 and Figure 4 The display is clearly more strongly enhanced than the illustrated situation, and the visibility of the opening 3 is significantly improved.

[0056] Due to this visibility, in an absorbent article in which the nonwoven fabric 10 is incorporated as a top sheet, consumers can easily recognize the good liquid permeability through the openings 3 of the top sheet, that is, the good absorbency of the absorbent article.

[0057] In addition, in the nonwoven fabric 10, due to the presence of the ridges 5 of the second fiber layer M2 entering the first fiber layer M1, the transfer of liquid from the first fiber layer M1 to the second fiber layer M2 becomes smoother through the openings 3. As a result, in an absorbent article in which the nonwoven fabric 10 is incorporated as a surface sheet, the liquid permeability of the surface sheet becomes even better, and liquid re-permeation is further suppressed, making it less likely that liquid will remain on the skin.

[0058] From the viewpoint of making the shadow between the root 1D of the wall portion 1B and the raised portion 5 more effectively enhanced, it is preferred that the surface side of the second fiber layer M2 facing the first fiber layer M1 is a continuous fiber layer extending in the plane direction. By making the surface side of the second fiber layer M2 facing the first fiber layer M1 a continuous fiber layer extending in the plane direction, the aforementioned shadow portion becomes more noticeable as a portion of different properties in the above-mentioned continuous fiber layer. In addition, when the fibers of the wall portion 1B of the first fiber layer M1 are longitudinally oriented, a dividing line where the fiber orientation changes discontinuously is formed in the first fiber layer M1 and the second fiber layer M2, and the shadow is enhanced.

[0059] From the same point of view, it is preferred that the lower edge portion 7 descending from the raised portion of the raised portion 5 is connected to the contact area 4 between the wall portion 1B in the first fiber layer M1 and the second fiber layer M2. By connecting the lower edge portion 7 to the contact area 4 in this way and forming a valley using the root 1D of the wall portion 1B and the lower edge portion 7, the shadow around the opening portion 3 located at the bottom 2 of the first fiber layer M1 is further enhanced.

[0060] From the viewpoint of making the above-mentioned shadow reinforcement display more clear, in the contact area 4 between the wall portion 1B in the first fiber layer M1 and the second fiber layer M2, it is preferred that the fibers of the second fiber layer M2 are oriented in the planar direction, and the fibers on the surface of the lower edge portion 7 of the raised portion 5 have a fiber orientation different from that of the fibers of the wall portion 1B. By making the fibers on the surface of the lower edge 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 in which the fiber orientation of the surface of the lower edge portion 7 and the fiber orientation of the wall portion 1B change discontinuously, and the shadow is reinforced.

[0061] It should be noted that the fibers on the surface of the lower edge 7 of the raised portion 5 refer to the fibers that rise from the root 1D of the wall 1B located in the contact area 4. For example, the fibers on the surface of the raised portion 5 within a range of 2 mm from the root 1D toward the lower edge 7 in the planar direction.

[0062] Specifically, the longitudinal orientation rate of the fiber orientation on the surface of the lower edge portion 7 is less than 45%. A longitudinal orientation rate of less than 45% means that the fibers are oriented in the planar direction, which is a longitudinal orientation rate different from that of the fibers of the wall portion 1B, so that the above-mentioned shadow can be made clear. Here, the fibers on the surface of the lower edge portion 7 have a fiber orientation different from that of the fibers of the wall portion 1B, which means that the difference in the longitudinal orientation rate between the two is 15% or more. From the viewpoint of further improving the above-mentioned effect, it is preferably 20% or more, and more preferably 30% or more.

[0063] (Method for measuring longitudinal orientation ratio of fibers on the surface of lower edge portion 7)

[0064] like Figure 1 As shown, the lower edge portion 7 is measured according to the following steps.

[0065] That is, the cross section of the fiber layer including the lower edge portion 7 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 by magnifying it 35 times using a scanning electron microscope (SEM). A line of a square with a side length of 500 μm is marked as a reference line in the observed image. At this time, the line is marked in such a way that the fibers of the lower edge portion 7 are included in the entire area within the square. Each side (reference line) of the square is set as a side orthogonal to the thickness direction and the plane direction in the cross section of the nonwoven fabric 10. The number of extended fibers passing through the reference line composed of each side of the square is counted respectively. The fibers passing through the reference line of the square orthogonal to the plane direction of the nonwoven fabric 10 are defined as the "number of transverse fibers", and the fibers passing through the reference line of the square orthogonal to the thickness direction of the nonwoven fabric 10 are defined as the "number of longitudinal fibers". As the longitudinal orientation rate, (number of longitudinal fibers) / (number of transverse fibers+number of longitudinal fibers)×100=longitudinal orientation rate (%) is calculated. These longitudinal orientation ratios were measured at 10 points each, and the average value was made into the value of the longitudinal orientation ratio.

[0066] From the viewpoint of further strengthening the above-mentioned shadow display, the ratio (H2 / H1) of the thickness H2 of the protrusion 5 to the thickness H1 of the first fiber layer M1 is preferably 0.05 or more, more preferably 0.10 or more, and even more preferably 0.15 or more.

[0067] 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.

[0068] It should be noted that the thickness H1 of the first fiber layer M1 refers to the height from the surface of one surface side 10T of the top portion 1A to the boundary between the root 1D of the wall portion 1B in the contact area 4 and the second fiber layer M2. 2 Under the load state, this definition can be performed in the same manner as the division method of the fiber layer of the wall portion 1B described above.

[0069] The basis weight of the nonwoven fabric 10 is preferably 20 g / m2 from the viewpoint of improving the texture of the nonwoven fabric and enhancing the shadow of the openings. 2 More preferably 30g / m 2 More preferably, 40 g / m 2 In addition, the basis weight of the nonwoven fabric 10 is preferably 100 g / m2 from the viewpoint of not hindering the comfortable feeling of the wearer. 2Below, more preferably 90g / m 2 Below, more preferably 85g / m 2 the following.

[0070] About 4.9mN / cm of nonwoven fabric 10 2 (0.05gf / cm 2 ) The thickness under load is preferably 0.8 mm or more, more preferably 1.0 mm or more, and further preferably 1.2 mm or more from the viewpoint of further strengthening the shadow of the opening portion. The thickness can be 4.9 mN / cm 2 The load is measured using a laser displacement meter or the like. The above-mentioned 4.9 mN / cm 2 The load is assumed to be a load on the surface of the nonwoven fabric. 2 When the thickness under load is within the above range, the liquid back-seepage prevention performance is improved and the wearer's skin is less likely to be wetted.

[0071] In addition, regarding the 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 hindering the comfortable feeling of use of the wearer.

[0072] The fiber diameter of the fibers of the second fiber layer M2 is preferably larger than the fiber diameter of the fibers of the first fiber layer M1. Thus, fibers thicker than those of the first fiber layer M1 are exposed as protrusions 5 from the openings 3 of the first fiber layer M1, and the permeability of low-viscosity excretion fluids such as urine through the openings 3 can be improved.

[0073] From this viewpoint, the ratio (D2 / D1) of the fiber diameter (D2) of the fibers of the second fiber layer M2 to the fiber diameter (D1) of the fibers 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. In addition, the above ratio (D2 / D1) is preferably 10.0 or less, more preferably 9.0 or less, and even more preferably 8.0 or less, from the viewpoint of making the texture of the raised portion 5 good and enhancing the shadow of the open portion.

[0074] Furthermore, within the range satisfying the above ratio (D2 / D1), the fiber diameter (D2) of the fibers of the second fiber layer M2 is preferably 15 μm or more, more preferably 20 μm or more, and further preferably 25 μm or more, from the viewpoint of improving the liquid permeability of low-viscosity excretion fluids such as urine from the opening 3. Furthermore, the fiber diameter (D2) of the fibers of the second fiber layer M2 is preferably 80 μm or less, more preferably 70 μm or less, and further preferably 60 μm or less, from the viewpoint of improving the texture of the raised portion 5 and enhancing the shadow of the opening.

[0075] In the range satisfying the above ratio (D2 / D1), the fineness (D1) of the fibers of the first fiber layer M1 is preferably 8 μm or more, more preferably 10 μm or more, and further preferably 12 μm or more from the viewpoint of achieving good texture. In addition, the fiber diameter (D1) of the fibers of the first fiber layer M1 is preferably 40 μm or less, more preferably 30 μm or less, and further preferably 20 μm or less from the viewpoint of maintaining softness.

[0076] The above-mentioned fiber diameter means the average fiber diameter of each fiber layer.

[0077] (Method for measuring the average fiber diameter of each fiber layer)

[0078] The fiber diameter can be measured by observing the cross section of the fiber layer using the following method.

[0079] The part of the measurement object (e.g., the first fiber layer M1) is frozen in a no-load state using cold spray or liquid nitrogen to fix the structure, and in this state, a cutting blade is used to cut along the thickness direction to expose the cross section of the measurement part. A scanning electron microscope (JCM-5100 manufactured by JEOL Ltd.) is used to enlarge the cross section and observe it, and the magnification (300 times) of the fiber cross section can be adjusted to be able to measure the fiber cross section. Five observation photos taken in this state are taken to obtain cross-sectional observation photos. Then, the fiber diameters of 30 fibers are measured in each photo, and the arithmetic mean thereof is set as the average fiber diameter of the present invention. When the fiber is not a perfect circle, two points on the periphery of the cross section are connected, and the line segment with the maximum diameter length of the cross section is defined as the major axis, and the line segment with the maximum length orthogonal to the major axis is defined as the minor axis. Thereafter, the lengths of the major axis and the minor axis are analyzed and calculated using image analysis software, thereby measuring the lengths of the major axis and the minor axis of each fiber, and the arithmetic mean of the major axis length and the minor axis length in one fiber is set as the fiber diameter of each fiber, and the arithmetic mean of 30 fiber diameters is set as the average fiber diameter of the fiber of the present invention.

[0080] When the nonwoven fabric to be measured is incorporated into a sanitary product such as an absorbent article, a cold spray is blown onto the sanitary product to cure the hot melt adhesive, and then the nonwoven fabric to be measured is carefully peeled off. This method is also common to other measurements in this specification.

[0081] On the other hand, the constituent fibers of the second fiber layer M2 preferably have a smaller fiber diameter than the constituent fibers of the first fiber layer M1. In the combination with the wall portion 1B and the opening portion 3, this arrangement is particularly effective for improving the permeability of high-viscosity excretion fluids such as soft stools and menstrual blood that are easily retained in one position. It should be noted that the so-called high viscosity mentioned above means greater than 5 cP. By making the fiber diameter small, the number of fibers per unit area of ​​the second fiber layer M2 is increased compared with the first fiber layer M1, the capillary force between the fibers is increased, and the difference in capillary force between the second fiber layer M1 and the first fiber layer M1 becomes larger. Such a second fiber layer M2 becomes exposed to one side of the first fiber layer M1 in the aforementioned opening portion 3. That is, the second fiber layer M2 with a stronger capillary force is not covered by the first fiber layer M1 in the opening portion 3, but becomes an exposed state that can be observed from one side 10T. Thus, the nonwoven fabric 10 has a structure in which the capillary force enhanced in the second fiber layer M2 spreads to one side of the first fiber layer M1 via the opening 3. With this structure, in the opening 3, the force of introducing the high-viscosity excrement liquid that descends along the wall 1B into the second fiber layer M2 is increased. Moreover, the second fiber layer M2 can use its strong capillary force to diffuse the introduced high-viscosity excrement liquid to the other side 10B of the nonwoven fabric 10. Thus, the liquid permeation rate of the high-viscosity excrement liquid from the first fiber layer M1 to the second fiber layer M2 and the residual liquid prevention property in the first fiber layer M1 are improved, and the liquid permeability in the thickness direction of the nonwoven fabric 10 is improved. In addition, the liquid back-permeation of the high-viscosity excrement liquid from the second fiber layer M2 to the first fiber layer M1 is suppressed.

[0082] From the viewpoint of making the aforementioned action brought about by the aforementioned difference in capillary force more efficient, the difference (E1-E2) between the fiber diameter (E1) of the constituent fibers of the first fiber layer M1 and the fiber diameter (E2) of the constituent fibers of the second fiber layer M2 is preferably 2 μm or more, more preferably 3 μm or more, and further preferably 4 μm or more. In addition, from the viewpoint of improving the clarity of the opening portion, the aforementioned difference (E1-E2) is preferably 50 μm or less, more preferably 40 μm or less, and further preferably 30 μm or less. The constituent fibers of the second fiber layer M2 having a finer fiber diameter than the constituent fibers of the first fiber layer M1 are exposed to the first fiber layer side in the opening portion 3. Near the opening portion 3, the wall portion 1B and / or the bottom portion 2 composed of the constituent fibers of the first fiber layer M1 and the constituent fibers of the second fiber layer M2 form a structure that is more locally entangled due to the difference in fiber diameter. This structure can not only improve the clarity of the opening portion, but also improve the force of introducing excrement compared to a laminated nonwoven fabric with no exposed portion obtained by simply laminating two types of fiber layers.

[0083] In addition, within the range satisfying the above-mentioned difference (E1-E2), the fiber diameter (E2) of the constituent fibers of the second fiber layer M2 is preferably 25 μm or less, more preferably 20 μm or less, and further preferably 18 μm or less from the viewpoint of improving capillary force. The fiber diameter (E2) of the constituent fibers of the second fiber layer M2 is preferably 3 μm or more, more preferably 5 μm or more, and further preferably 8 μm or more from the viewpoint of further improving liquid permeability.

[0084] In addition, within the range satisfying the above-mentioned difference (E1-E2), the fiber diameter (E1) of the constituent fibers of the first fiber layer M1 is preferably 5 μm or more, more preferably 6 μm or more, and further preferably 8 μm or more from the viewpoint of achieving a good texture. The fiber diameter (E1) of the constituent fibers of the first fiber layer M1 is preferably 25 μm or less, more preferably 23 μm or less, and further preferably 20 μm or less from the viewpoint of achieving a better skin feel.

[0085] It should be noted that the above-mentioned fiber diameter means the average fiber diameter of each of the constituent fibers of the first fiber layer M1 and the second fiber layer M2.

[0086] (Method for measuring average fiber diameter of constituent fibers of the first fiber layer M1 and the second fiber layer M2)

[0087] The fiber diameter can be measured by observing the cross section of the fiber layer using the following method.

[0088] The part to be measured (e.g., the first fiber layer M1) is frozen in a no-load state using cold spray or liquid nitrogen to fix the structure, and in this state, a cutting blade is used to cut along the thickness direction to expose the cross section of the measurement part. A scanning electron microscope (JCM-5100 manufactured by JEOL Ltd.) is used to magnify and observe the cross section, and the magnification (100 to 500 times) is adjusted to be able to measure the fiber cross section. Five observation photos taken in this state are taken to obtain cross-sectional observation photos.

[0089] Then, the center of the thickness direction of each of the first fiber layer M1 and the second fiber layer M2 is set as the measurement position, and the fiber diameters of 30 fibers are measured in each photo, and the arithmetic mean thereof is set as the average fiber diameter of the present invention. In the case where the fiber is not a perfect circle, two points on the periphery of the cross section are connected, and the line segment with the maximum diameter length of the cross section is defined as the major axis, and the line segment with the maximum length orthogonal to the major axis is defined as the minor axis. Thereafter, the lengths of the major axis and the minor axis are analyzed and calculated using image analysis software, and the lengths of the major axis and the minor axis of each fiber are measured, and the arithmetic mean of the major axis length and the minor axis length in one fiber is set as the fiber diameter of each fiber, and the arithmetic mean of the 30 fiber diameters is set as the average fiber diameter of the fiber of the present invention.

[0090] When the nonwoven fabric to be measured is incorporated into a sanitary product such as an absorbent article, a cold spray is blown onto the sanitary product to cure the hot melt adhesive, and then the nonwoven fabric to be measured is carefully peeled off. This method is also common to other measurements in this specification.

[0091] Similarly, from the viewpoint of making the aforementioned action due to the aforementioned difference in capillary force more efficient, the number of fibers per unit area of ​​the second fiber layer M2 is preferably larger than the number of fibers per unit area of ​​the top portion 1A in the first fiber layer M1 .

[0092] More specifically, the difference (F2-F1) between the number of fibers per unit area (F2) of the second fiber layer M2 and the number of fibers per unit area (F1) of the top portion 1A of the first fiber layer M1 is preferably 5 or more, more preferably 8 or more, and even more preferably 10 or more. In addition, the difference (F2-F1) is preferably 190 or less, more preferably 185 or less, and even more preferably 180 or less, from the viewpoint of increasing the force of introducing the high-viscosity excrement liquid and promoting the transfer of the liquid to the absorbent.

[0093] Furthermore, within the range satisfying the above-mentioned difference (F2-F1), from the viewpoint of improving the capillary force, the number of fibers (F2) per unit area of ​​the second fiber layer M2 is preferably 80 or more, more preferably 85 or more, and further preferably 90 or more. From the viewpoint of further improving the permeability of the above-mentioned high-viscosity excrement fluid, the number of fibers (F2) per unit area of ​​the second fiber layer M2 is preferably 200 or less, more preferably 190 or less, and further preferably 180 or less.

[0094] In addition, within the range satisfying the above-mentioned difference (F2-F1), from the viewpoint of suppressing residual liquid, the number of fibers (F1) per unit area of ​​the top portion 1A in the first fiber layer M1 is preferably 90 or less, more preferably 85 or less, and further preferably 80 or less. From the viewpoint of achieving a better skin feel, the number of fibers (F1) per unit area of ​​the top portion 1A in the first fiber layer M1 is preferably 20 or more, more preferably 25 or more, and further preferably 30 or more.

[0095] It should be noted that the number of fibers per unit area mentioned above means an average value of the constituent fibers of each of the first fiber layer M1 and the second fiber layer M2.

[0096] (Method for measuring the number of fibers per unit area of ​​the first fiber layer M1 and the second fiber layer M2)

[0097] The number of fibers per unit area of ​​the first fiber layer M1 was measured at the center of the top portion 1A in the thickness direction, and the number of fibers per unit area of ​​the second fiber layer M2 was measured at the center of the thickness direction of the portion overlapping the opening 3 .

[0098] Specifically, the cross section of the nonwoven fabric 10 is observed and the number of fiber cross sections is measured by the following procedure.

[0099] First, for the portion to be measured, a cross section along two directions (for example, a cross section of a nonwoven fabric 20 described later) is prepared along the length direction of the nonwoven fabric 10 and the width direction orthogonal to the length direction. Figure 6 The cross section shown and Figure 7 It should be noted that, when it is not possible to form a cross section including both the top 1A of the first fiber layer M1 and the portion of the second fiber layer M2 overlapping the opening 3, the cross sections in the two directions described above may be formed for each portion.

[0100] Then, the cross section is observed under magnification (100 to 500 times) using a scanning electron microscope (JCM-6000Plus (trade name) manufactured by JEOL Ltd.) that allows measurement of cross sections of about 2 to 40 fibers. At this time, metal is vapor-deposited on the cross section.

[0101] For the top 1A of the first fiber layer M1, a certain area (0.12 mm 2 ) is divided by the certain area to convert it into per unit area (1mm 2 The average of the total of 10 points (5 points + 5 points) is defined as the number of fibers per unit area of ​​the first fiber layer M1 (fibers / mm2 ).

[0102] Similarly, for the portion of the second fiber layer M2 that overlaps the opening 3, the cross-sections in the two directions are measured and converted in the same manner as above at 5 locations. The average of the total 10 points is set as the number of fibers per unit area of ​​the second fiber layer M2 (roots / mm 2 ).

[0103] A large number of fibers per unit area means a high fiber density, which means that the capillary force acts more strongly.

[0104] From the viewpoint of further improving the force of introducing the excrement liquid into the second fiber layer M2 through the opening 3 of the first fiber layer M1, it is preferred that the hydrophilicity of the constituent fibers of the second fiber layer M2 is higher than the hydrophilicity of the constituent fibers of the first fiber layer M1. Since the constituent fibers of the second fiber layer M2, which have a higher hydrophilicity than the constituent fibers of the first fiber layer M1, are exposed to the first fiber layer side in the opening 3, the excrement liquid that descends along the wall 1B will not be retained at the bottom 3, but can be quickly introduced into the exposed portion with high hydrophilicity.

[0105] The above-mentioned "hydrophilicity" is represented by the size of the contact angle of the fiber obtained by the following measurement method. Specifically, a low hydrophilicity is synonymous with a large contact angle, and a high hydrophilicity is synonymous with a small contact angle.

[0106] The hydrophilicity, i.e., contact angle, of the constituent fibers of the first fiber layer M1 and the second fiber layer M2 can be set by surface treatment with a hydrophobic agent and a hydrophilic agent when using synthetic fibers such as thermoplastic fibers. As the hydrophilic agent and the hydrophobic agent, various preparations commonly used in such articles can be used.

[0107] It should be noted that the above-mentioned hydrophilicity means the average hydrophilicity of the constituent fibers of each of the first fiber layer M1 and the second fiber layer M2.

[0108] The difference (G1-G2) between the contact angle (G1) of the constituent fibers of the first fiber layer M1 and the contact angle (G2) of the constituent fibers of the second fiber layer M2 is preferably 0.5 or more, more preferably 1.0 or more, and even more preferably 2.0 or more from the viewpoint of further improving the above-mentioned force of introducing the excrement liquid. In addition, the above-mentioned difference (G1-G2) is preferably 50.0 or less, more preferably 45.0 or less, and even more preferably 40.0 or less from the viewpoint of improving the force of introducing the liquid and promoting the transfer of the liquid to the absorbent.

[0109] Furthermore, within the range satisfying the above-mentioned difference (G1-G2), from the viewpoint of improving the force of introducing the excrement liquid, the contact angle (G2) of the constituent fibers of the second fiber layer M2 is preferably 85 or less, more preferably 82 or less, and further preferably 80 or less. From the viewpoint of improving the force of introducing the liquid and promoting the transfer of the liquid to the absorbent body, the contact angle (G2) of the constituent fibers of the second fiber layer M2 is preferably 50 or more, more preferably 55 or more, and further preferably 60 or more.

[0110] In addition, within the range satisfying the above-mentioned difference (G1-G2), from the viewpoint of suppressing residual liquid, the contact angle (G1) of the constituent fibers of the first fiber layer M1 is preferably 60 or more, more preferably 65 or more, and further preferably 70 or more. From the viewpoint of suppressing liquid flow, the contact angle (G1) of the constituent fibers of the first fiber layer M1 is preferably 89 or less, more preferably 88 or less, and further preferably 85 or less.

[0111] (Contact angle measurement method)

[0112] Fibers were taken from three locations each of the top 1A and the wall 1B of the first fiber layer M1, and fibers were taken from three locations each of the center portion in the thickness direction of the portion overlapping with the opening 3 and the center portion in the thickness direction of the portion not overlapping with the second fiber layer M2, and the contact angle of water with respect to the fibers was measured. An automatic contact angle meter MCA-J (trade name) manufactured by Kyowa Interface Science Co., Ltd. was used as a measuring device. Distilled water was used in the measurement of the contact angle.

[0113] The amount of liquid ejected from the inkjet water droplet ejection unit (PulseInjector CTC-25 manufactured by Cluster Technology, with an ejection unit aperture of 25 μm) was set to 20 picoliters, and the water droplets were dripped directly above the fiber. The dripping state was recorded in a high-speed video recording device connected to a horizontally arranged camera. Regarding the video recording device, from the perspective of subsequent image analysis, it is preferred to install a personal computer with a high-speed capture device. In this measurement, images were recorded every 17 msec. In the recorded image, the initial image when the water droplet landed on the fiber taken out from the non-woven fabric was analyzed using the accompanying software FAMAS (the software version is 2.6.2, the analysis technique is the droplet method, the analysis method is the θ / 2 method, the image processing algorithm is non-reflection, the image processing picture mode is the frame, the threshold level is 200, and no curvature correction is performed), and the angle between the surface of the water droplet contacting the air and the fiber is calculated and set as the contact angle.

[0114] Cut the fiber taken out from the nonwoven fabric into a fiber length of 1 mm, and place the fiber on the sample stage of the contact angle meter and keep it horizontal. Measure the contact angle of two different parts of one fiber. Measure the contact angle of three different fibers to the first decimal place, and average the measured values ​​of a total of 12 parts (round off to the second decimal place) to define the contact angle.

[0115] Next, in the nonwoven fabric 10 of the present embodiment, a more preferable embodiment of the above-mentioned concavo-convex structure will be described.

[0116] The wall portion 1B of the first fiber layer M1 preferably has a shape extending perpendicularly to the direction along the plane of the other surface side 10B of the nonwoven fabric 10 (the second fiber layer M2). By making the wall portion 1B have a vertical wall surface, the valley between the root 1D of the wall portion 1B and the raised portion 5 is narrower, and the shadow becomes stronger. In addition, it can be recognized that the shadow emerges from the vertical wall portion 1B. As a result, the visibility of the opening portion 3 is further improved.

[0117] Moreover, the vertical wall portion 1B connects the top 1A and the second fiber layer M2 vertically, further enhancing the aforementioned shadow. In addition, the aforementioned effect brought about by the longitudinal orientation of the fibers is strengthened. That is, the soft fiber layer of the top 1A is likely to remain in a state supported by the elastic fiber layer of the wall portion 1B. The thickness of the fiber layer of the convex portion 1 can be felt through the top 1A, and a softer touch can be easily obtained. More specifically, this soft touch can be felt as a gentle and reassuring thickness under light pressure to the extent of touching, and under further pressure, although the convex portion 1 is deformed, it is not easy to collapse, and can be felt as a soft thickness with elasticity. Such excellent cushioning properties make the skin feel brought about by the aforementioned concave-convex structure even better.

[0118] The "vertical" of the wall 1B does not only refer to Figure 1 The angle θ shown relative to the plane of the other side 10B of the nonwoven fabric 10 (the second fiber layer M2) is strictly 90°, and also refers to the case where it is greater than 60° and less than 120°. By being within this range, the wall portion 1B has a shape extending at an angle substantially considered to be 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 portion 1B. Specifically, as Figure 1 As shown, in the cross section including the thickness direction of the protrusion 1, it means the angle of the inner angle among the angles formed by the center line M of the width of the fiber layer of the wall portion 1B and the straight line L contacting the surface of the other surface side 10B of the nonwoven fabric 10 (the second fiber layer M2). This angle θ can be obtained by observing the microscopic photograph of the cross section obtained using the aforementioned microscope.

[0119] Figure 1 In the example shown, the wall portion 1B extends in a straight line between the top 1A and the second fiber layer M2, and the entire wall portion 1B is vertically erected relative to the second fiber layer M2. However, this is not limited to this, and the wall portion 1B may also be configured to include a portion extending in a curved or wavy shape between the top 1A and the second fiber layer M2. In this case, the line connecting the intersection point of the top 1A and the wall portion 1B and the intersection point of the second fiber layer M2 and the wall portion 1B is set as the above-mentioned center line M, and the above-mentioned angle θ is determined.

[0120] In addition, although it is preferred that all of the multiple wall portions 1B extend perpendicularly to the second fiber layer M2, a wall portion that does not extend perpendicularly to the plane of the other surface side 10B of the second fiber layer M2 may be included in a part of the wall portion 1B. In the latter case, the number of the wall portions 1B in a vertical state is preferably 60% or more of the wall portions 1B present in all the multiple protrusions 1 from the viewpoint of further enhancing the display of the aforementioned shadow in the nonwoven fabric 10 and making the aforementioned effect of the longitudinal orientation of the fibers more efficient.

[0121] Furthermore, in the first fiber layer M1, it is preferred that a hollow region 1C exists on the other surface side 10B of the convex portion 1. The hollow region 1C is a space that is not substantially filled with fibers of the nonwoven fabric 10. Specifically, it means that the fiber density determined by the method described below is less than 10 fibers / mm 2 The fiber density in the hollow region 1C is as small as possible.

[0122] Furthermore, from the viewpoint of improving liquid permeability, it is preferred that the raised portion 5A of the second fiber layer M2 also enters the hollow region 1C of the first fiber layer M1 .

[0123] (Method for determining fiber density)

[0124] 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 portion to be measured (e.g., between the walls 1B). The cut surface is magnified and observed using a scanning electron microscope (JCM-6000Plus (trade name) manufactured by JEOL Ltd.), and the cross sections of the cut fibers within a certain area of ​​the cut surface are counted. During the magnified observation, the magnification is adjusted to be able to measure the cross sections of about 30 to 60 fibers (150 times or more and 500 times or less). Then, the fiber density is converted to 1 mm2 / s. 2 The number of fiber cross-sections in the fiber is set as the fiber density (fibers / mm 2 ). The measurement results at the three locations were averaged and taken as the fiber density of the sample.

[0125] By placing the hollow region 1C on the other side 10B of the convex portion 1, the soft touch of the convex portion 1 is further improved, the aforementioned cushioning properties are further improved, and the skin touch of the nonwoven fabric 10 becomes even better. In addition, when the nonwoven fabric 10 is used as a surface sheet of an absorbent article, the liquid back-seepage path from the absorbent body is cut off due to the interposition of the hollow region 1C, and the liquid back-seepage prevention is improved. Moreover, the hollow region 1C is also a primary storage space when the excretion volume is too large, which can reduce the amount of residual liquid on the skin contacting side of the surface sheet.

[0126] Next, Figure 1 For a specific example of the nonwoven fabric 10 (nonwoven fabric 20), refer to Figures 5 to 8 The nonwoven fabric 20 has the above-described structure described for the nonwoven fabric 10 .

[0127] Figures 5 to 8 The nonwoven fabric 20 shown has, as the projections 1 of the first fiber layer M1 described above, a plurality of ridges 11 extending in one direction Y and arranged apart from each other in a direction X intersecting the one direction Y, in a plan view from one surface side 20T. The other surface side 20B of the ridges 11 is provided as a hollow area 11C.

[0128] The one direction Y and the direction X intersecting the one direction Y can be appropriately set according to the purpose in the surface of the one surface side 20T of the nonwoven fabric 20. For example, it is preferable that the one direction Y and the direction X intersecting the one direction Y are directions orthogonal to each other. When the nonwoven fabric 20 is used as a component such as a surface sheet in an absorbent article, it is preferable that the one direction Y is set as the longitudinal direction of the absorbent article, and the direction X intersecting the one direction Y is set as the width direction of the absorbent article.

[0129] The plurality of ridges 11 have the same height along the extending direction. The term “same height” means that the height measured using a microscope VHX900 (trade name, manufactured by KEYENCE CORPORATION) is within a range of 0.8 to 1.2 times the average value of the measurement.

[0130] Each of the plurality of ridges 11 includes a top portion 11A and a wall portion 11B supporting the top portion 11A. The top portion 11A is a fiber layer that contacts the skin of the wearer in the absorbent article, and the wall portion 11B is a fiber layer that connects the top portion 11A and the second fiber layer M2 in the thickness direction. That is, when the nonwoven fabric 20 is applied to the absorbent article, one surface side 20T becomes the skin contact surface side, and the other surface side 20B becomes the non-skin contact surface side. The fibers of the wall portion 11B are preferably longitudinally oriented as described above. In addition, the shape of the wall portion is preferably extended perpendicularly to the second fiber layer M2, connecting the top portion 11A perpendicularly to the bottom portion 12 provided with the opening portion 3.

[0131] The longitudinal orientation ratio indicating the longitudinal orientation of the fibers of the wall portion 11B can be expressed as Figure 6 As shown, in the cross section orthogonal to the direction in which the ridge portion 11 extends ( Figure 5 The measurement is performed based on the above-mentioned method (the measurement method of the longitudinal orientation ratio of the fibers in the wall portion 1B) in the thickness direction cross section at the position of the R1-R1 line along the width direction X.

[0132] In addition, the verticality of the wall portion 11B is as follows: Figure 6 As shown, it means a cross section perpendicular to the direction in which the ridge portion 11 extends ( Figure 5 θ is the internal angle among the angles formed by the center line M of the width of the fiber layer of the wall portion 11B and the straight line L contacting the surface of the other side 20B of the nonwoven fabric 20 (the second fiber layer M2) at the position of the R1-R1 line in the thickness direction cross section along the direction X intersecting with the one direction Y. The angle θ can be obtained by observing the microscope photograph of the cross section of the R1-R1 line obtained by the aforementioned microscope.

[0133] In the nonwoven fabric 20, as the aforementioned protrusion 1 in the first fiber layer M1, there is the aforementioned ridge portion 11 and a saddle portion 15 connecting the adjacent ridge portions 11, 11. The saddle portion 15 is a three-dimensional fiber layer that protrudes from the second fiber layer M2 to one surface side 20T of the nonwoven fabric 20 in the same manner as the ridge portion 11 and is erected in the thickness direction of the nonwoven fabric 20. More specifically, the saddle portion 15 has a top 15A on one surface side 20T and a wall portion 15B that supports the top 15A. The fibers of the wall portion 15B are preferably longitudinally oriented as described above. In addition, the wall portion 15B preferably extends perpendicularly to the second fiber layer M2. The above-mentioned "vertical" has the same meaning as the "vertical" defined in the aforementioned ridge portion 11.

[0134] The longitudinal orientation ratio indicating the longitudinal orientation of the wall portion 15B in the saddle portion 15 and the “verticality” of the wall portion 15B can be expressed as Figure 7 The cross section ( Figure 5 The thickness direction cross section at the position of the R2-R2 line along one direction Y) is measured in the same manner as the aforementioned measurement method for the wall portion 11B.

[0135] The above structure makes it difficult for the ridges 11 connected by the saddle 15 to approach each other, and the ridges 11 are suppressed from collapsing in one direction due to external forces such as pressing. That is, the saddle 15 supports the ridges 11 from the side, improving the shape retention of the ridges 11. As a result, it is easier to retain the thickness of the ridges 11 under load. For example, when the non-woven fabric 20 is loaded into an absorbent article as a surface sheet, even if there is a body pressure of the wearer when the absorbent article is worn, it is easy to maintain the distance between the top 11A and the absorbent side of the other surface side (non-skin contact surface side) 20B, so that it is more difficult to generate liquid back-seepage to one surface side (skin contact surface side) 20T. In addition, due to the presence of the saddle 15, the excrement is intercepted between the ridges 11, 11, and the liquid flow prevention is improved on one surface side (skin contact surface side) 20T of the non-woven fabric 20.

[0136] The saddle portion 15 extends in a direction X that intersects with a direction Y that the ridge portion 11 extends in a top view from one side 20T of the nonwoven fabric 20. The direction X that the saddle portion 15 extends can be set to various directions as long as it is a direction connecting adjacent ridge portions 11, and is preferably a direction orthogonal to the direction Y that the ridge portion 11 extends. For example, it is preferred that the direction Y that the ridge portion 11 extends is set as the length direction of the absorbent article, and the direction X that the saddle portion 15 extends and intersects with the above-mentioned direction is set as the width direction of the absorbent article. Hereinafter, the direction Y and the direction X orthogonal to the direction Y are also referred to as the extension direction Y of the ridge portion 11 and the extension direction X of the saddle portion 15.

[0137] In addition, the planar shape of each saddle portion 15 viewed from one surface side 20T is as long as Figure 5 The rectangular shape shown may be set to various shapes. For example, the planar shape of the saddle portion 15 viewed from one surface side 20T may be set to gradually increase in width as it approaches the ridge portion 11.

[0138] The saddles 15 are arranged in a plurality of band regions 16 extending parallel to the ridges 11 between the ridges 11, 11 in a plan view of one surface side 20T of the nonwoven fabric 20. In each band region 16, a plurality of saddles 15 are arranged at intervals along the extension direction Y of the parallel ridges 11. The openings 3 of the bottom 12 described above exist in the spaced-apart portions of the saddles 15. That is, in each band region 16, the saddles 15 and the openings 3 are alternately arranged. Thus, the openings 3 are surrounded and divided by the wall portions 11B of the ridges 11 and the wall portions 15B of the saddles 15. More specifically, the region surrounded by the plurality of ridges 11 and the plurality of saddles 15 as a three-dimensional fiber layer arranged upright in the thickness direction becomes a box-shaped or cylindrical recess, and the openings 3 are arranged at its bottom 12.

[0139] Figures 5 to 8In the example shown, in a plan view from one side 20T of the nonwoven fabric 20, the ridges 11 and the saddles 15 are arranged in a lattice, and the openings 3 of the bottom 12 are scattered in the lattice and arranged in a lattice. The raised portions 5 of the second fiber layer M2 enter the lattice-shaped recessed space divided by the wall portions 11B and the wall portions 15B from the openings 3 surrounded by the ridges 11 and the saddles 15. By surrounding the raised portions 5 of the second fiber layer M2 in a lattice by the wall portions 11B and the wall portions 15B, the shadow around the aforementioned openings 3 is further enhanced and displayed, which is preferred. That is, there is a contact area 4 with the second fiber layer M2 on the four walls 11B and 15B surrounding the raised portion 5, and a valley is formed on the four sides between the root 1D of the wall 11B and the wall 15B and the lower edge 7 of the raised portion 5, as well as a shadow caused by the valley, so that the contours of the raised portion 5 and the opening portion 3 can be observed more clearly.

[0140] Although the saddle portion 15 has the same three-dimensional fiber structure as the ridge portion 11, it is preferred that Figure 7 and Figure 8 As shown, there is a portion lower than the ridge portion 11 relative to the bottom 12. Thus, the contact area between the one surface side 20T of the nonwoven fabric 20 and the skin can be reduced, the skin feel is kept good, the air permeability is improved, and the stuffiness between the skin is further suppressed.

[0141] The difference (H3-H4) 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 is preferably 0.5 mm or more and 7 mm or less from the viewpoint of making the above-mentioned effect better. It should be noted that the height H3 of the ridge portion 11 in the thickness direction is the distance in the thickness direction from the plane in contact with the surface of the other side 20B of the nonwoven fabric 20 (the second fiber layer M2) to the one side 20T of the top 11A of the ridge portion 11. The height H4 of the saddle portion 15 in the thickness direction is the distance in the thickness direction from the plane in contact with the surface of the other side 20B of the nonwoven fabric 20 (the second fiber layer M2) to the one side 20T of the lowest position of the top 15A of the saddle portion 15.

[0142] (Method for 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)

[0143] For nonwoven fabric 20 Figure 7 The thickness direction cross section ( Figure 5The second fiber layer M2 is set 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 the top 11A of the ridge portion 11 and the height H4 from the horizontal table to the top 15A of the saddle portion 15 are measured. The height difference (H3-H4) is calculated based on these measured values. The above-mentioned microscope can be used to measure the height relative to the horizontal table.

[0144] In addition, from the viewpoint of further promoting the discharge of liquid to the other surface side 20B of the nonwoven fabric 20 when the nonwoven fabric 20 is used as the surface sheet of the absorbent article, the saddle portion 15 is more preferably as follows: Figure 7 The saddle portion 15 has a hollow area 15C. The definition and measurement method of the hollow area 15C are the same as those of the hollow area 11C in the ridge portion 11. The hollow area 15C of the saddle portion 15 is preferably connected to the hollow area 11C of the ridge portion 11. As a result, the diffusion of the excretion liquid on the other side 20B of the nonwoven fabric 20 is promoted, thereby further suppressing the liquid retention on the one side 20T. As a result, it is easier to reduce the amount of residual liquid in the nonwoven fabric 20, and the amount of liquid adhering to the skin can be further reduced.

[0145] Next, a preferred embodiment of the method for manufacturing the nonwoven fabric 20 is described with reference to Figures 9 to 12 The manufacturing method described below can also be applied to the manufacturing method of the nonwoven fabric 10.

[0146] The manufacturing method of this embodiment is as follows Fig. 9 As shown, there are the following four steps (hereinafter, each step may be referred to as step (I), step (II), step (III), and step (IV).).

[0147] (I) A first fiber web 100 is placed on a support body 120 having a concave-convex shape having a plurality of protrusions 121 and recesses 125 between the protrusions 121 and 121, and the first fiber web 100 is pressed along the recesses 125 using a pressing portion 131 of a pressing member 130, thereby forming a concave-convex open-pore fiber web 101 having an open-pore surface on the side opposite to the support body 120 while shaping the first fiber web 100 and opening the portions corresponding to the protrusions 121.

[0148] (II) After removing the pressing member 130 from the support 120 , the first hot air W1 is blown toward the concavo-convex open-pore fiber web 101 to fuse the fibers together to obtain the concavo-convex open-pore nonwoven fabric 102 .

[0149] (III) A step of supplying the second fiber web 103 and laminating it on the open-pore surface side of the concavo-convex open-pore nonwoven fabric 102 .

[0150] (IV) A heat fusion step of blowing the second hot air W2 to fuse the fibers of the concavo-convex open-pore nonwoven fabric 102 and the second fiber web 103 to each other, and also to fuse the fibers in the second fiber web 103 to each other.

[0151] The first fiber web 100 is a precursor of the first fiber layer M1 in the nonwoven fabric 20 and includes thermoplastic fibers. The second fiber web 103 is a precursor of the second fiber layer M2 in the nonwoven fabric 20 and includes thermoplastic fibers.

[0152] The so-called "fiber web" of the first fiber web 100 and the second fiber web 103 is a fiber assembly in which the constituent fibers including thermoplastic fibers are not fused and fixed but are loosely entangled and do not have the shape retention property as a sheet. In other words, it is a fiber assembly before being made into a non-woven fabric. Therefore, the mobility between the fibers in the fiber web is high, and the deformability of the fiber web in the above-mentioned pressing process is high. Such a first fiber web 100 and the second fiber web 103 are respectively supplied by a carding machine (not shown) in a manner to achieve a predetermined thickness.

[0153] In step (I), if Fig. 9 As shown in (A), the first fiber web 100 on the support 120 is directly pressed with mechanical pressure using a pressing member 130. As a result, a concave-convex open-pore fiber web 101 is formed to become the first fiber layer M1 in the nonwoven fabric 20. Compared with the case of pressing with non-mechanical pressure such as wind, such shaping causes the fibers to be strongly oriented, and an orientation perpendicular to the plane of the nonwoven fabric can be obtained. In addition, in order to increase the concave-convex height difference for shaping the first fiber web 100, it is not necessary to increase the pressing force too much, and the first fiber web 100 can be gently shaped. In addition, the scattering of the fibers can be suppressed and the shaping property can be improved.

[0154] The support body 120 is, for example, Fig. 9 The cylindrical component shown in the figure has, on the circumference of the cylinder, for example, Fig. 9 (A) The protrusion 121 shown. On the cylindrical surface of the support body 120, for example Fig.10 As shown, a plurality of protrusions 121 are arranged at intervals along one direction (first direction D1) and a direction (second direction D2) orthogonal thereto. A plurality of protrusion rows 121A are arranged in the second direction D2, separated from each other. The protrusions 121 have a spire 122 at the front end. The spire 122 forms the opening 3 of the bottom 12 of the first fiber layer M1.

[0155] The planar shape of the protrusion 121 as viewed from one side of the spire portion 122 is not limited to the following. Fig.10 The rectangle shown can be in various shapes, such as a circle, an ellipse, a diamond, etc.

[0156] The recess 125 includes 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.

[0157] In the support body 120, a plurality of protrusions 121 are arranged corresponding to the positions of the openings 3 forming the bottom 12 of the first fiber layer M1 in the nonwoven fabric 20. The second recesses 125C between the protrusions 121, 121 of the protrusion row 121A are located at the positions that shape the saddle 15 of the first fiber layer M1 in the nonwoven fabric 20. That is, the protrusion row 121A is located at the positions that become the band regions 16 between the ridges 11, 11 in the first fiber layer M1 of the nonwoven fabric 20. The first recesses 125A are located at the positions that become the ridges 11 in the first fiber layer M1 of the nonwoven fabric 20.

[0158] The bottom of each recess 125 is structured to allow hot air to pass therethrough, and is provided with, for example, a plurality of holes (not shown).

[0159] The pressing member 130 is, for example, Fig. 9 The roller-shaped component shown has, on the roller circumference, for example, Fig. 9 (A) shows the pressing portion 131. On the roller circumference of the pressing member 130, for example, Fig.11 As shown in FIG. 1 , a plurality of press-fit portions 131 are arranged at intervals along the second direction D2 and are continuous along the first direction D1. A recess 132 is formed between the press-fit portions 131 and 131 and is continuous along the first direction D1.

[0160] The press-fit portion 131 of the press-fit member 130 corresponds to the first recess 125A of the support body 120 . The recess 132 of the press-fit member 130 corresponds to the protrusion row 121A of the support body 120 .

[0161] The bottom of the recessed portion 132 of the press-fit member 130 is structured to allow hot air to pass therethrough, and is provided with, for example, a plurality of holes (not shown).

[0162] The height of the press-fit portion 131 of the press-fit member 130 is preferably 1 mm or more in order to be sufficiently inserted between the protrusions 121 of the support body 120 .

[0163] The first direction D1 and the second direction D2 of the support body 120 and the pressing member 130 are preferably the machine direction (MD) and the width direction (CD) orthogonal to the machine direction in the manufacturing process. The machine direction and the width direction in the manufacturing process preferably correspond to a direction Y of the nonwoven fabric 20 and a direction X crossing the direction Y, and preferably correspond to the length direction and the width direction of the absorbent article including the nonwoven fabric 20. However, the first direction D1 and the second direction D2 are not limited to these directions.

[0164] In step (I), the protrusion 121 of the support body 120 is inserted into the recess 132 of the press member 130. The press member 130 is inserted into the first recess 125A of the support body 120 ( Fig. 9 (A) and Fig.12 ). Using the support body 120 ( Fig.10 ) and the press-fit member 130 ( Fig.11 ) are pressed into each other, which can appropriately form the concave-convex shape of the first fiber layer M1.

[0165] The first fiber web 100 is pressed and shaped by the pressing portion 131 of the pressing member 130 at the position of the first recess 125A of the support body 120. This portion becomes the ridge portion 11 in the first fiber layer M1 of the nonwoven fabric 20. At this time, between the protrusion 121 of the support body 120 and the pressing portion 131 of the pressing member 130, the fibers of the first fiber web 100 are shaped into a shape vertically arranged along the thickness direction. The shaped fibers are highly mobile fibers that do not fuse, and are therefore oriented in the thickness direction. This portion becomes the wall portion 11B of the ridge portion 11 in the first fiber layer M1 of the nonwoven fabric 20.

[0166] Meanwhile, the fibers of the first fiber web 100 are pushed up toward the bottom of the recess 132 of the pressing member 130 at the position of the protrusion 121 of the support body 120 to form holes. This portion becomes the opening 3 of the bottom 12 of the first fiber layer M1 of the nonwoven fabric 20.

[0167] Since the recess 132 of the pressing member 130 corresponds to the second recess 125C between the protrusions 121, 121 in the protrusion row 121A of the support body 120, the pressing portion 131 does not enter. However, the pressing force of the pressing portions 131, 131 of the pressing member 130 acts on both sides of the fibers of the first fiber web 100 located in the second recess 125C of the protrusion row 121A. Due to this action, the fibers of the first fiber web 100 located in the second recess 125C are stretched in the second direction D2 by the pressing portions 131, 131 on both sides and pressed in the thickness direction, and the orientation of the fibers is changed while being shaped in the thickness direction. This portion becomes the saddle portion 15 in the first fiber layer M1 of the nonwoven fabric 20. The saddle portion 15 is a portion having a top portion 15A and a wall portion 15B, and the wall portion 15B is a portion similar to the wall portion 11B of the ridge portion 11.

[0168] It should be noted that the height of the protrusion 121 of the support body 120 and the height of the press-in portion 131 of the press-in member 130 are appropriately determined according to the thickness of the nonwoven fabric to be manufactured, etc. For example, it is preferably 2 mm or more, more preferably 3 mm or more, and further preferably 5 mm or more. In addition, it is preferably 15 mm or less, more preferably 10 mm or less, and further 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 further preferably 5 mm or more and 9 mm or less.

[0169] Then, in step (II), after the pressing member 130 is removed from the support 120, the first hot air W1 is blown toward the concave-convex open-pore fiber web 101 to fuse the fibers together to obtain the concave-convex open-pore nonwoven fabric 102 ( Fig. 9 (B)). The concavo-convex open-pore nonwoven fabric 102 becomes the first fiber layer M1 of the nonwoven fabric 20. For example, after the pressing member 130 inserted into the support body 120 is removed, the concavo-convex open-pore fiber web 101 is rotated while still being kept on the support body 120, and after passing through the bite portion between the support body 120 and the pressing member 130, the fiber web 101 is heated at the position of the hot air blowing unit 140. Fig. 9 (B) Blowing of the first hot air W1 to the concavo-convex open-pore fiber web 101 The support body 120 preferably has a hot air suction unit 141 at a position facing the hot air blowing unit 140 inside the cylinder.

[0170] The temperature of the first hot air W1 is set to a temperature that can melt the thermoplastic fibers constituting the concave-convex open-pore fiber web 101 and form a fiber fusion portion at the intersection of the fibers. Considering the general fiber materials used in such products, it is preferably 0°C or higher and 70°C or lower than the melting point of the thermoplastic fibers constituting the concave-convex open-pore fiber web 101, and more preferably 5°C or higher and 50°C or lower.

[0171] The wind speed of the first hot air W1 is preferably 1 m / s or more, more preferably 2 m / s or more, from the viewpoint of efficient fusing. In addition, the wind speed of the first hot air W1 is preferably 100 m / s or less, more preferably 80 m / s or less, from the viewpoint of making the device compact.

[0172] Then, in step (III), the second fiber web 103 is supplied and laminated on the open hole side of the concavo-convex open hole nonwoven fabric 102 ( Fig. 9 (C)). For example, the concavo-convex open-pore nonwoven fabric 102 formed by blowing the first hot air W1 is separated from the cylindrical peripheral surface of the support body 120, and is transported downstream by a conveyor belt with the side where the opening portion 3 is formed by the protrusions 121 being upward, so that the second fiber web 103 merges and is stacked on the open-pore side thereof.

[0173] Then, in step (IV), the second hot air W2 is blown in the fusing furnace 170 to fuse the fibers of the concavo-convex open-pore nonwoven fabric 102 and the second fiber web 103 to each other, and the fibers in the second fiber web 103 to each other ( Fig. 9 (D)). Thus, the concavo-convex open-pore nonwoven fabric 102 and the second fiber web 103 are integrated and the second fiber web 103 is transformed into a nonwoven fabric. The nonwoven fabric of the second fiber web 103 becomes the second fiber layer M2 of the nonwoven fabric 20.

[0174] At this time, if Fig. 9 As shown in (D), the concavo-convex open-pore nonwoven fabric 102 is placed on the net 180 with the side facing downward, and the second hot air W2 is blown from one side of the second fiber web 103, thereby pressing the second fiber web 103 in. The pressed-in second fiber web 103 enters the area divided by the wall portion 11B and the wall portion 15B from the opening portion 3 of the concavo-convex open-pore nonwoven fabric 102, forming a raised portion 5. At the same time, the wall portion 11B and the wall portion 15B in the concavo-convex open-pore nonwoven fabric 102 form a fiber fusion portion located at the intersection of the fibers with the second fiber web 103 in the contact area with the second fiber web 103 and are integrated. In addition, the wall portion 11B and the wall portion 15B are embedded in the second fiber web 103. Since this embedding is caused by the second hot air W2, it is performed while maintaining the shape of the wall portion 11B and the wall portion 15B. Moreover, due to the blowing treatment of the second hot air W2, the shape (height) of the wall portion 11B and the wall portion 15B is easily maintained, and the wall portion 11B and the wall portion 15B are closely fitted and integrated with the second fiber web 103 in the maintained state. In this way, the second fiber layer M2 (the nonwoven fiber layer of the second fiber web 103) is closely fitted on the entire surface (wall portion 11B, wall portion 15B and opening portion 3) of the concavo-convex open-pore nonwoven fabric 102 (first fiber layer M1) and integrated, thereby obtaining the aforementioned nonwoven fabric 20.

[0175] For example Fig.13(A) cross section (equivalent to Figure 6 As shown in the cross section at the position of the first fiber layer M1 and the second fiber layer M2, the undulating shapes in the thickness direction are synchronized, so that they can be formed as a material that is fully bonded. Even if the whole surface is bonded, the three-dimensional shape of the wall portion 1B is fully maintained. At the same time, as shown in FIG. Fig.14 As shown, in the above-mentioned close contact state, the protrusions 5 of the second fiber layer M2 enter the area partitioned by the wall portion 11B from the openings 3 of the first fiber layer M1.

[0176] On the other hand, in a conventional manufacturing method different from the above, for example, in 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 stacked and subjected to hot air treatment, even if the same Fig.13 (A) The same conditions as the treatment using the second hot air W2, Fig.13 (B) cross section (equivalent to Figure 6 The cross section of the location) and Fig.15 As shown, the second fiber layer M2 does not enter the opening 3. In addition, the two layers are separated in this part to form a gap, and the shadow around the opening 3 is not enhanced. In addition, in a manufacturing method different from the conventional example, for example, a manufacturing method in which the first fiber layer M1 and the second fiber layer M2 that have been pre-formed into non-woven fabrics are integrated using a hot melt adhesive or the like, it is necessary to destroy the lower part of the wall 11B to ensure the bonding surface, and it is difficult to maintain the shape of the wall 11B.

[0177] Therefore, the nonwoven fabric of the present invention can be suitably produced by the method for producing a nonwoven fabric of the present embodiment including the above-described step (I), step (II), step (III), and step (IV).

[0178] Regarding the temperature of the second hot air W2, considering the general fiber materials used in this type of product, it is preferably 0°C or higher and 70°C or lower than the melting point of the thermoplastic fibers constituting the concave-convex open-pore non-woven fabric 102 and the second fiber mesh 103, and more preferably 5°C or higher and 50°C or lower.

[0179] 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 fiber web 103 with each other and fixing the concavo-convex open-pore nonwoven fabric 102 and the second fiber web 103 with sufficient strength. In addition, the wind speed of the second hot air W2 is preferably 50 m / s or less, and more preferably 30 m / s or less, from the viewpoint of further improving the softness of the nonwoven fabric 20.

[0180] It should be noted that in the above manufacturing method, the press-in component 130 is not limited to Fig.11The member shown has continuous press-in parts 131 in the first direction D1. For example, the press-in parts 131 may be made into a grid shape, and the grid-shaped press-in parts 131 may be provided with measuring bucket-shaped recessed parts 132. In this case, the height of the shaped saddle part 15 becomes higher, and the concavity and convexity become more clear.

[0181] In the method for producing a nonwoven fabric of the present embodiment, it is preferred that a cooling step be provided after blowing the first hot air W1. Fig. 9 As shown, at a position where the concavo-convex open-pore nonwoven fabric 102 obtained by blowing the first hot air W1 is arranged along the outer circumference of the cylinder of the support body 120, the cooling unit 160 having a cooling nozzle and the cooling suction unit 161 inside the cylinder of the support body 120 are arranged facing each other. In this way, the support body 120 can be controlled to be below a certain temperature, so that the obtained nonwoven fabric can be peeled off while maintaining its shape. As a result, in the manufactured nonwoven fabric 20, the shape of the wall portion 11B and the wall portion 15B of the first fiber layer M1 can be well maintained, so that it has good cushioning properties and the visibility of the open-pore portion 3 is more excellent.

[0182] As the thermoplastic fiber constituting the nonwoven fabric of the present invention, fibers commonly used as raw materials for nonwoven fabrics can be adopted without particular limitation. For example, fibers containing a single resin component, composite fibers containing multiple resin components, etc. Composite fibers, for example, have a core-sheath structure, a side-by-side structure, etc.

[0183] When a composite fiber containing a low melting point component and a high melting point component (e.g., a composite fiber of a core-sheath structure in which the sheath is a low melting point component and the core is a high melting point component) is used as a thermoplastic fiber, the temperature of the hot air blown to the fiber web in the manufacturing process is preferably above the melting point of the low melting point component and lower than the melting point of the high melting point component. It is more preferably a temperature above the melting point of the low melting point component and 10°C lower than the melting point of the high melting point component, and it is further preferably a temperature that is 5°C higher than the melting point of the low melting point component and 20°C lower than the melting point of the high melting point component. In addition, from the perspective of elasticity, in a composite fiber of a core-sheath structure, the more cores are high melting point components, the higher the elasticity. Therefore, it is preferred that the core component is larger in terms of cross-sectional area ratio. As a specific example of a composite fiber of a core-sheath structure in which the sheath is a low melting point component and the core is a high melting point component, a composite fiber of 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) can be cited.

[0184] In addition, in the composite fiber with a core-sheath structure, when the glass transition temperature of the sheath resin component is lower than that of the core resin component (hereinafter referred to as the low glass transition temperature resin component. For example, the core resin component is PET and the sheath resin component is PE), the thickness recovery of the non-woven fabric can be further improved by reducing the mass ratio of the low glass transition temperature resin component.

[0185] The nonwoven fabric of the present invention can be used for various purposes. For example, it can be used as a component of various absorbent articles. The above-mentioned various absorbent articles widely include articles for absorbing liquid discharged from the body, such as diapers for adults and infants, sanitary napkins, panty liners for women, urine-absorbing pads, etc.

[0186] The absorbent article having the nonwoven fabric of the present invention typically comprises a top sheet, a back sheet, and a liquid-retaining absorber sandwiched between the two sheets. In the above-mentioned absorbent article, the nonwoven fabric of the present invention can be preferably used as a top sheet that contacts the skin of the wearer.

[0187] Regarding the above-mentioned embodiment, the present invention further discloses the following nonwoven fabric and method for producing the nonwoven fabric.

[0188] <1> A nonwoven fabric for an absorbent article,

[0189] The invention has a first fiber layer and a second fiber layer stacked in the thickness direction, and includes a fiber fusion portion located at a cross section between the fibers.

[0190] The first fiber layer has a concave-convex structure including a plurality of convex portions and a bottom portion provided between adjacent convex portions, each of the plurality of convex portions includes a top portion and a wall portion supporting the top portion, and an opening portion penetrating in the thickness direction is arranged at the bottom portion.

[0191] The second fiber layer is provided on the side of the first fiber layer having the bottom portion,

[0192] The second fiber layer has a protruding portion on a surface facing the first fiber layer, the protruding portion extending from the opening portion of the first fiber layer into a region partitioned by the wall portion.

[0193] <2>

[0194] The nonwoven fabric for an absorbent article according to the above <1>, wherein the protrusions are visible from the first fiber layer side.

[0195] <3>

[0196] The nonwoven fabric for absorbent articles according to <1> or <2>, wherein the surface of the second fiber layer facing the first fiber layer is a continuous fiber layer extending in a planar direction.

[0197] <4>

[0198] The nonwoven fabric for absorbent articles according to any one of <1> to <3>, wherein the nonwoven fabric has a fiber fusion portion located at an intersection of fibers of the wall portion and fibers of the second fiber layer in a contact region between the wall portion of the first fiber layer and the second fiber layer.

[0199] <5>

[0200] The nonwoven fabric for absorbent articles according to any one of <1> to <4>, wherein the lower edge of the protrusion is connected to a contact region between the wall portion of the first fiber layer and the second fiber layer.

[0201] <6>

[0202] A nonwoven fabric for absorbent articles according to any one of items <1> to <5>, wherein in the contact area between the wall portion in the first fiber layer and the second fiber layer, the fibers of the second fiber layer are oriented in a planar direction, and the fibers on the surface of the lower edge portion of the raised portion have a fiber orientation different from that of the fibers of the wall portion.

[0203] <7>

[0204] The nonwoven fabric for an absorbent article according to any one of <1> to <6>, wherein the top portion has a flat surface.

[0205] <8>

[0206] The nonwoven fabric for absorbent articles according to any one of <1> to <7>, wherein the area of ​​the opening is 1.0 mm 2 Above and 50mm 2 Below, preferably 1.5mm 2 More preferably 2.0 mm 2 Above, preferably 40 mm 2 Below, more preferably 35mm 2 the following.

[0207] <9>

[0208] The nonwoven fabric for absorbent articles according to any one of <1> to <8>, which has a valley formed by a base of the wall portion constituting the convex portion and a lower edge of the raised portion extending toward the base.

[0209] <10>

[0210] According to the nonwoven fabric for an absorbent article according to the above <9>, the lower edge portion is connected to a contact region between the wall portion of the first fiber layer and the second fiber layer.

[0211] <11>

[0212] The nonwoven fabric for an absorbent article according to <9> or <10>, wherein in a region where a root of the wall portion contacts the second fiber layer, the root is embedded in the second fiber layer and integrated therewith.

[0213] <12>

[0214] The nonwoven fabric for absorbent articles according to any one of <1> to <11>, 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, preferably 0.10 or more, more preferably 0.15 or more, and preferably 0.8 or less, more preferably 0.7 or less.

[0215] <13>

[0216] The nonwoven fabric for absorbent articles according to any one of items <1> to <12>, wherein the ratio (D2 / D1) of the fiber diameter (D2) of the fibers of the second fiber layer M2 to the fiber diameter (D1) of the fibers of the first fiber layer is greater than 1.2 and less than 10.0, preferably greater than 1.5, more preferably greater than 2.0, and preferably less than 9.0, more preferably less than 8.0.

[0217] <14>

[0218] The nonwoven fabric for an absorbent article according to any one of <1> to <13>, wherein in the first fiber layer, a hollow region 1C exists on the back side of the convex portion.

[0219] <15>

[0220] The nonwoven fabric for absorbent articles according to any one of <1> to <14>, wherein the basis weight is 20 g / m 2 Above and 100g / m 2 the following.

[0221] <16>

[0222] The nonwoven fabric for absorbent articles according to any one of <1> to <15>, wherein 4.9 mN / cm 2 The thickness under load is 0.8 mm or more and 10 mm or less.

[0223] <17>

[0224] The nonwoven fabric for an absorbent article according to any one of <1> to <16>, wherein fibers of the wall portion are longitudinally oriented.

[0225] <18>

[0226] The nonwoven fabric for an absorbent article according to the above <17>, wherein the longitudinal orientation ratio of the fibers in the wall portion is 60% or more.

[0227] <19>

[0228] The nonwoven fabric for an absorbent article according to any one of <5> to <18>, wherein the longitudinal orientation ratio of fibers on the surface of the lower edge portion is less than 45%.

[0229] <20>

[0230] The nonwoven fabric for an absorbent article according to the above <19>, wherein the difference in longitudinal orientation ratio between the fibers on the surface of the lower edge portion and the fibers in the wall portion is 15% or more.

[0231] <21>

[0232] A nonwoven fabric for absorbent articles according to any one of items <1> to <20>, wherein the convex portion as the first fiber layer has a plurality of ridges and a saddle portion connecting adjacent ridges in a plan view from one surface side, and the plurality of ridges extend in a direction Y and are arranged separately from each other in a direction X intersecting the direction Y.

[0233] <22>

[0234] According to the nonwoven fabric for an absorbent article according to the above <21>, the saddle portion includes a top portion on one surface side and a wall portion supporting the top portion.

[0235] <23>

[0236] The nonwoven fabric for absorbent articles according to any one of <1> to <22>, wherein the fibers constituting the second fiber layer have a smaller fiber diameter than the fibers constituting the first fiber layer.

[0237] <24>

[0238] According to the nonwoven fabric for absorbent articles according to <23>, the difference between the fiber diameter of the constituent fibers of the second fiber layer and the fiber diameter of the constituent fibers of the first fiber layer is 2 μm or more, preferably 3 μm or more, and more preferably 4 μm or more.

[0239] <25>

[0240] According to the nonwoven fabric for absorbent articles described in <23> or <24>, the difference between the fiber diameter of the constituent fibers of the second fiber layer and the fiber diameter of the constituent fibers of the first fiber layer is 50 μm or less, preferably 40 μm or less, and more preferably 30 μm or less.

[0241] <26>

[0242] The nonwoven fabric for absorbent articles according to any one of <1> to <25>, wherein the hydrophilicity of the constituent fibers of the second fiber layer is higher than the hydrophilicity of the constituent fibers of the first fiber layer.

[0243] <27>

[0244] According to the nonwoven fabric for absorbent articles described in the above-mentioned <26>, the difference (G1-G2) between the contact angle (G1) of the constituent fibers of the above-mentioned first fiber layer and the contact angle (G2) of the constituent fibers of the above-mentioned second fiber layer is greater than 0.5 and less than 50.0, preferably greater than 1.0, more preferably greater than 2.0, and preferably less than 45.0, more preferably less than 40.0.

[0245] <28>

[0246] The nonwoven fabric for absorbent articles according to any one of <1> to <27>, wherein the number of fibers per unit area of ​​the second fiber layer is larger than the number of fibers per unit area of ​​the top portion of the first fiber layer.

[0247] <29>

[0248] According to the nonwoven fabric for absorbent articles described in the above-mentioned <28>, the difference between the number of fibers per unit area of ​​the above-mentioned second fiber layer and the number of fibers per unit area of ​​the above-mentioned top in the above-mentioned first fiber layer is greater than 5 and less than 190, preferably greater than 8, more preferably greater than 10, and preferably less than 185, more preferably less than 180.

[0249] <30>

[0250] An absorbent article comprising the nonwoven fabric for absorbent articles according to any one of <1> to <29>.

[0251] <31>

[0252] A method for producing a nonwoven fabric for an absorbent article, the method comprising:

[0253] A pressing step of placing a first fiber web on a support having a concavo-convex shape with a plurality of protrusions and concave portions between the protrusions, pressing the first fiber web along the concave portions using a pressing portion of a pressing member to shape the first fiber web, and opening holes at locations corresponding to the protrusions to form a concavo-convex open-pore fiber web having an open-pore surface on a side opposite to the support;

[0254] After removing the pressing member from the support, blowing a first hot air to the concave-convex open-pore fiber web to fuse the fibers to obtain a concave-convex open-pore nonwoven fabric;

[0255] A step of supplying a second fiber web and laminating it on the open hole side of the concavo-convex open hole nonwoven fabric; and

[0256] A heat fusion step of blowing a second hot air to fuse the fibers of the concavoconvex nonwoven fabric and the second fiber web to each other, and to fuse the fibers in the second fiber web to each other.

[0257] Example

[0258] Hereinafter, the present invention will be described in further detail based on the examples, but the present invention is not to be construed as being limited thereto. It should be noted that, in the present examples, "parts" and "%" are all based on mass unless otherwise specified. "←" means having the same value as the column on the left.

[0259] <Example 1, Comparative Examples 1 and 2>

[0260] [Example 1]

[0261] based on Fig. 9 The manufacturing method shown in the figure implements the following steps to produce Figures 5 to 8 The nonwoven fabric shown was used as a nonwoven fabric sample of Example 1.

[0262] The first fiber web 100 is produced using a core-sheath type (polyethylene terephthalate (PET) / polyethylene (PE) = 5:5) thermoplastic fiber with a fineness of 1.3 dtex. The thermoplastic fiber is subjected to a hydrophilization treatment. The first fiber web 100 is arranged on a support body 120, and a pressing member 130 is pressed into the support body 120 from the first fiber web 100 to perform a shaping treatment. The first hot air W1 is blown to perform a fusion treatment to produce a concave-convex open-pore nonwoven fabric 102 (first fiber layer M1). The first hot air W1 is set to a temperature of 160°C and a wind speed of 20 m / sec. The basis weight of the produced concave-convex open-pore nonwoven fabric 102 is 30 g / m 2 .

[0263] Then, a second fiber web 103 made of core-sheath type thermoplastic fiber with a fineness of 7.8 dtex was laminated on the open hole side of the above-mentioned concave-convex open hole nonwoven fabric 102, and a second hot air W2 was blown to perform a fusion treatment, thereby producing a laminated nonwoven fabric, which was set as the nonwoven fabric sample of Example 1. The second hot air W2 was set to a temperature of 160° C. and a wind speed of 2.0 m / sec.

[0264] The basis weight of the nonwoven fabric sample of Example 1 is 70 g / m 2 In the nonwoven fabric sample of Example 1, the fibers of the wall portions 11B and 15B of the first fiber layer M1 are oriented in the longitudinal direction. The second fiber layer M2 includes the raised portions 5 extending from the openings 3 into the regions defined by the wall portions 11B and 15B.

[0265] [Comparative Example 1]

[0266] A laminated nonwoven fabric was prepared as a nonwoven fabric sample of Comparative Example 1 in the same manner as in Example 1 except that the protrusions 121 in the support were protrusions having planar tips without the perforated portions 122 .

[0267] The nonwoven fabric sample of Comparative Example 1 does not have the openings 3 in the first fiber layer M1 , and does not have the protrusions 5 where the second fiber layer M2 enters the first fiber layer M1 .

[0268] [Comparative Example 2]

[0269] A nonwoven fabric sample of Comparative Example 2 was prepared in the same manner as in Example 1 except that the second fiber web 103 was not laminated and the nonwoven fabric 102 (first fiber layer M1) with concavo-convex open holes was used alone.

[0270] The structures of the nonwoven fabric samples of the examples and comparative examples were studied. Specifically, the basis weight, thickness, angles of the walls 11 and 15 (angles formed between the extending directions of the walls 11 and 15 and the plane of the other surface side 10B of the nonwoven fabric sample), and longitudinal orientation ratios of the walls 11, 15, and the second fiber layer were measured using the following method.

[0271] <Basis weight>

[0272] The area and mass of the nonwoven fabric stored in an environment of 23±2°C and a relative humidity of 50±5% for more than 24 hours were measured and determined.

[0273] <Thickness>

[0274] When 4.9mN / cm is applied to the nonwoven fabric 2 (0.05gf / cm 2The thickness was measured by a thickness measuring instrument under a load of 1000 mm / s. A laser displacement meter manufactured by OMRON Corporation was used as the thickness measuring instrument. The thickness was measured at 10 points, and the average value thereof was calculated as the thickness.

[0275] <Angle of Wall 11 and Wall 15>

[0276] According to the above-mentioned method (method for measuring the longitudinal orientation ratio of fibers in the wall portion 1B), a fiber layer cross section of the wall portion 11 and the wall portion 15 is prepared and a microscope photograph is taken to determine the angle θ formed by the extending direction of the wall portion 11 and the wall portion 15 and the plane of the other surface side 10B of the nonwoven fabric sample.

[0277] <Longitudinal Orientation Ratio of Wall Section 11, Wall Section 15 and Second Fiber Layer>

[0278] The longitudinal orientation ratios of the wall portion 11 , the wall portion 15 , and the second fiber layer are determined based on the above-described method (the method for measuring the longitudinal orientation ratio of the fibers in the wall portion 1B).

[0279] Next, the clarity of the openings (visibility of the openings), liquid absorption time, liquid flow distance, and liquid rewet amount were measured for the nonwoven fabric samples of Example 1 and Comparative Examples 1 and 2. The measurement methods are described below.

[0280] <Clearance of openings>

[0281] The surface sheet was removed from a commercially available baby diaper (trade name "Merries Sarasara Hot Air S", Kao Corporation, manufactured in 2020), and the nonwoven fabric cut out of each nonwoven fabric sample of the embodiment and the comparative example was used as the absorbent core. The nonwoven fabric was stacked with the second fiber layer side facing the absorbent core side, and the periphery of the stacked nonwoven fabric was fixed to produce a diaper for evaluation. Regarding the evaluation of the clarity of the opening portion, three researchers (20s to 30s) engaged in the research and development of nonwoven fabrics conducted a sensory evaluation of whether a clear opening portion was formed in the nonwoven fabric (surface sheet) in 5 levels, and the average value was sorted out. The diaper for evaluation was left to stand, and the nonwoven fabric was visually observed from above, thereby performing a sensory evaluation. Here, if the average value is 3.5 points or more, preferably 4.0 points or more, it is judged that the ridge 5 can be observed from one side of the first fiber layer M1.

[0282] (Sensory Evaluation Criteria)

[0283] 5: The impression of a clear opening portion formed in the concave portion of the entire surface sheet is obtained

[0284] 4: The impression is obtained that clear openings and unclear openings are mixed in the recessed parts throughout the surface sheet.

[0285] 3: The impression of unclear openings formed in the entire surface sheet is obtained

[0286] 2: The impression is obtained that the opening portion is not clearly formed in a part of the concave portion of the surface sheet, and the opening portion is not formed in most of the concave portion.

[0287] 1: The impression is obtained that there is no opening portion formed in the concave portion of the surface sheet

[0288] <Liquid absorption time>

[0289] Diapers for evaluation were prepared in the same manner as in the above <Clearance of the Openings>. A pressure of 13.6 g / cm 2 The pressure load is passed through a tube (cross-sectional area 1017mm) set approximately in the center of the nonwoven fabric. 2 ) Artificial urine (composition: 1.940 mass % urea, 0.795 mass % sodium chloride, 0.110 mass % magnesium sulfate, 0.062 mass % calcium chloride, 0.197 mass % potassium sulfate, 0.010 mass % red No. 2 (dye), water (96.886 mass %)) was injected. 30 g of artificial urine was injected three times every 10 minutes, and the time (seconds) until the entire amount was absorbed was measured. The moment when no artificial urine was confirmed inside the cylinder was defined as "the entire amount was absorbed". The above operation was performed three times, and the average value of the three times was defined as the absorption time (seconds) of the liquid. The shorter the absorption time of the liquid, the easier it is for the liquid to penetrate into the interior. That is, the liquid introduction property is excellent.

[0290] <Liquid flow distance>

[0291] From each nonwoven fabric sample of the embodiment and the comparative example, a 10 cm × 20 cm sample was cut out as an evaluation sample, and fixed on a loading portion inclined at 45 degrees with a commercially available paper towel sandwiched therebetween. 2 g of artificial urine was injected from a height of 10 mm above the evaluation sample in 20 seconds, and the flow of the artificial urine was observed. The distance from the injection point on the vertical line to the place where the artificial urine was introduced into the evaluation sample was measured and set as the liquid flow distance. The above operation was performed 3 times, and the average value of the 3 times was set as the liquid flow distance (mm). The shorter the liquid flow distance, the easier it is for the liquid to penetrate into the interior. That is, the liquid introduction is excellent.

[0292] <Liquid backflow amount>

[0293] The diaper for evaluation was prepared in the same manner as in the above <Clearance of the Opening>. 30 g of colored artificial urine was injected for 10 seconds at a position 165 mm from the ventral end edge in the length direction of the absorbent article and corresponding to the center in the width direction. 30 g was injected again 10 minutes after the start of the injection. 30 g was injected again 10 minutes after the start of the second injection, 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 used was room temperature (20±5°C).

[0294] 10 minutes after the injection, 10 sheets of filter paper No. 4A (100 mm × 100 mm, mass W1) manufactured by ADVANTEC were stacked and placed on the nonwoven fabric with the injection point as the center. An acrylic plate with a thickness of 5 mm and a size of 100 mm × 100 mm was sandwiched, and a pressure of 3.5 kPa was applied. After 2 minutes, the mass (W2) of the filter paper was measured, and the liquid re-permeation amount was calculated as shown in the following formula (I).

[0295] Liquid back permeation (mg) = mass of filter paper after pressurization (W2) - initial mass of filter paper (W1)

[0296] The operation was performed three or more times, and the average value of the three times was defined as the liquid rewetting amount (mg). The smaller the liquid rewetting amount, the less likely liquid rewetting occurs, and the higher the evaluation.

[0297] [Table 1]

[0298]

[0299] As shown in Table 1, the nonwoven fabric sample of Example 1 had an evaluation value of "opening clarity" three times higher than that of the nonwoven fabric samples of Comparative Examples 1 and 2, and the visibility of the openings arranged at the bottom of the concavo-convex structure was improved.

[0300] Furthermore, the nonwoven fabric sample of Example 1 has a shorter "liquid absorption time", a shorter "liquid flow distance", and a smaller "liquid rewet amount" than the nonwoven fabric samples of Comparative Examples 1 and 2, thereby improving liquid absorbency.

[0301] As described above, the nonwoven fabric sample of Example 1 has higher visibility of the openings, which indicates the strength of liquid absorbency required by users, than the nonwoven fabric samples of Comparative Examples 1 and 2, and is superior in actual liquid absorbency.

[0302] <Examples 2 to 4, Comparative Examples 3 to 5>

[0303] (Example 2)

[0304] based on Fig. 9 The manufacturing method shown is made under the following conditions Figures 5 to 8The nonwoven fabric shown was used as a nonwoven fabric sample of Example 2.

[0305] The first fiber web 100 was made of core-sheath type (polyethylene terephthalate (PET) (core): polyethylene (PE) (sheath) = 5:5 (mass ratio)) thermoplastic fibers with a fiber diameter of 14 μm and a basis weight of 30 g / m 2 The second fiber web 103 was made of a core-sheath type (polyethylene terephthalate (PET) (core): polyethylene (PE) (sheath) = 5:5 (mass ratio)) thermoplastic fiber with a fiber diameter of 12 μm and a basis weight of 40 g / m 2 Fiber web.

[0306] In the support body 120, the MD spacing of the protrusion 121 including the spire portion 122 in the top view is set to 5 mm, the CD spacing is set to 5 mm, and the height of the protrusion including the spire portion 122 is set to 3.5 mm. The planar shape of the protrusion 121 observed from the side of the spire portion 122 is set to a square. The CD spacing of the pressing portion 131 of the pressing member 130 is set to 5 mm, and the height of the pressing portion is set to 6 mm. The temperature of the first hot air W1 is set to 160°C, and the wind speed is set to 3.0 m / sec. Thus, the concave-convex open-pore nonwoven fabric 102 (first fiber layer M1) having an open hole portion 3 with a hole area shown in Table 2 is produced.

[0307] The temperature of the second hot air blown to the nonwoven fabric having the second fiber web 103 stacked on the open hole side of the concavo-convex open hole nonwoven fabric 102 was set to 160°C and the wind speed was set to 1.3 m / sec. Figures 5 to 8 The nonwoven fabric sample of Example 2 has the shape shown.

[0308] In the nonwoven fabric sample of Example 2, the walls 11B and 15B of the first fiber layer M1 extend vertically, and the fibers are oriented longitudinally. The constituent fibers of the second fiber layer M2 are shown in Table 2. Compared with the constituent fibers of the first fiber layer M1, the fiber diameter is smaller, and the fibers are exposed to the first fiber layer side in the opening 3. The difference in fiber diameter of the constituent fibers between the first fiber layer M1 and the second fiber layer M2, the difference in the number of fibers per unit area, and the hydrophilicity of the constituent fibers are shown in Table 2. The second fiber layer M2 has a protrusion 5 that enters from the opening 3 into the area divided by the walls 11B and 15B. In addition, the nonwoven fabric sample of Example 2 has a hydrophilicity of 4.9 mN / cm 2 (0.05gf / cm 2 ) The thickness under load is 6.0 mm.

[0309] (Example 3)

[0310] A nonwoven fabric sample of Example 3 was prepared in the same manner as in Example 2 except that the fiber diameters of the constituent fibers of the first fiber web 100 and the second fiber web 103 were set to the values ​​shown in Table 2.

[0311] (Example 4)

[0312] A nonwoven fabric sample of Example 4 was prepared in the same manner as in Example 2 except that the fiber diameters of the constituent fibers of the first fiber web 100 and the second fiber web 103 were set to the values ​​shown in Table 2.

[0313] (Comparative Example 3)

[0314] A nonwoven fabric having a two-layer structure described in Example 1 of Patent Document 2 was prepared as a nonwoven fabric sample of Comparative Example 3. At this time, the first fiber layer M1 as the outer fiber layer on the first surface side and the second fiber layer M2 as the outer fiber layer on the second surface side were each configured as shown in Table 2. The nonwoven fabric sample of Comparative Example 3 did not have an opening 3 in the first fiber layer M1.

[0315] (Comparative Example 4)

[0316] A nonwoven fabric having a single layer structure as described in Example 1 of Patent Document 1 was prepared, and a hot melt adhesive was applied in a spiral shape on the opening side of the nonwoven fabric to join the flat nonwoven fabric. The adhesive coating weight was set to 12 g / m 2 The configurations of the nonwoven fabric of the one-layer structure and the flat nonwoven fabric were as shown in the items of the first fiber layer M1 and the second fiber layer M2 in Table 2, respectively.

[0317] (Comparative Example 5)

[0318] The convex nonwoven fabric used in the surface material of Merries S (Kao Corporation, manufactured in 2021) was peeled off, and a hot melt adhesive was applied in a spiral shape on the non-skin surface of the convex nonwoven fabric to join the flat nonwoven fabric. The adhesive coating weight was set to 12 g / m 2 The structures of the uneven nonwoven fabric and the flat nonwoven fabric were as shown in the items of the first fiber layer M1 and the second fiber layer M2 in Table 2.

[0319] The following tests (1) to (3) were performed using the nonwoven fabric samples of Examples 2 to 4 and Comparative Examples 3 to 5.

[0320] (1) Compression deformation

[0321] Using KES-FB3 (trade name) manufactured by KATO Tech Co., Ltd., the speed of the terminal was set to 0.1 mm / s, and all other compression characteristics were evaluated up to 5.0 kPa in the normal mode. Afterwards, the amount of deformation from 0.15 kP to 2.5 kPa was set as the "compression deformation amount" of each non-woven fabric sample. Based on the "compression deformation amount", the elasticity and cushioning characteristics are determined. The larger the value, the more difficult it is to be flattened in the compression direction due to a small load, and similarly, it has moderate elasticity. In addition, the larger the value, the easier it is to be flattened during the period up to a load of 2.5 kPa. If the value is large, it will deform greatly when touched, so it means that the cushioning characteristics are easy to feel.

[0322] (2) Visualization

[0323] Evaluation was performed based on the method of <Clearance of Opening Portion> described above.

[0324] (3) Liquid absorbency

[0325] (1-1) Preparation of simulated soft stool

[0326] Simulated soft stool was prepared as follows: bentonite (manufactured by Kanto Chemical Co., Ltd., product number: 04066-01, specification: Deer Grade 1), POIZ 530 (manufactured by Kao Corporation), EMULGEN 130K (manufactured by Kao Corporation), and ion-exchanged water were stirred using a digital mixer at a component ratio of 15%, 0.3%, 1.7%, and 83%, respectively, to a viscosity of 40 cP (B-type viscometer: manufactured by Toki Sangyo Co., Ltd., TVB-10M).

[0327] (1-2) Test on the absorption rate of soft stool using simulated soft stool

[0328] Each nonwoven fabric sample of Examples 2 to 4 and Comparative Examples 3 to 5 was placed on an absorbent body with the surface material peeled off of Merries S (Kao Corporation, manufactured in 2021) as a diaper sample. Each diaper sample was spread out in a flat state, and 10 g of simulated soft feces was injected at a flow rate of 6 g / s at a position 30 mm behind the center of each diaper sample in the longitudinal direction. The time for complete absorption of the simulated soft feces (the time until the soft feces penetrates the surface of the diaper and the surface material is exposed) was measured and set as the soft feces absorption rate. The measurement was performed three times, and the average value was set as the soft feces absorption rate.

[0329] (1-3) Surface soft stool flow test using simulated soft stool

[0330] Each diaper sample was spread out in an unfolded state on the inclined surface of an inclined table with an inclined surface angle of 20 degrees, and 10 g of simulated soft feces (viscosity 40 mPa·s) was injected at a flow rate of 6 g / s from a position 30 mm behind the center of each diaper sample relative to the length direction Y and 10 mm above the surface sheet.

[0331] After 30 seconds, the distance that the simulated soft stool on the surface sheet flows from the injection point is measured and is defined as the soft stool flow distance. The measurement is performed three times and the average value is defined as the soft stool flow distance.

[0332] (1-4) Soft stool diffusion area test using simulated soft stool

[0333] After the same test as (1-3), the simulated soft stool spreading area on the surface sheet was transferred to the OHP sheet, scanned and imported into Image-Pro to calculate the soft stool spreading area. The measurement was performed three times, and the average value was set as the soft stool spreading area.

[0334] [Table 2]

[0335]

[0336] As shown in Table 2, the nonwoven fabric samples of Examples 2 to 4 have a larger compression deformation and excellent cushioning properties than the nonwoven fabric samples of Comparative Examples 3 to 5. At the same time, the nonwoven fabric samples of Examples 2 to 4 have a shorter soft stool absorption time, a shorter soft stool flow distance, and a smaller soft stool diffusion area than the nonwoven fabric samples of Comparative Examples 3 to 5, which inhibits the expansion of the liquid and achieves rapid absorption, showing excellent liquid absorbency. Moreover, the nonwoven fabric samples of Examples 2 to 4 have a higher visibility of the opening 3 than the nonwoven fabric samples of Comparative Examples 3 to 5, making it easy for users to recognize the good liquid absorbency through the opening 3.

[0337] Although the present invention has been described together with its embodiments and examples, unless otherwise specified, there is no intention to limit our invention to any details of the description, and it is considered that it should be broadly interpreted without violating the spirit and scope of the invention as shown in the scope of the attached claims.

[0338] This application claims priority based on patent applications No. 2022-151985 filed in Japan on September 22, 2022, and No. 2022-151986 filed in Japan on September 22, 2022, the contents of which are incorporated herein by reference as part of the description of this specification.

[0339] Description of Reference Numerals

[0340] M1: 1st fiber layer; M2: 2nd fiber layer; 1: convex part; 1A: top; 1B: wall; 1C: hollow area; 1D: root; 2: bottom; 3: opening part; 5: raised part; 10, 20: non-woven fabric; 10T, 20T: one surface side; 10B, 20B: the other surface side.

Claims

1. A nonwoven fabric for an absorbent article, The invention has a first fiber layer and a second fiber layer stacked in the thickness direction, and includes a fiber fusion portion located at a cross section between the fibers. The first fiber layer has a concavo-convex structure including a plurality of convex portions and a bottom portion provided between adjacent convex portions, wherein each of the plurality of convex portions includes a top portion and a wall portion supporting the top portion, and an opening portion penetrating in the thickness direction is arranged at the bottom portion. The second fiber layer is provided on the side of the first fiber layer having the bottom. The second fiber layer has, on a surface facing the first fiber layer, a protruding portion extending from the opening portion of the first fiber layer into a region partitioned by the wall portion.

2. The nonwoven fabric for absorbent articles according to claim 1, wherein The raised portion can be observed from the first fiber layer side.

3. The nonwoven fabric for absorbent articles according to claim 1 or 2, wherein: The surface side of the second fiber layer facing the first fiber layer becomes a continuous fiber layer extending in the planar direction.

4. The nonwoven fabric for absorbent articles according to any one of claims 1 to 3, wherein In the contact region between the wall portion of the first fiber layer and the second fiber layer, there is a fiber fusion portion located at an intersection between fibers of the wall portion and fibers of the second fiber layer.

5. The nonwoven fabric for absorbent articles according to any one of claims 1 to 4, wherein The lower edge of the raised portion is connected to a contact region between the wall portion of the first fiber layer and the second fiber layer.

6. The nonwoven fabric for absorbent articles according to any one of claims 1 to 5, wherein In the contact region between the wall portion of the first fiber layer and the second fiber layer, fibers of the second fiber layer are oriented in a planar direction, and fibers on the surface of the lower edge of the protrusion have a fiber orientation different from that of fibers in the wall portion. 7 . The nonwoven fabric for absorbent articles according to claim 1 , further comprising a valley formed by a base of the wall portion constituting the convex portion and a lower edge of the raised portion extending toward the base.

8. The nonwoven fabric for absorbent articles according to claim 7, wherein The lower edge portion is connected to a contact region between the wall portion of the first fiber layer and the second fiber layer.

9. The nonwoven fabric for absorbent articles according to claim 7 or 8, wherein In a region where the root of the wall portion contacts the second fiber layer, the root is embedded in the second fiber layer and integrated therewith.

10. The nonwoven fabric for absorbent articles according to any one of claims 1 to 9, wherein The ratio of the thickness H2 of the protruding portion to the thickness H1 of the first fiber layer, that is, H2 / H1, 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.

11. The nonwoven fabric for absorbent articles according to any one of claims 1 to 10, wherein The ratio of the fiber diameter D2 of the fibers of the second fiber layer M2 to the fiber diameter D1 of the fibers of the first fiber layer, i.e. D2 / D1, 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.

12. The nonwoven fabric for absorbent articles according to any one of claims 1 to 11, wherein In the first fiber layer, a hollow region 1C exists on the back side of the convex portion.

13. The nonwoven fabric for absorbent articles according to any one of claims 1 to 12, which has a basis weight of 20 g / m 2 Above and 100g / m 2 the following.

14. The nonwoven fabric for absorbent articles according to any one of claims 1 to 13, wherein 4.9 mN / cm 2 The thickness under load is 0.8 mm or more and 10 mm or less.

15. The nonwoven fabric for absorbent articles according to any one of claims 1 to 14, wherein The fibers of the wall are oriented longitudinally.

16. The nonwoven fabric for absorbent articles according to claim 15, wherein The longitudinal orientation ratio of the fibers in the wall portion is 60% or more.

17. The nonwoven fabric for absorbent articles according to any one of claims 5 to 16, wherein The longitudinal orientation ratio of fibers on the surface of the lower edge portion is less than 45%.

18. The nonwoven fabric for absorbent articles according to claim 17, wherein The difference in longitudinal orientation rate between the fibers on the surface of the lower edge portion and the fibers in the wall portion is 15% or more.

19. The nonwoven fabric for absorbent articles according to any one of claims 1 to 18, wherein In a plan view from one surface side, the convex portion as the first fiber layer has a plurality of ridge portions and a saddle portion connecting adjacent ridge portions, the plurality of ridge portions extending in a direction Y and arranged apart from each other in a direction X intersecting the direction Y.

20. The nonwoven fabric for absorbent articles according to claim 19, wherein The saddle portion includes a top portion on one surface side and a wall portion supporting the top portion.

21. The nonwoven fabric for absorbent articles according to any one of claims 1 to 20, wherein The fibers constituting the second fiber layer have a smaller fiber diameter than the fibers constituting the first fiber layer.

22. The nonwoven fabric for absorbent articles according to claim 21, wherein The difference between the fiber diameter of the constituent fibers of the second fiber layer and the fiber diameter of the constituent fibers of the first fiber layer is 2 μm or more, preferably 3 μm or more, and more preferably 4 μm or more.

23. The nonwoven fabric for absorbent articles according to claim 21 or 22, wherein: The difference between the fiber diameter of the constituent fibers of the second fiber layer and the fiber diameter of the constituent fibers of the first fiber layer is 50 μm or less, preferably 40 μm or less, and more preferably 30 μm or less.

24. The nonwoven fabric for absorbent articles according to any one of claims 1 to 23, wherein The hydrophilicity of the constituent fibers of the second fiber layer is higher than the hydrophilicity of the constituent fibers of the first fiber layer.

25. The nonwoven fabric for absorbent articles according to claim 24, wherein The difference G1-G2 between the contact angle G1 of the constituent fibers of the first fiber layer and the contact angle G2 of the constituent fibers of the second fiber layer is 0.5 or more and 50.0 or less, preferably 1.0 or more, more preferably 2.0 or more, and preferably 45.0 or less, more preferably 40.0 or less.

26. The nonwoven fabric for absorbent articles according to any one of claims 1 to 25, wherein The number of fibers per unit area of ​​the second fiber layer is greater than the number of fibers per unit area of ​​the top portion of the first fiber layer.

27. The nonwoven fabric for absorbent articles according to claim 26, wherein The difference between the number of fibers per unit area of ​​the second fiber layer and the number of fibers per unit area of ​​the top portion of the first fiber layer is greater than 5 and less than 190, preferably greater than 8, more preferably greater than 10, and preferably less than 185, more preferably less than 180.

28. An absorbent article comprising the nonwoven fabric for absorbent articles according to any one of claims 1 to 27.

29. A method for producing a nonwoven fabric for an absorbent article, the method comprising: A pressing step of placing a first fiber web on a support having a concavo-convex shape with a plurality of protrusions and concave portions between the protrusions, pressing the first fiber web along the concave portions with a pressing portion of a pressing member to shape the fiber web, and opening holes at locations corresponding to the protrusions to form a concavo-convex open-pore fiber web having an open-pore surface on a side opposite to the support; After removing the pressing member from the support, blowing a first hot air to the concave-convex open-pore fiber web to fuse the fibers to obtain a concave-convex open-pore nonwoven fabric; A step of supplying a second fiber web and laminating it on the open hole side of the concavo-convex open hole nonwoven fabric; as well as A heat fusion step of blowing a second hot air to fuse the fibers of the concavoconvex nonwoven fabric and the second fiber web to each other, and to fuse the fibers in the second fiber web to each other.

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