Nonwoven fabric and absorbent article containing the same as a component

Abstract

To provide a nonwoven fabric excellent in cushioning property, and capable of obtaining soft touch, and an absorbent article including the same.SOLUTION: A nonwoven fabric 10 of the present invention comprises a first layer 11 containing a thermally fusible fiber, and a second layer 12 containing a thermally shrinkable fiber, where both layers are adjacently arranged so that a second face 11r of the first layer 11 faces a first face 12f of the second layer 12. A first face 11f of the first layer 11 is convexo-concave-shaped, and the second face 11r is convexo-concave-shaped so as to correspond to the convexo-concave shape of the first face 11f. A second face 12r of the second layer 12 is flat. A plurality of convex parts 15 and concave parts 16 are formed on a first face F side of the nonwoven fabric 10 by bonding the first layer 11 and the second layer 12 at a position of a concave part 11b of the first face 11f of the first layer 11. When observing along a thickness direction Z of the nonwoven fabric 10, the convex parts 15 has a lower existing density of fibers in an order of a top part 15a, a middle part 15b, and the second layer 12.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a nonwoven fabric and an absorbent article containing the same as a constituent member. [Background technology]

[0002] Absorbent articles such as disposable diapers are generally constructed with a sheet member made of a fibrous material. For example, absorbent articles generally include a liquid-retaining absorbent body and a topsheet that is in contact with the wearer's skin on the skin-facing side of the absorbent body. The present applicant previously disclosed a three-dimensional sheet material that can be used as the topsheet, in which a first layer and a second layer exhibiting elastomeric behavior are partially joined by a joint, the first layer forming a three-dimensional shape between the joints, and the entire sheet exhibiting elastomeric behavior and having breathability (Patent Document 1).

[0003] The present applicant has also previously disclosed a nonwoven fabric having two sheets each having a protruding portion protruding from one surface side and having an internal space, and another protruding portion protruding from the other surface side and having an internal space, the two sheets being arranged alternately and continuously in different directions in which the protruding portions intersect in a plan view, the protruding portions being arranged opposite each other in the thickness direction of the two sheets so that the protruding directions are opposite each other, and the other protruding portions being joined together (Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-187228 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-194333 Summary of the Invention [Problem to be solved by the invention]

[0005] Providing an absorbent article with a surface sheet having an uneven shape is effective in terms of improving breathability and conformability to the wearer's skin. However, there is a concern that the uneven surface of the sheet may be crushed by the wearer's body pressure, resulting in a decrease in cushioning and a lack of softness. The sheets described in Patent Documents 1 and 2 have room for improvement in terms of providing excellent cushioning and a soft feel.

[0006] Therefore, the present invention relates to providing a nonwoven fabric that has excellent cushioning properties and provides a soft feel, and an absorbent article that includes the nonwoven fabric as a constituent member. [Means for solving the problem]

[0007] The present invention relates to a nonwoven fabric comprising a first layer having a first side and a second side and comprising heat-fusible fibers, and a second layer having a first side and a second side and comprising heat-shrinkable fibers, the two layers being arranged adjacent to each other so that the second side of the first layer faces the first side of the second layer. The nonwoven fabric preferably has a first surface of the first layer that has an uneven shape, and a second surface that has an uneven shape that corresponds to the uneven shape of the first surface. The second surface of the second layer is preferably flat. In the nonwoven fabric, it is preferable that the first layer and the second layer are joined at the positions of the recesses on the first surface of the first layer, so that a plurality of protrusions and recesses are formed on the first surface side of the nonwoven fabric. When viewed along the thickness direction of the nonwoven fabric, the convex portions have a top portion, a bottom portion, and an intermediate portion located between the top portion and the bottom portion, It is preferable that the density of fibers decreases in the order of the top portion, the intermediate portion, and the second layer.

[0008] The present invention also relates to an absorbent article. The absorbent article preferably includes the nonwoven fabric as a constituent member. [Effects of the Invention]

[0009] The nonwoven fabric of the present invention has excellent cushioning properties and a soft feel. Furthermore, the absorbent article of the present invention provides a soft feel when in contact with the skin, and is therefore excellent in texture and comfort when worn. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing one embodiment of a nonwoven fabric of the present invention, and is a cross-sectional view passing through the apexes of the protrusions of the nonwoven fabric. [Figure 2] FIG. 2 is an enlarged cross-sectional view of the protrusion shown in FIG. [Figure 3] FIG. 3 is a cross-sectional view of a disposable diaper, which is one embodiment of the absorbent article of the present invention, taken along the lateral direction of the crotch portion. [Figure 4] FIG. 4 is a cross-sectional view showing the protrusions of the laminate before (a) and after (b) heat treatment. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will now be described based on preferred embodiments thereof with reference to the drawings. Figures 1 and 2 show one embodiment of a nonwoven fabric of the present invention. The nonwoven fabric 10 of this embodiment has a first side F and a second side R located opposite the first side F, and further has a laminated structure in which a first layer 11 and a second layer 12 are laminated. The first layer 11 forms the first side F of the nonwoven fabric 10, and the second layer 12 forms the second side R of the nonwoven fabric 10. The first layer 11 has a first side 11f and a second side 11r located opposite the first side 11f. The second layer 12 also has a first side 12f and a second side 12r located opposite the first side 12f. In the nonwoven fabric 10 of this embodiment, the first layer 11 and the second layer 12 are disposed adjacent to each other such that the second side 11r of the first layer 11 faces the first side 12f of the second layer 12.

[0012] The first layer 11 contains heat-fusible fibers. Heat-fusible fibers are fibers that fuse together under the action of heat and are made from thermoplastic resin. Examples of thermoplastic resins include polyolefins such as polyethylene (PE) and polypropylene (PP); polyesters such as polyethylene terephthalate (PET); polyamides such as nylon 6 and nylon 66; polyacrylic acid, polymethacrylic acid alkyl ester, polyvinyl chloride, and polyvinylidene chloride. These may be used alone or in combination of two or more. Furthermore, as the heat-fusible fiber, a composite fiber composed of two or more components, a low-melting point component and a high-melting point component, may be used. Such composite fibers are preferably core-sheath composite fibers, with the core preferably made of high-melting point PET or PP and the sheath preferably made of low-melting point PET, PP or PE. The core-sheath composite fiber may be of either a concentric type or an eccentric type.

[0013] From the viewpoint of further improving the bonding strength between the first layer 11 and the second layer 12, the content of the heat-fusible fibers in the first layer 11 is preferably 30% or more, more preferably 50% or more, and preferably 100% or less, and is preferably 30% or more and 100% or less, more preferably 50% or more and 100% or less, relative to the total mass of the first layer 11.

[0014] To further improve the softness of the nonwoven fabric 10, the fineness of the constituent fibers of the first layer 11 is preferably 0.1 dtex or more, more preferably 0.5 dtex or more, and is preferably 10 dtex or less, more preferably 4 dtex or less, and is preferably 0.1 dtex or more and 10 dtex or less, more preferably 0.5 dtex or more and 4 dtex or less. The fineness is measured by the following method.

[0015] <Method for measuring fineness> Fineness can be determined as the mass of fiber per 10,000 m of fiber by measuring the specific gravity of the constituent fibers and the cross-sectional area of ​​the fiber. For example, 1 dtex represents 1 g of mass per 10,000 m of fiber.

[0016] From the same viewpoint as above, the basis weight of the first layer 11 is preferably 10 g / m 2 More preferably, 15 g / m 2 and preferably 50 g / m 2 Less than 40 g / m 2 and preferably 10 g / m 2 More than 50g / m 2 Less than 15 g / m, more preferably 2 More than 40g / m 2 The following is the result.

[0017] The second layer 12 contains heat-shrinkable fibers. Heat-shrinkable fibers are fibers with heat-shrinkability that shrink when heat is applied. The heat-shrinkable fibers contained in the second layer 12 of this embodiment are heat-shrunk by the heating process described below, but still retain heat-shrinkability. Suitable heat-shrinkable fibers are those made of thermoplastic resins and have heat-shrinkability. Examples of such fibers include latently crimpable fibers. Latently crimpable fibers can be handled in the same way as conventional fibers for nonwoven fabrics before heating, and have the property of developing a spiral crimp and shrinking when heated at a predetermined temperature. Latently crimpable fibers are, for example, eccentric core-sheath or side-by-side bicomponent fibers composed of two thermoplastic polymer materials with different shrinkage rates. Examples include those described in JP-A-9-296325 and JP-A-2759331.

[0018] From the viewpoint of more reliably ensuring the height of the convex portions 15 described below, the content of the heat-shrinkable fiber in the second layer 12 is preferably 30% by mass or more, more preferably 50% by mass or more, and preferably 100% by mass or less, relative to the total mass of the second layer 12, and is preferably 30% by mass or more and 100% by mass or less, more preferably 50% by mass or more and 100% by mass or less.

[0019] To further improve the softness of the nonwoven fabric 10, the fineness of the constituent fibers of the second layer 12 is preferably 0.5 dtex or more, more preferably 1.0 dtex or more, and is preferably 10 dtex or less, more preferably 5 dtex or less, and is preferably 0.5 dtex or more and 10 dtex or less, more preferably 1.0 dtex or more and 5 dtex or less.

[0020] From the same viewpoint as above, the basis weight of the second layer 12 is preferably 5 g / m 2 More preferably, 15 g / m 2 and preferably 50 g / m 2 Less than 40 g / m 2 and preferably 5 g / m 2 More than 50g / m 2 Less than 15 g / m, more preferably 2 More than 40g / m 2 The following is the result.

[0021] As shown in FIG. 1 , the first layer 11 of the nonwoven fabric 10 has a plurality of convex portions 11a and concave portions 11b. When the first layer 11 is viewed from the first surface 11f side, the convex portions 11a and concave portions 11b of this embodiment are alternately and continuously arranged across the entire surface of the first layer 11 along two different directions that intersect with each other in a plan view (not shown). In the first layer 11, a space V is formed on the second surface 11r side of the convex portions 11a, and the second surface 11r side of the concave portions 11b protrudes toward the second layer 12. That is, when the first layer 11 is viewed from the second surface 11r side, the convex portions 11a are concave portions recessed toward the first surface 11f, and the concave portions 11b are convex portions protruding toward the second surface 11r. In this way, the first surface 11f of the first layer 11 has an uneven shape, and the second surface 11r has an uneven shape corresponding to the uneven shape of the first surface 11f.

[0022] The second surface 12r of the second layer 12 in the nonwoven fabric 10 is flat. In the second layer 12 in this embodiment, both the first surface 12f and the second surface 12r are flat. The first layer 11 and the second layer 12 are joined at the position of the recess 11b on the first surface 11f of the first layer 11. Specifically, the first layer 11 and the second layer 12 are joined via a joint 13 formed in the recess 11b of the first layer 11. The joint 13 in this embodiment is formed by melting and solidifying the heat-fusible fibers of the first layer 11. The joint 13 is a very thin portion, but for ease of explanation, the thickness of the joint 13 is illustrated in FIG. 1 as being significantly larger.

[0023] The nonwoven fabric 10 has a first layer 11 with an uneven shape on the first surface (F), thereby forming a plurality of convex portions 15 and concave portions 16 on the first surface (F). On the other hand, the second surface (R) of the nonwoven fabric 10 is formed by the second surface (12r) of the second layer 12, and is therefore flat. In this nonwoven fabric 10, the openings of the spaces (V) formed on the second surface (11r) side of the convex portions 11a of the first layer 11 are closed by the second layer 12. As a result, the convex portions 15 having hollow portions (V) therein are formed in the nonwoven fabric 10. The hollow portions (V) are portions where the constituent fibers of the first layer 11 and the second layer 12 are substantially absent.

[0024] When nonwoven fabric 10 is viewed from the first surface F, protrusions 15 and depressions 16 are arranged alternately and continuously along two different directions that intersect in a plan view over the entire surface of nonwoven fabric 10. In Figures 1 and 2, one of these two different directions is illustrated as the X direction.

[0025] When viewed along the thickness direction Z of the nonwoven fabric 10, the protrusions 15 in the nonwoven fabric 10 have a peak 15a, a bottom 15c, and an intermediate portion 15b located between the peak 15a and the bottom 15c (see FIG. 2). That is, the protrusions 15 have, in order from the apex of the protrusions 15 in the thickness direction Z, a peak 15a, an intermediate portion 15b, and a bottom 15c. The peaks 15a, intermediate portions 15b, and bottoms 15c are divided as follows in a cross section passing through the apex of the protrusions 15: In this specification, the "apex" of each portion of a protrusion or the like means the highest position of the portion in the thickness direction Z of the nonwoven fabric 10, i.e., in the height direction of the protrusions 15. As shown in Figure 2, the tops 15a of the protrusions 15 are the portions between the apexes of the protrusions 15 and the apexes of the hollow portions V in the thickness direction Z of the nonwoven fabric 10 (the height direction of the protrusions 15). The bottoms 15c of the protrusions 15 are formed by the second layer 12. That is, the bottoms 15c are the portions where the second layer 12 is located. The middle portions 15b of the protrusions 15 are the portions between the apexes of the hollow portions V and the first surface 12f of the second layer 12 in the thickness direction Z of the nonwoven fabric 10 (the height direction of the protrusions 15).

[0026] In the nonwoven fabric 10, the fiber density decreases in the order of the tops 15a of the protrusions 15, the intermediate portions 15b, and the second layer 12. That is, the fiber density in each portion of the protrusions 15 in the nonwoven fabric 10 satisfies the following magnitude relationship (1). r1 <r2<r3···(1) r1: density of fibers at the top 15a of the convex portion 15 r2: fiber density in the middle portion 15b of the protrusion 15 r3: Density of fibers in the bottom 15c (second layer 12) of the convex portion 15

[0027] The protrusions 15 whose fiber density satisfies the above-mentioned relationship (1) have good cushioning properties and are not easily crushed even when pressed, so that the protrusions 15 can be maintained high and the texture of the protrusions 15 can be easily maintained. A nonwoven fabric 10 having such protrusions 15 has excellent cushioning properties and provides a soft feel when in contact with the skin. This nonwoven fabric 10 is suitable for use as a component of an absorbent article, particularly as a component that comes into contact with the skin (e.g., a topsheet).

[0028] [Measurement of fiber density] The density of fibers present in the tops 15a, middles 15b, and bottoms 15c (second layer 12) of the convex portions 15 of the nonwoven fabric 10 is measured by the following method. The nonwoven fabric 10 to be measured is cut using a sharp razor so as to pass through the tops of the convex portions 15. The cut surface of this nonwoven fabric 10 is observed under magnification using a scanning electron microscope (for example, JCM-5100 manufactured by JEOL Ltd.). The magnification during observation is adjusted to a magnification (150 to 500 times) that allows measurement of approximately 30 to 60 fiber cross sections. The center of the observation field during observation is near the center of the thickness of each of the tops 15a, middles 15b, and second layer 12 (bottoms 15c of the convex portions 15). Next, a certain field area (0.5 mm2) is measured within the observation field of the cut surface. 2 ) and divide this into 1 mm 2 The above measurements are carried out for three arbitrarily selected convex portions 15, and the average of these measurements is calculated as the fiber density (counts / mm 2 )

[0029] From the viewpoint of further improving softness, the dimensions of the protrusions 15 are preferably within the following ranges. The height of the protrusions 15 and each part of the protrusions 15 is measured using a thickness measuring device with a load of 0.05 kPa applied to the nonwoven fabric 10. As the thickness measuring device, for example, a laser displacement meter (manufactured by KEYENCE Corporation, LK-080) can be used. The ratio (W / H) of the maximum length W (see FIG. 2) at the bottom 15c of each protrusion 15 to the height H (see FIG. 2) of the protrusion 15 is preferably 2.0 or less, more preferably 1.7 or less, also preferably 0.17 or more, more preferably 0.4 or more, and also preferably 0.17 to 2.0, more preferably 0.4 to 1.7. The maximum length W at the bottom 15c of each protrusion 15 is the maximum length between the bonded portions 13 located on both sides of the protrusion 15. The height H of each protrusion 15 is the length by which the protrusion 15 protrudes from the second layer 12 in the thickness direction Z of the nonwoven fabric 10. The height H of each protrusion 15 and the maximum length W of the bottom 15c can be measured using the observation method described in [Measurement of fiber density]. The ratio (H1 / H) of the height H1 (see FIG. 2) of the tops 15a of the protrusions 15 to the height H (see FIG. 2) of the protrusions 15 is preferably 0.05 or more, more preferably 0.1 or more, and is preferably 0.83 or less, more preferably 0.7 or less, and is preferably 0.05 or more and 0.83 or less, more preferably 0.1 or more and 0.7 or less. The height H1 of the tops 15a of the protrusions 15 is the length from the apex of the protrusions 15 to the apex of the hollow portion V in the thickness direction Z of the nonwoven fabric 10. The ratio (H2 / H) of the height H2 (see FIG. 2) of the intermediate portions 15b of the protrusions 15 to the height H (see FIG. 2) of the protrusions 15 is preferably 0.05 or more, more preferably 0.1 or more, and is preferably 0.83 or less, more preferably 0.7 or less, and is preferably 0.05 or more and 0.83 or less, more preferably 0.1 or more and 0.7 or less. The height H2 of the intermediate portions 15b of the protrusions 15 is the length from the apex of the hollow portion V to the first surface 12f of the second layer 12 in the thickness direction Z of the nonwoven fabric 10.

[0030] The height H of the convex portion 15 (see FIG. 2) is preferably 0.5 mm or more, more preferably 1.0 mm or more, and is preferably 6.0 mm or less, more preferably 5.0 mm or less, and is preferably 0.5 mm or more and 6.0 mm or less, more preferably 1.0 mm or more and 5.0 mm or less. The height H1 (see Figure 2) of the top 15a of the convex portion 15 is preferably 0.3 mm or more, more preferably 0.5 mm or more, and is preferably 5.0 mm or less, more preferably 4.0 mm or less, and is preferably 0.3 mm or more and 5.0 mm or less, more preferably 0.5 mm or more and 4.0 mm or less. The height H2 (see Figure 2) of the intermediate portion 15b of the convex portion 15 is preferably 0.3 mm or more, more preferably 0.5 mm or more, and is preferably 5.0 mm or less, more preferably 4.0 mm or less, and is preferably 0.3 mm or more and 5.0 mm or less, more preferably 0.5 mm or more and 4.0 mm or less. The maximum length W (see Figure 2) at the bottom 15c of the convex portion 15 is preferably 1.0 mm or more, more preferably 2.0 mm or more, and preferably 12.0 mm or less, more preferably 10.0 mm or less, and preferably 1.0 mm or more and 12.0 mm or less, more preferably 2.0 mm or more and 10.0 mm or less.

[0031] From the viewpoint of further improving the cushioning properties of the protrusions 15, the density of fibers present in each portion of the protrusions 15 of the nonwoven fabric 10 is preferably within the following range, provided that the density of fibers present satisfies the above-mentioned magnitude relationship (1). The fiber density r1 at the top 15a of the convex portion 15 is preferably 5% or more, more preferably 10% or more, and preferably 30% or less, more preferably 20% or less, relative to the fiber density r3 at the bottom 15c of the convex portion 15, and is preferably 5% or more and 30% or less, more preferably 10% or more and 20% or less. The fiber density r2 in the middle portion 15b of the convex portion 15 is preferably 10% or more, more preferably 20% or more, and is preferably 60% or less, more preferably 50% or less, and is preferably 10% or more and 60% or less, more preferably 20% or more and 50% or less, of the fiber density r3 in the bottom portion 15c of the convex portion 15. The density r1 of the fibers at the top 15a of the protrusion 15 is preferably 30 fibers / mm 2 More preferably, 50 lines / mm 2 or more, and preferably 300 lines / mm 2 Less than or equal to 200 lines / mm 2 and preferably 30 lines / mm 2 Over 300 lines / mm 2 Less than or equal to 50 lines / mm 2 Over 200 lines / mm 2 The following is the result. The density r2 of the fibers in the intermediate portion 15b of the protrusion 15 is preferably 50 fibers / mm 2 More preferably, 100 lines / mm 2 or more, and preferably 500 lines / mm2 Less than or equal to 400 lines / mm 2 and preferably 50 lines / mm 2 Over 500 lines / mm 2 Less than or equal to 100 lines / mm 2 Over 400 lines / mm 2 The following is the result. The density r3 of the fibers at the bottom 15c of the convex portion 15 is preferably 500 fibers / mm 2 More preferably, 600 lines / mm 2 or more, and preferably 1000 lines / mm 2 Less than or equal to 900 lines / mm 2 and preferably 500 lines / mm 2 Over 1000 lines / mm 2 Less than or equal to 600 lines / mm, more preferably 2 Over 900 lines / mm 2 The following is the result.

[0032] The nonwoven fabric 10 of this embodiment has excellent cushioning properties and a soft feel, and is therefore preferably used as a component of absorbent articles such as diapers. The term "absorbent article" as used herein broadly encompasses articles used to absorb body fluids (urine, loose stools, menstrual blood, sweat, etc.) discharged from the human body, such as disposable diapers, sanitary napkins, sanitary shorts, and incontinence pads.

[0033] An absorbent article including the nonwoven fabric 10 of this embodiment as a constituent member preferably includes the nonwoven fabric 10 as a constituent member that comes into contact with the wearer's skin. A preferred embodiment of such an absorbent article will be described with reference to FIG.

[0034] A disposable diaper 1 (hereinafter simply referred to as "diaper 1") generally has an elongated shape having a longitudinal direction corresponding to the direction extending from the wearer's ventral side through the crotch region to the dorsal side, and a transverse direction Y1 perpendicular to the longitudinal direction. The diaper 1 has a crotch region located in the wearer's crotch region, and a ventral region and a dorsal region extending in front and behind the crotch region. Figure 3 is a cross-sectional view of the crotch region of the diaper 1 taken along the transverse direction Y1 of the diaper 1.

[0035] The diaper 1 comprises a liquid-permeable topsheet 2, a liquid-impermeable or poorly liquid-permeable or water-repellent backsheet 3, and a liquid-retentive absorbent body 4 interposed between these two sheets. The topsheet 2 is disposed on the skin-facing side of the absorbent body 4, and the backsheet 3 is disposed on the non-skin-facing side of the absorbent body 4. The absorbent body 4 is the main liquid-absorbing part of the diaper 1 and comprises an absorbent core 40 that has the function of absorbing and retaining body fluids such as urine, and a core wrap sheet 41 that covers the absorbent core 40.

[0036] The "skin-facing side" refers to the side of a diaper or its constituent parts (e.g., absorbent body) that faces the wearer's skin when the diaper is worn, and the "non-skin-facing side" refers to the side that faces away from the wearer's skin when the diaper is worn. Furthermore, "when worn" and "worn state" refer to the state in which the diaper is worn while maintaining the proper wearing position.

[0037] A pair of stand-guard-forming sheets 6, 6 are arranged on both sides of the topsheet 2. The stand-guard-forming sheet 6 has an elastic member 61 for forming the stand-guard at its inner end in the lateral direction Y1. When the diaper 1 is worn, the elastic member 61 contracts to form a stand-guard that stands up toward the wearer's skin.

[0038] In the crotch portion of the diaper 1, leg elastic members 7 are arranged in a stretched state on the outer side in the lateral direction Y1 of the upright guard forming sheet 6. When the leg elastic members 7 contract, leg gathers are formed in the crotch portion, improving the fit around the legs of the wearer.

[0039] The diaper 1 of this embodiment includes the above-mentioned nonwoven fabric 10 as the topsheet 2. The topsheet 2 comes into contact with the wearer's skin when worn. From the viewpoint of achieving a soft feel when in contact with the wearer's skin, the topsheet 2 (nonwoven fabric 10) is preferably arranged so that the surface on the first layer 11 side faces the skin. This provides a good feel and wearing comfort. Furthermore, such a topsheet 2 has excellent absorbency of liquids such as urine, since a gradient in fiber density occurs from the skin-facing surface to the non-skin-facing surface due to the size relationship (1).

[0040] Next, a method for manufacturing the nonwoven fabric of the present invention will be described using the method for manufacturing the nonwoven fabric 10 of the above-described embodiment as an example. The method for manufacturing the nonwoven fabric 10 includes a lamination step of overlapping the first sheet 11s and the second sheet 12s, a joining step of joining the first sheet 11s and the second sheet 12s, and a heating step of heat-treating the joined first sheet 11s and second sheet 12s (see FIG. 4).

[0041] The first sheet 11s is a material forming the first layer 11 described above. Various types of nonwoven fabrics containing thermally adhesive fibers can be used as the first sheet 11s, including, for example, air-through nonwoven fabrics, spunbond nonwoven fabrics, spunlace nonwoven fabrics, meltblown nonwoven fabrics, resin-bonded nonwoven fabrics, needle-punched nonwoven fabrics, and laminates combining two or more of these nonwoven fabrics. The thermally adhesive fibers contained in the first sheet 11s and the content of the thermally adhesive fibers in the first sheet 11s are the same as those in the first layer 11 described above.

[0042] The first sheet 11s has an uneven shape consisting of a plurality of protrusions and recesses. Such a first sheet 11s can be manufactured, for example, by the manufacturing method described in Patent Document 2. Specifically, the first sheet 11s can be manufactured by a manufacturing method including the steps of: placing a web containing heat-fusible fibers on a breathable support having an uneven shape; blowing hot air (hereinafter also referred to as "first hot air") onto the web from the side opposite the support to shape the web to conform to the uneven shape of the support; and blowing second hot air, which is at a higher temperature than the first hot air, onto the shaped web on the support to fuse the fibers of the web together and fix the shaped shape. Alternatively, the first sheet 11s may be manufactured by feeding a strip-shaped sheet (nonwoven fabric) between two rolls whose peripheral surfaces interlock with each other and deforming the strip-shaped sheet into the uneven shape.

[0043] The second sheet 12s is a material for forming the second layer 12 described above. A web containing heat-shrinkable fibers can be used as the second sheet 12s. Such a web is typically produced by opening raw fibers such as heat-shrinkable fibers using a fiber opener and forming the opened raw fibers into a web using a carding machine. The heat-shrinkable fibers contained in the second sheet 12s and the content ratio of the heat-shrinkable fibers in the second sheet 12s are the same as those in the second layer 12 described above.

[0044] In the manufacturing method of this embodiment, the first sheet 11s and the second sheet 12s are overlapped in the laminating step, and the first sheet 11s and the second sheet 12s are joined at the positions of the recesses of the first sheet 11s in the joining step. Such joining can be achieved by a known joining method such as heat fusion such as embossing or by using an adhesive. The joining step may be performed after the lamination step. For example, after the first sheet 11s and the second sheet 12s are overlapped, the positions of the recesses in the first sheet 11s may be embossed to join the stacked first sheet 11s and second sheet 12s. Alternatively, the lamination step and the joining step may be performed almost simultaneously. For example, an adhesive may be applied to the portions of the recesses in the first sheet 11s that will come into contact with the second sheet 12s using a coating device such as a spray or a coater, and then the first sheet 11s and the second sheet 12s may be overlapped to join the first sheet 11s and the second sheet 12s. Through the above-described laminating step and bonding step, a laminate S in which the first sheet 11s and the second sheet 12s are bonded together is obtained.

[0045] The resulting laminate S has protrusions s1 and recesses s2 that correspond to the uneven shape of the first sheet 11s. From the viewpoint of ensuring the height of the protrusions 15 of the nonwoven fabric 10 more reliably, the height H3 of the protrusions s1 in the laminate S [see Figure 4(a)] is preferably 5% or more, more preferably 10% or more, and is preferably 95% or less, more preferably 90% or less, and is preferably 5% or more and 95% or less, more preferably 10% or more and 90% or less, of the height H of the protrusions 15 of the nonwoven fabric 10 obtained after the heating step. The height H3 of the convex portion s1 in the laminate S [see Figure 4(a)] is preferably 0.1 mm or more, more preferably 1.0 mm or more, and is preferably 5.4 mm or less, more preferably 5.0 mm or less, and is preferably 0.1 mm or more and 5.4 mm or less, more preferably 1.0 mm or more and 5.0 mm or less. From the same viewpoint as above, the maximum length W1 (see FIG. 4(a)) of the bottom of the protrusion s1 in the laminate S is preferably 1.1 mm or more, more preferably 2.0 mm or more, and preferably 20 mm or less, more preferably 10 mm or less, and is preferably 1.1 mm or more and 20 mm or less, more preferably 2.0 mm or more and 10 mm or less. The maximum length W1 of the bottom of the protrusion s1 in the laminate S is the maximum length between the joints 13 located on both sides of the protrusion s1 of the laminate S.

[0046] In the heating step, the laminate is heat-treated to form the nonwoven fabric 10. The heat treatment can be performed by blowing hot air onto the laminate, or by heating the laminate in a windless environment at a predetermined temperature.

[0047] The heating temperature of the laminate in the heating step is equal to or higher than the temperature at which the heat-shrinkable fiber begins to shrink. This heat treatment causes the heat-shrinkable fiber of the second sheet 12s to shrink, causing the convex portions s1 of the first sheet 11s to protrude toward the first surface F more than before the heat treatment (see FIGS. 4(a) and 4(b)). This allows the convex portions 15 of the nonwoven fabric 10 to be formed higher than before. Furthermore, as the heat-shrinkable fiber shrinks, the density of the fibers changes so as to satisfy the magnitude relationship (1) in the process of causing the convex portions s1 to protrude more than before the heat treatment. This is thought to be because the shrinkage causes the convex portions s1 to rise, increasing the thickness of the tops 15a and decreasing the density of the fibers, while the bottoms 15c shrink and increasing the density of the fibers.

[0048] From the viewpoint of formability of the protrusions 15, the temperature difference between the heating temperature of the laminate in the heating step and the temperature at which the heat-shrinkable fiber in the second sheet 12s starts to heat shrink is preferably 3°C or more, more preferably 5°C or more, and also preferably 30°C or less, more preferably 20°C or less, and preferably 3°C or more and 30°C or less, more preferably 5°C or more and 20°C or less. When the heat treatment is performed by blowing hot air onto the laminate S, the heating temperature is the temperature of the hot air. When the heat treatment is a method in which the laminate S is heated in a windless environment at a predetermined temperature, the heating temperature is the environmental temperature when the laminate is heated. From the viewpoint of ensuring the height of the protrusions 15 more reliably, it is preferable to use a method in which hot air is blown onto the laminate S as the heat treatment. The hot air velocity is preferably 0.1 m / sec or more, more preferably 0.3 m / sec or more, and preferably 3.0 m / sec or less, more preferably 2.0 m / sec or less, and is preferably 0.1 m / sec or more and 3.0 m / sec or less, more preferably 0.3 m / sec or more and 2.0 m / sec or less. In this case, it is preferable to blow the hot air from the second sheet 12s side of the laminate S, from the viewpoint of making it easier to maintain the height of the protrusions 15 and turning the second sheet 12s into a nonwoven fabric.

[0049] From the same viewpoint as above, the heating time (heat treatment time) of the laminate in the heating step is preferably 3 seconds or more, more preferably 5 seconds or more, and also preferably 30 seconds or less, more preferably 20 seconds or less, and is preferably 3 seconds or more and 30 seconds or less, more preferably 5 seconds or more and 20 seconds or less.

[0050] The present invention has been described above based on its preferred embodiments, but the present invention is not limited to the above embodiments and can be modified as appropriate within the scope of the invention. For example, in the above-described embodiment, the nonwoven fabric 10 is used as the topsheet 2 of the diaper 1, but it may also be used as a sheet member other than the topsheet 2. [Example]

[0051] The present invention will be described in more detail below with reference to examples, but the scope of the present invention is not limited to these examples.

[0052] Example 1 The nonwoven fabric 10 shown in Figure 1 was produced. First, a web made of heat-fusible fibers was prepared. The heat-fusible fibers were core-sheath type composite fibers, with the core made of polyethylene terephthalate (PET) and the sheath made of polyethylene (PE), and the mass ratio of the core to the sheath (core:sheath) was 6:4. The fineness of the core-sheath type composite fibers was 1.8 dtex. A first sheet was produced using the web made of the heat-fusible fibers by the method described in JP 2013-194333 (Patent Document 2). Specifically, the web was placed on a support shown in Figure 4 of the document, and a first hot air stream was blown onto the web to form a shape, followed by a second hot air stream to form a nonwoven fabric, thereby producing the first sheet. The support had projections with a MD pitch of 8 mm, a CD pitch of 5 mm in plan view, a projection height of 7.5 mm, and a hole diameter of 2.8 mm. The first hot air had a temperature of 130°C and a velocity of 50 m / s, and the second hot air had a temperature of 145°C and a velocity of 5 m / s. A second sheet was made of a web of heat-shrinkable fibers. The heat-fusible fibers were latently crimpable fibers made of polypropylene (PP). The latently crimpable fibers had a fineness of 3.3 dtex. Next, the first sheet and the second sheet were overlapped, and the recessed portions of the first sheet were embossed to bond the first sheet and the second sheet together to obtain a laminate. The laminate was then placed on a mesh belt, and a heating step was carried out by blowing hot air onto the laminate S to obtain nonwoven fabric 10. The heating conditions were a heating temperature (hot air temperature) of 105°C, a hot air velocity of 1.2 m / sec, and a heating time of 8 seconds. The basis weights and fiber finenesses of the first and second sheets are shown in Table 1.

[0053] Example 2 A nonwoven fabric was produced in the same manner as in Example 1, except that the heating time in the heating step was set to 11 seconds.

[0054] Example 3 A nonwoven fabric was produced in the same manner as in Example 1, except that the first sheet and the second sheet were made to have different basis weights and the heating time in the heating step was set to 11 seconds.

[0055] Example 4 A nonwoven fabric was produced in the same manner as in Example 1, except that the first sheet and the second sheet were made to have different basis weights and the heating time in the heating step was set to 11 seconds.

[0056] Comparative Example 1 A web made of heat-fusible fibers was prepared. The heat-fusible fibers were sheath-core composite fibers, with the core made of polyethylene terephthalate (PET) and the sheath made of polyethylene (PE), with a core-to-sheath mass ratio (core:sheath) of 6:4. The fineness of the sheath-core composite fibers was 2.0 dtex. A laminate was produced by laminating the web as a first sheet with the second sheet of Example 1. The laminate was then embossed to form bonded portions. The laminate was then placed on a mesh belt and subjected to a heating process by blowing hot air onto the laminate, resulting in a nonwoven fabric. The heating conditions were a heating temperature (hot air temperature) of 105°C, a hot air velocity of 1.2 m / s, and a heating time of 11 seconds. The nonwoven fabric had recesses at the bonded portions and protrusions at the other positions, with the interiors of the protrusions being solid.

[0057] Comparative Example 2 In Comparative Example 2, only the first sheet obtained in Example 1 was used as the nonwoven fabric.

[0058] For the nonwoven fabrics obtained in the Examples and Comparative Examples, the dimensions of the protrusions 15, the structure of the protrusions, and the density of fibers at each location on the protrusions 15 were measured using the methods described above. The measurement results are shown in Table 1. In addition, the compression properties and texture of each nonwoven fabric were evaluated using the methods described below. The evaluation results are shown in Table 1. The height of the protrusions in the nonwoven fabric of Comparative Example 1 was divided into thirds, with the top being 1 / 3 of the protrusion from the apex in the thickness direction of the nonwoven fabric and the remaining 2 / 3 being the middle. The bottom was the second sheet (second layer) of the nonwoven fabric.

[0059] [Evaluation of compression characteristics] It is generally known that compression characteristics such as compression work load can be expressed as measured values ​​using the KES (Kawabata Evaluation System) manufactured by Kato Tech Co., Ltd. (Reference: Standardization and Analysis of Texture Evaluation (2nd Edition), author Kawabata Toshio, published July 10, 1980). For the compression characteristics of the present examples and comparative examples, a compression tester KES-G5 manufactured by Kato Tech Co., Ltd. was used. First, the nonwoven fabric to be measured was attached to the test stand of the compression tester, and a 2 cm2 area was measured. 2 In this compression process, the compression speed was 0.2 cm / sec and the maximum compression load was 4902 mN / cm. 2 The compression work (WC) is expressed by the following formula (2), and its unit is "mN cm / cm 2 In the following formula, Tm is 4902 mN / cm 2 (4.9kPa) Thickness at load, T0, is 4.902mN / cm 2 (49 Pa) is the thickness under load. a is the measurement load during the compression process (mN / cm 2 The larger the compression work (WC) value, the softer the material.

[0060]

number

[0061] [Evaluation of texture] Evaluation sample pieces measuring 10 cm x 10 cm were cut out from the nonwoven fabrics of the Examples and Comparative Examples. The first side (the side on the first sheet side) of the evaluation sample was used as the evaluation target side. The evaluation sample pieces were placed on a table with the evaluation target side facing up, and the texture was evaluated by touching the evaluation sample pieces from the front. The texture evaluation was carried out by three adult males experienced in texture evaluation. Specifically, the evaluation was carried out on a 5-point scale from 1 to 5, with 5 indicating the best texture. The average of the scores from the three people was rounded to the nearest integer to obtain the texture score. The method of touching was not specified.

[0062] [Table 1]

[0063] As shown in Table 1, the height of the convex portions of each of the nonwoven fabrics of Examples 1 to 4 was 2.6 The nonwoven fabrics of each Example had greater compression properties (compression work load) than Comparative Example 1, and had excellent softness with WC values ​​of 3.9 or more. Furthermore, the nonwoven fabrics of each Example all had higher evaluations of texture than Comparative Examples 1 and 2. In addition, in the [Evaluation of Texture] above, when the evaluators touched the nonwoven fabrics of each Example, each nonwoven fabric felt cushiony. The above results demonstrate that the nonwoven fabrics of the present invention are excellent in cushioning properties and soft feel. [Explanation of symbols]

[0064] 10 Nonwoven fabric 11 1st layer 12 2nd layer 13 Joint 15 Convex part 15a Top 15b Middle part 15c bottom 16 Recess V Hollow part 1. Absorbent articles (disposable diapers) 2 Surface sheet 3 Back sheet 4. Absorber

Claims

1. A nonwoven fabric comprising a first layer having a first surface and a second surface and containing heat-fusible fibers, and a second layer having a first surface and a second surface and containing heat-shrinkable fibers, the first and second layers being disposed adjacent to each other such that the second surface of the first layer faces the first surface of the second layer, a first surface of the first layer has an uneven shape and a second surface has an uneven shape corresponding to the uneven shape of the first surface; the second surface of the second layer is flat; the first layer and the second layer are joined at the positions of the recesses on the first surface of the first layer, so that a plurality of protrusions and recesses are formed on the first surface side of the nonwoven fabric; When viewed along the thickness direction of the nonwoven fabric, the convex portions have a top portion, a bottom portion, and an intermediate portion located between the top portion and the bottom portion, the density of fibers decreases in the top portion, the middle portion, and the second layer; The density of the fibers at the top is 10% or more and 20% or less of the density of the fibers at the bottom, A nonwoven fabric, wherein the density of the fibers in the middle portion is 20% or more and 50% or less of the density of the fibers in the bottom portion.

2. 2. The nonwoven fabric according to claim 1, wherein the ratio (W / H) of the maximum length W of the bottom of each of the protrusions to the height H of each of the protrusions is 2.0 or less.

3. 3. The nonwoven fabric according to claim 1, wherein the height of the intermediate portion is 0.5 mm or more and 4.0 mm or less.

4. An absorbent article comprising the nonwoven fabric according to claim 1 or 2 as a constituent member.

5. The device comprises a liquid-retaining absorbent body and a top sheet disposed on the skin-facing side of the absorbent body, The absorbent article according to claim 4 , wherein the topsheet is the nonwoven fabric arranged so that the surface of the first layer faces the skin.

6. A method for producing the nonwoven fabric according to any one of claims 1 to 3, a step of overlapping a first sheet containing heat-fusible fibers and deformed into an uneven shape with a second sheet made of a web containing heat-shrinkable fibers; bonding the first sheet and the second sheet together by embossing the first sheet at the recessed positions; and heat-treating the joined first and second sheets at a temperature equal to or higher than the temperature at which the heat-shrinkable fibers begin to shrink.

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