JP7570773B2 - Nonwoven - Google Patents

Description

The present invention relates to nonwoven fabrics.

Nonwoven fabrics are often used in absorbent articles such as diapers. Technologies have been developed to give nonwoven fabrics various functions.

For example, Patent Document 1 describes the incorporation of a resin-bonded nonwoven fabric impregnated or coated with an adhesive into an absorbent article in order to improve the thickness recovery of the absorbent article. Specifically, the resin-bonded nonwoven fabric is disposed as a member of the absorbent article that does not come into contact with the skin.
Furthermore, Patent Documents 2 to 4 describe uneven nonwoven fabrics in which a fiber web is previously shaped into an uneven shape to form a nonwoven fabric, thereby improving compression recovery rate, cushioning properties, and the like.

JP 2001-187088 A JP 2012-136791 A JP 2019-44320 A

For example, when a nonwoven fabric is incorporated into a product such as an absorbent article and enclosed in a packaging bag, it is subjected to compression pressure, and is required to have excellent thickness recovery properties when removed from the packaging bag.
However, when attempting to increase the thickness without increasing the basis weight, the thickness recovery is still not sufficient compared to the thickness before encapsulation, and there is room for improvement. In this regard, the resin-bonded nonwoven fabric described in Patent Document 1 is formed by impregnating or applying an adhesive to the entire fiber assembly, so there is room for improvement in terms of feel compared to an air-through nonwoven fabric. Therefore, with a resin-bonded nonwoven fabric, it is difficult to further improve the thickness recovery while maintaining the fluffy texture of the nonwoven fabric.

In consideration of the above problems, the present invention relates to a nonwoven fabric that has excellent thickness recovery and maintains a fluffy texture.

The present invention is a nonwoven fabric that contains thermoplastic fibers and has fusion points between the fibers.
The nonwoven fabric of the present invention preferably has an apparent thickness of 4 mm or more under a load of 50 Pa.
The nonwoven fabric of the present invention preferably has an apparent thickness when pressed at 2.5 kPa that is equal to or less than half of the apparent thickness of the nonwoven fabric when pressed at 50 Pa.
The nonwoven fabric of the present invention preferably has (1) a recovery rate of the apparent thickness of the nonwoven fabric after being released from compression of 40% or more.
The nonwoven fabric of the present invention preferably has an apparent thickness (2) of 2 mm or more and 8 mm or less after being released from compression.
The nonwoven fabric of the present invention preferably satisfies either one or both of the above requirements (1) and (2).
The apparent thickness and thickness recovery rate of nonwoven fabric after compression and release in the above (1) and (2) are values obtained by the following (Method of Measuring Apparent Thickness and Thickness Recovery Rate of Nonwoven Fabric After Compression and Release).
(Method of measuring apparent thickness and thickness recovery rate of nonwoven fabric after releasing from compression)
(a) "Nonwoven fabric apparent thickness before compression": a load of 50 Pa is applied to a nonwoven fabric sample to measure its apparent thickness.
(b) Next, the nonwoven fabric of the measurement sample is compressed to 0.7 mm under a load of 20 kPa. This compressed state is maintained in an atmosphere at 50° C. for 24 hours, and then the compressed state is released and the sample is left in an atmosphere at 25° C. for 30 minutes.
(c) Then, a laser thickness gauge is used to measure the thickness under a load of 50 Pa. Measurements are taken at three locations, and the average value is taken as the measurement data to obtain the "apparent thickness of the nonwoven fabric after release from compression."
(d) Finally, the recovery rate of the nonwoven fabric apparent thickness is calculated using the following formula.
"Recovery rate of apparent thickness of nonwoven fabric after release from compression [%]"
= "apparent thickness of nonwoven fabric after compression and release" ÷ "apparent thickness of nonwoven fabric before compression" × 100

The above and other features and advantages of the present invention will become more apparent from the claims and the following description, taken in conjunction with the accompanying drawings.

The nonwoven fabric of the present invention has excellent thickness recovery and maintains a fluffy texture.

FIG. 2 is a schematic diagram showing a part of an observation screen used in a method for measuring the longitudinal orientation degree of fibers, together with a square reference line. FIG. 2 is a schematic diagram showing a portion of an observation image, together with a reference circle, used in a method for confirming the presence or absence of a binder on fiber intersections at the center of the thickness of a nonwoven fabric. 1A is a side view showing the position (line A-A) at which cross section A, which passes through the center of the thickness of a flat nonwoven fabric and is perpendicular to the fiber layer that forms the nonwoven fabric surface (plane), is cut out, and FIG. 1B is a side view showing the position (line B-B) at which cross section B, which passes through the center of the thickness of the nonwoven fabric and is perpendicular to cross section A, is cut out. 1A is a side view showing the position (line A-A) at which cross section A of a nonwoven fabric with a concave-convex shape is cut, the cross section A passing through the center of the thickness and perpendicular to the fiber layer that forms the nonwoven fabric surface (the concave-convex surface connecting the tops of the convex portions and the bottoms of the concave portions), and FIG. 1B is a side view showing the position (line B-B) at which cross section B passing through the center of the thickness and perpendicular to cross section A is cut. FIG. 2 is a partially sectional perspective view showing a schematic diagram of specific example 1 of the uneven shape of a nonwoven fabric. 1 is a photograph showing a plane view of one side of specific example 2 of a nonwoven fabric having a concave-convex shape. 7 is a partial cross-sectional view of the nonwoven fabric shown in FIG. 6 taken along the line CC. 7 is a partial cross-sectional view of the nonwoven fabric shown in FIG. 6 taken along the line D-D. 7 is a photograph showing a plan view of the opposite surface of the nonwoven fabric shown in FIG. 6 . 10 is a partial cross-sectional view of the nonwoven fabric shown in FIG. 9 taken along line EE. 10 is a partial cross-sectional view of the nonwoven fabric shown in FIG. 9 taken along the line FF. 1 is a schematic diagram illustrating the manufacturing process of a nonwoven fabric sample in Example 8, in which (A) is an explanatory diagram illustrating the process of placing a fiber web on a male support material and pressing a female support material into the male support material from above the fiber web, (B) is an explanatory diagram illustrating the process of directing a first hot air stream from above the female support material to shape the fiber web, and (C) is an explanatory diagram illustrating the process of removing the female support material and blowing a second hot air stream from above the shaped fiber web to fuse the fibers together.

Preferred embodiments of the nonwoven fabric of the present invention will now be described.
The nonwoven fabric of the present invention contains thermoplastic fibers and has fusion points between the fibers. The fusion points are the portions where the fibers are bonded to each other at the contact points between the intersecting fibers. More specifically, the fusion points are formed when the surfaces of the thermoplastic fibers are partially melted by heat treatment during the manufacturing process of the nonwoven fabric, and the fibers are bonded to each other by the melting. For example, an air-through nonwoven fabric is used as the nonwoven fabric of the present invention.

As the thermoplastic fiber, various types of fibers used in this type of article can be used without any particular restrictions. For example, polyester resins such as polyethylene terephthalate (hereinafter referred to as PET), polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, polylactic acid, and polybutylene succinate and their copolymers; various PE resins such as low-density polyethylene (hereinafter referred to as PE), medium-density PE, high-density PE, linear low-density PE, and ultra-high molecular weight PE; various polypropylene resins such as isotactic, atactic, and syndiotactic polypropylene (hereinafter referred to as PP) resins polymerized using a normal Ziegler-Natta catalyst or a metallocene catalyst; various polymethylpentene resins; various polyolefin resins such as ethylene-vinyl alcohol copolymer resin and ethylene-propylene copolymer resin; polyamide resins such as nylon 6, nylon 66, nylon 11, and nylon 12; and engineering plastics such as polycarbonate, polyacetal, polystyrene, and cyclic polyolefin can be used.

The nonwoven fabric of the present invention has an apparent thickness of 4 mm or more when subjected to a load of 50 Pa. Here, a load of 50 Pa means a load sufficient to suppress fluffing on the surface of the nonwoven fabric, and is a load necessary for properly measuring the apparent thickness of the nonwoven fabric. A load of 50 Pa is applied to the nonwoven fabric, for example, by placing a circular plate having a diameter of 2.5 cm and a mass of 2.45 g on the nonwoven fabric.
The aforementioned apparent thickness means the vertical distance between the horizontal plane and a virtual plane that is in contact with the outermost part of the side opposite to the one side of the nonwoven fabric that is in contact with the horizontal plane when the nonwoven fabric is placed on the horizontal plane (hereinafter, the vertical direction to the horizontal plane may be simply referred to as the "vertical direction"). The above "one side" and "opposite side" refer to the front and back sides of the nonwoven fabric, and are the side that is furthest from the horizontal plane in the vertical direction to the horizontal plane and the side that is closest to the horizontal plane. For example, when the nonwoven fabric of the present invention has an uneven shape on both sides, the apparent thickness is the vertical distance between the position of the top of the convexity on one side and the position of the top of the convexity on the other side.
In this specification, the one surface side is also referred to as a first surface side and may be designated by the symbol 1 A. The opposite surface side is also referred to as a second surface side and may be designated by the symbol 1 B. In the nonwoven fabric of this embodiment, the opposite surface (second surface) side is the surface side that does not come into contact with the skin during use (non-skin surface side).

(Method for measuring the apparent thickness of a nonwoven fabric under a load of 50 Pa)
The nonwoven fabric to be measured is cut to a size of 10 cm x 10 cm to prepare a measurement sample. Using a laser thickness gauge (high-precision displacement sensor ZS-LD80 (product name) manufactured by Omron Corporation; all laser thickness gauges used in this specification are of this type), the thickness of the measurement sample is measured under a load of 50 Pa. Measurements are taken at three locations, and the average value is regarded as the apparent thickness of the nonwoven fabric to be measured.
In addition, when the nonwoven fabric to be measured is incorporated into a product, the adhesive strength of the adhesive or the like is weakened by a cooling means such as a cold spray, and the nonwoven fabric is removed from the product and the above measurement is performed. This method of removing the nonwoven fabric is similarly applied to other measurements in this specification.
If it is not possible to take out a nonwoven fabric measuring 10 cm x 10 cm, take out a piece as large as possible.

The nonwoven fabric of the present invention preferably has the above-mentioned apparent thickness at a load of 50 Pa (vertical load), which gives it a fluffy texture. This is due to the degree of longitudinal orientation of the fibers, and the higher the degree of longitudinal orientation, the greater the bulk of the nonwoven fabric. Furthermore, the presence of longitudinally oriented fibers makes it possible to achieve high bulk despite a low basis weight. As a result, anyone who touches the nonwoven fabric of the present invention can feel the bulkiness due to the thickness and the soft feel.
From this viewpoint, the nonwoven fabric of the present invention more preferably has an apparent thickness of 5 mm or more under a load of 50 Pa, further preferably 6 mm or more, and particularly preferably 7 mm or more.
From the viewpoint of ensuring the strength of the nonwoven fabric, the nonwoven fabric of the present invention preferably has an apparent thickness of 9 mm or less, and more preferably 8.5 mm or less, under a load of 50 Pa.

In addition, the nonwoven fabric of the present invention preferably has an apparent thickness of 50% or less of the apparent thickness of the nonwoven fabric when pressurized at 2.5 kPa (pressurized vertically) at a load of 50 Pa. The above-mentioned pressurization at 2.5 kPa means a load that is normally assumed when the nonwoven fabric of the present invention is incorporated as a component of a nonwoven fabric product such as an absorbent article, and the nonwoven fabric product is sealed in a packaging bag as a package for sale. In other words, by making the apparent thickness of the nonwoven fabric when pressurized at 2.5 kPa below this upper limit, it becomes possible to compactly store a nonwoven fabric product having the nonwoven fabric of the present invention as a component in a packaging bag. Usually, the nonwoven fabric is compressed and sealed in a packaging bag, so that when a consumer opens and uses the bag, the nonwoven fabric has been in a compressed storage state due to the sealing. Therefore, evaluation assuming a compressed storage state is important. The apparent thickness of the nonwoven fabric when pressed at 2.5 kPa can be measured by setting the load to 2.5 kPa in the method described above (method for measuring the apparent thickness of a nonwoven fabric under a load of 50 Pa).

As a result, the nonwoven fabric of the present invention has a fluffy feel due to its sufficient thickness, while also having high compression properties that enable it to be enclosed in a package.
From this viewpoint, the nonwoven fabric of the present invention preferably has an apparent thickness when pressed at the above-mentioned 2.5 kPa of 33.3% or less, and even more preferably 25% or less, of the apparent thickness of the nonwoven fabric when pressed at a load of 50 Pa.
Furthermore, from the viewpoint of maintaining the fusion state of the fusion points between the fibers and maintaining the shape recovery of the fibers after the load is applied, the nonwoven fabric of the present invention preferably has an apparent thickness when pressed at the above-mentioned 2.5 kPa of the apparent thickness of the nonwoven fabric when pressed at a load of 50 Pa, preferably 10% or more, more preferably 12.5% or more, and even more preferably 16.7% or more.

At the same time, it is preferable that the nonwoven fabric of the present invention satisfies either or both of the following requirements (1) and (2) in terms of the values obtained by the following (method of measuring the apparent thickness and thickness recovery rate of nonwoven fabric after releasing from compression).
(1) The recovery rate of the apparent thickness of the nonwoven fabric after release from compression is 40% or more.
(2) The apparent thickness of the nonwoven fabric after compression and release is 2 mm or more and 8 mm or less.

(Method of measuring apparent thickness and thickness recovery rate of nonwoven fabric after releasing from compression)
(a) "Nonwoven fabric apparent thickness before compression" is determined by applying a load of 50 Pa to a nonwoven fabric sample and measuring its apparent thickness. This measurement is performed based on the above-mentioned (Method for measuring the apparent thickness of a nonwoven fabric under a load of 50 Pa).
(b) Next, the following "pressure treatment" is performed. The nonwoven fabric of the measurement sample is compressed to 0.7 mm with a load of 20 kPa. At this time, the nonwoven fabric is compressed to 0.7 mm by, for example, inserting a spacer. This compressed state is maintained in an atmosphere of 50°C for 24 hours, and then released from the compressed state and left in an atmosphere of 25°C for 30 minutes.
(c) Then, a laser thickness gauge is used to measure the thickness under a load of 50 Pa. Measurements are taken at three locations, and the average value is taken as the measurement data to obtain the "apparent thickness of the nonwoven fabric after release from compression."
(d) Finally, the recovery rate of the nonwoven fabric apparent thickness is calculated using the following formula.
"Recovery rate of apparent thickness of nonwoven fabric after release from compression [%]"
= "apparent thickness of nonwoven fabric after compression and release" ÷ "apparent thickness of nonwoven fabric before compression" × 100

As a result, the nonwoven fabric of the present invention has sufficient thickness while also having high compression properties and a fluffy feel, i.e., high cushioning properties, and also has high thickness recovery after being released from compression.
Such effects are further enhanced when the nonwoven fabric of the first invention has a longitudinal fiber orientation and/or a binder structure present at the fiber intersections, which will be described later.
More specifically, a low basis weight, bulky nonwoven fabric can be formed by using fibers with a high degree of longitudinal orientation, and the increased amount of compressive deformation due to buckling of the longitudinally oriented fibers can result in bulky and highly compressible fabric.
In addition, the presence of a binder at the fiber intersections suppresses crushing due to plastic deformation at the fiber fusion intersections, and the use of high core ratio fibers improves the relaxation modulus, making it possible to effectively achieve thickness recovery after release from compression.
This allows the nonwoven fabric of the present invention to maintain the fluffy texture even after compression. That is, the nonwoven fabric of the present invention allows the fabric to be enclosed in a highly compressed package while providing a sense of bulk due to its thickness and a soft feel due to compression, and allows the fabric to provide a sense of its original fluffy texture after opening the package. The nonwoven fabric of the present invention also achieves and maintains both sufficient thickness and excellent cushioning properties before and after compression.

From this viewpoint, the nonwoven fabric of the present invention more preferably has a recovery rate of the apparent thickness of 45% or more after the above-mentioned compression and release, and further preferably has a recovery rate of 50% or more.
From the same viewpoint, the nonwoven fabric of the present invention more preferably has an apparent thickness of 2.3 mm or more, and further preferably 2.5 mm or more, after the above-mentioned compression and release.
The greater the "recovery rate [%] of apparent thickness of nonwoven fabric after release from compression," the better the thickness recovery after release from compression.

From the viewpoint of providing a soft feel, the nonwoven fabric of the present invention preferably has an apparent thickness recovery rate after the above-mentioned compression and release of 80% or less, more preferably 70% or less, and even more preferably 60% or less.
From the same viewpoint, the nonwoven fabric of the present invention more preferably has an apparent thickness of 4 mm or less, and further preferably 3.8 mm or less, after the above-mentioned compression and release.

The nonwoven fabric of the present invention preferably has a deformation stroke of 1 mm or more, more preferably 1.5 mm or more, and even more preferably 2 mm or more, after being released from compression.
Furthermore, from the viewpoint of ensuring the strength of the nonwoven fabric in the thickness direction, the nonwoven fabric deformation stroke after the above-mentioned compression and release is preferably 6 mm or less, more preferably 5.5 mm or less, and even more preferably 5 mm or less.
As a result, the nonwoven fabric of the present invention, in addition to the above-mentioned properties, is able to better retain the amount of deformation that gives it a feeling of softness even after being sealed in a package.
The nonwoven fabric deformation stroke after compression and release is an index that indicates the cushioning properties of a nonwoven fabric after long-term compression, and is a quantification of the amount of deformation in the compression direction of the nonwoven fabric when compressed. The larger this value is, the fluffier the texture of the nonwoven fabric is. This makes it possible to quantitatively express the fluffiness and cushioning properties when a person touches the nonwoven fabric. By creating a nonwoven fabric configuration that increases the compression deformation stroke, it is possible to produce a nonwoven fabric that achieves a fluffier texture. This nonwoven fabric deformation stroke can be obtained by the following measurement method.

(Method for measuring nonwoven fabric deformation stroke after compression and release)
The nonwoven fabric to be measured is cut to 10 cm x 10 cm to prepare a measurement sample. If it is not possible to take out a nonwoven fabric of 10 cm x 10 cm size, take out a size as large as possible. The pressure treatment described above (Method of measuring the apparent thickness and thickness recovery rate of nonwoven fabric after compression and release) is performed. Then, a laser thickness meter is used to measure the thickness at a load of 50 Pa. Measurements are taken at three locations, and the average value is used as the measurement data, and the apparent thickness of the nonwoven fabric after compression and release is called A.
Next, the thickness of the measurement sample after the pressure treatment is measured at a pressure of 2.5 kPa in the same manner.
Finally, the deformation stroke of the nonwoven fabric is calculated using the following formula.
"Nonwoven fabric deformation stroke after compression and release [mm]" = A - B

Such a nonwoven fabric of the present invention can be realized by various structures in the nonwoven fabric. For example, the nonwoven fabric may have the following layers a to i.
a. Natural fiber layer b. Hollow fiber layer partially having embossed and compressed portions c. Core-sheath type composite fiber layer in which the core ratio is greater than the sheath ratio in the core-sheath mass ratio of the composite fiber d. Elastomer fiber layer e. Low elongation fiber layer f. Unfused fiber layer g. Layer in which multiple uneven nonwoven fabrics are laminated h. Layer with longitudinal fiber orientation i. Layer in which a binder exists at fiber intersections

These layers may be present in the entire nonwoven fabric of the present invention, or may be present in only a part of it. When present in only a part of it, these layers are preferably in the middle layer of the thickness of the nonwoven fabric. Also, it is preferable that these layers are present on the side opposite to the surface receiving the compressive force. For example, when the nonwoven fabric of the present invention is used as a top sheet of an absorbent article, the opposite side is the non-skin side. In addition, the nonwoven fabric of the present invention may have any one of the layers shown below, or may have more than one of them. When the nonwoven fabric of the present invention has more than one of the layers shown below, the multiple layers may be separate layers, or each of the layers may have a mixed structure within one layer.
The "middle layer of thickness" of the nonwoven fabric mentioned above means the "middle layer 50%" portion when the apparent thickness of the nonwoven fabric under a load of 50 Pa is defined as 25% upper layer, 50% middle layer, and 25% lower layer.

In particular, the layers a, d, f, and h are preferably intermediate layers within the above-mentioned thickness range.
It is preferable that the layers b, c, e and g constitute the entire nonwoven fabric.
The layer i preferably constitutes 70% of one side of the nonwoven fabric.

Below, the above items a to i will be explained in detail.
a. Natural fiber layer This layer is a layer using natural fibers, unlike thermoplastic fibers. The natural fibers referred to here are not particularly limited, but are preferably cellulose fibers, cotton, etc. For example, cellulose fibers are not thermally fused at the intersections between the fibers, and the fibers are relatively free to deform. It is preferable that the cellulose fibers are curled by being crimped or spirally formed.
The nonwoven fabric of the present invention has a high thickness recovery after compression due to the inclusion of a natural fiber layer. As such cellulose fibers, any cellulose fiber that is commonly used in this type of article can be used without any particular limitation. For example, those described in paragraphs [0098] and [0291] of JP-T-2017-526473 can be mentioned.
The method for constructing this layer as a nonwoven fabric is not particularly limited, but for example, natural fibers are mixed with thermoplastic fibers, or sandwiched between layers of thermoplastic fibers, and then the layers are made into a nonwoven fabric using a thermal bonding method such as fixing with an embossing roll or an air-through method, or a needle punch method or a spun lace method.

A layer of hollow fibers partially having embossed and crimped portions. The hollow fibers contain air inside, and the embossed and crimped portions trap the air in the hollow. This gives the hollow fibers the ability to recover from bending, like a tubular balloon.
The nonwoven fabric of the present invention has a layer of hollow fibers partially having such embossed and compressed portions, and thus has high thickness recovery after compression.
The method for forming this layer as a nonwoven fabric is not particularly limited, but for example, hollow fibers using a thermoplastic resin are used, and the fibers are compressed with an embossing roll or the like to form a nonwoven fabric.

c. A layer of fibers having a core-sheath type composite fiber, the core ratio of which is greater than the sheath ratio in terms of the core-sheath mass ratio of the composite fiber. Specifically, the above-mentioned core-sheath type composite fiber is a fiber containing two or more different resin components as constituent components. In the case where the glass transition temperature of the sheath resin component is lower than that of the core resin component with respect to this melting point (for example, the core resin component is PET and the sheath resin component is PE), the thickness recovery of the nonwoven fabric can be improved by reducing the mass ratio of the resin component with a lower glass transition temperature. The following factors are considered to be the cause of this. It is known that resins with a low glass transition temperature have a low relaxation modulus. It is also known that a low relaxation modulus makes it difficult to recover from deformation. Therefore, it is considered that a higher thickness recovery can be imparted to the nonwoven fabric by reducing the resin component with a low glass transition temperature as much as possible.
The core-sheath type composite fiber preferably has a configuration in which a core component and a sheath component are concentrically arranged.
"The core ratio is greater than the sheath ratio in the core-sheath mass ratio of the composite fiber" means that the mass ratio of the core component in the mass of the composite fiber is greater than the mass ratio of the sheath component in the mass of the composite fiber. As such a core-sheath type composite fiber, any fiber that is commonly used in this type of article can be used without any particular restrictions. For example, the fiber described in paragraph [0051] of JP 2019-44321 A can be used.
The above-mentioned core-sheath type composite fiber is a thermoplastic fiber, and is thermally fused to other fibers at their intersections to form fusion points.
The nonwoven fabric of the present invention has high thickness recovery after compression due to the inclusion of layers of the core-sheath type composite fibers as described above.
The method for forming this layer as a nonwoven fabric is not particularly limited, but it is preferable to use a thermal bonding method such as an air-through method.

(Method for identifying different resin components in core-sheath composite fibers)
Whether or not the composite fiber contains two or more types of resin components is judged from the melting point peak measured by the following method. Regarding the counting of endothermic peaks, if peaks appear at intervals of 5°C or more, it is judged that the resin components are different types.
(1) Prepare a 0.01 g nonwoven fabric sample as a measurement sample.
(2) Using a differential scanning calorimeter "DSC7000X" (product name, manufactured by Hitachi High-Tech Science Corporation), 0.01 g of a nonwoven fabric sample is weighed into an aluminum pan, heated to 200°C, and then cooled to 0°C at a rate of 10°C/min.
(3) The temperature is increased to 300° C. at a rate of 10° C./min, and the endothermic peak is measured.

(Method for measuring the mass ratio of the core component and the sheath component to the mass of a core-sheath type composite fiber)
The nonwoven fabric to be measured is cut to a size of 10 cm x 10 cm to prepare a measurement sample. If it is not possible to take out a piece of nonwoven fabric of a size of 10 cm x 10 cm, take out a piece of the fabric as large as possible.
The measurement sample is frozen with liquid nitrogen, and then the thickness cross section of the nonwoven fabric is cut with a razor blade so as to be perpendicular to the flow direction of the fibers when the nonwoven fabric is viewed in plan, to obtain a cross section of a core-sheath type composite fiber. The cross section of the composite fiber is observed at a magnification of 2000 times using a tabletop scanning electron microscope (SEM) JCM-6000Plus (trade name, manufactured by JEOL Ltd.; all SEMs used in this specification are of this type). The size of the observation screen is enlarged to 43 μm vertically and 60 μm horizontally.
The cross-sectional areas of the core and sheath components are measured, the volume per unit length is calculated, and the core-sheath ratio (mass ratio) is calculated from the density of each resin component. The average value of the measurement results for 10 fibers is used as the measurement data for the core-sheath ratio. The density of the resin component is the value from the Plastic Materials Directory (Processing Technology Research Association).

d. Elastomer fiber layer The nonwoven fabric of the present invention has a layer of elastic elastomeric fibers, which enhances the thickness recovery after compression. The term "elastomer" as used herein is defined as a material that does not break brittle when stretched and has elasticity. The elastomeric fiber may be any commonly used fiber without any particular limitations, and examples of such fibers include the thermoplastic elastomer fibers described in paragraphs [0010] to [0060] of JP 2007-321293 A.
The method for constructing this layer as a nonwoven fabric is not particularly limited, but for example, an elastomer fiber using a thermoplastic resin is used, or a thermoplastic elastomer fiber is mixed with a thermoplastic fiber, or the layer is sandwiched between layers of thermoplastic fiber, and then the nonwoven fabric is formed using a thermal bonding method such as fixing with an embossing roll or an air-through method, or a needle punch method or a spun lace method.

e. Layer of low elongation fiber The low elongation fiber refers to a fiber having an elongation (breaking elongation) of 100% or less, measured in accordance with JIS L1015 7.7.1.
The thickness recovery of the nonwoven fabric of the present invention is further improved by the presence of the low elongation fiber in the above-mentioned "c. A layer of fibers which are sheath-core composite fibers and in which the core ratio is greater than the sheath ratio in terms of the core-sheath mass ratio of the composite fiber." Also, in the nonwoven fabric of the present invention, the "e. A layer of low elongation fibers" is more dominant in terms of thickness recovery than the above-mentioned "c. A layer of fibers which are sheath-core composite fibers and in which the core ratio is greater than the sheath ratio in terms of the core-sheath mass ratio of the composite fiber."
Such low elongation fibers are difficult to elongate and therefore undergo little change in shape.
Therefore, the nonwoven fabric of the present invention has high thickness recovery after compression by including a layer of low elongation fibers. From this viewpoint, the elongation of the low elongation fibers is more preferably 90% or less, and even more preferably 85% or less.
The elongation of the low elongation fiber is preferably 40% or more, more preferably 50% or more, and even more preferably 60% or more, from the viewpoint of strengthening the fusion between the fibers and increasing the strength of the nonwoven fabric.
The method for forming this layer into a nonwoven fabric is not particularly limited, but for example, the nonwoven fabric may be formed by a thermal bonding method such as fixing with an embossing roll or an air-through method, or by a needle punch method or a spun lace method.

f. Unfused fiber layer An unfused fiber layer is a layer in which the intersections of fibers are not bonded together. Specifically, it is a layer that is not thermally fused by thermoplastic fibers. It is also a layer that is not bonded or mechanically bonded by a binder.
The fibers of such layers are preferably made of a high melting point resin.
In the unfused fibrous layer, the fibers are relatively free to deform, and therefore, the nonwoven fabric of the present invention has high thickness recovery after compression by including the unfused fibrous layer.
From this viewpoint, it is preferable that the unfused fiber layer has the above-mentioned intermediate thickness layer.
The method for constructing this layer as a nonwoven fabric is not particularly limited, but for example, fibers made of a high melting point resin are mixed with thermoplastic fibers and the nonwoven fabric is formed using a needle punching method or a spun lace method, or a thermal bonding method in which the fibers made of a high melting point resin are sandwiched between layers of thermoplastic fibers and fixed using an embossing roll or an air-through method, or a needle punching method or a spun lace method is used to form a nonwoven fabric.

g. Layer of multiple uneven nonwoven fabrics stacked on top of each other By facing the convex part of one uneven nonwoven fabric to one side and the convex part of the other uneven nonwoven fabric to the opposite side, the bottoms of the concave parts of each nonwoven fabric are joined together, so that the concave parts support each other's uneven structure while maintaining the thickness. This improves the shape retention of the layer of uneven nonwoven fabrics stacked on top of each other. In addition, the spaces in the concave parts of each uneven nonwoven fabric increase the flexibility of the layer of uneven nonwoven fabrics stacked on top of each other, improving the soft feel and cushioning. A specific example of such a layer of uneven nonwoven fabrics stacked on top of each other is shown in FIG. 1 of JP 2013-194333 A.
In addition, as a method for laminating the uneven nonwoven fabrics together, various methods that can be usually used can be adopted without any particular restrictions. For example, embossing, heat fusion by hot air treatment, and bonding by hot melt adhesive can be mentioned. From the viewpoint of maintaining a soft texture, heat fusion by hot air treatment and bonding by hot melt adhesive are preferable to embossing.
The number of layers of the uneven nonwoven fabric is not limited to two, but may be three or more. In the case of three or more layers, an additional layer may be laminated between one side and the opposite side.
The nonwoven fabric of the present invention has a layer in which a plurality of such uneven nonwoven fabrics are laminated, and thus has excellent shape retention, flexibility, softness to the touch and cushioning properties, and has high thickness recovery after compression.

h. Layer with longitudinal fiber orientation The longitudinal fiber orientation refers to the fibers being oriented in the thickness direction of the nonwoven fabric. As mentioned above, the thickness direction refers to the vertical direction to the horizontal plane when one side of the nonwoven fabric is placed on the horizontal plane. Examples of layers with longitudinal fiber orientation include those described in paragraphs [0005] to [0026] of JP-A-5-263345.
A layer having longitudinally oriented fibers is less likely to collapse even when subjected to a compressive force in the thickness direction, and has high shape recovery properties.
Therefore, the nonwoven fabric of the present invention has a layer having such longitudinal fiber orientation, and thus has high thickness recovery after compression. In particular, the deformation stroke of the nonwoven fabric after release from compression can be improved.
From this viewpoint, it is preferable that the layer having longitudinally oriented fibers is present at least in the intermediate thickness layer portion of the nonwoven fabric of the present invention.
The method for forming this layer into a nonwoven fabric is not particularly limited, but it is preferable to form the nonwoven fabric using a thermal bonding method in which thermoplastic fibers are fixed using an embossing roll or air-through method, or a needle punch method or a spun lace method.

The longitudinal orientation of the fibers is indicated by the degree of longitudinal orientation of the fibers. The "degree of longitudinal orientation" is a value measured by the method described below (Method for measuring the degree of longitudinal orientation of fibers), and indicates the degree to which the orientation of fibers having a thickness direction component is uniform.
The term "fibers having a thickness direction component" refers to fibers that have a vertical component as a vector relative to a horizontal plane when the nonwoven fabric of the present invention is placed on a horizontal plane with one of the front and back sides facing up. In this specification, "thickness direction" means that the vertical component is greater than zero. Also, "fibers having a thickness direction component" is synonymous with "longitudinal oriented fibers."

From the viewpoint of improving the thickness recovery property of the nonwoven fabric after compression, the degree of longitudinal orientation is preferably 55% or more, more preferably 60% or more, and even more preferably 65% or more.
From the viewpoint of increasing the strength of the nonwoven fabric, the degree of longitudinal orientation is preferably 95% or less, more preferably 90% or less, and even more preferably 80% or less.

(Method of measuring the degree of longitudinal orientation of fibers)
(1) A nonwoven fabric sample is frozen with liquid nitrogen and placed on a horizontal surface, and then a thickness cross section (cross section in the vertical direction) of a portion of the nonwoven fabric sample that is 50% of the thickness in the vertical direction relative to the horizontal surface (the thickness center portion) is cut with a razor blade to prepare a thickness cross section.
(2) The thickness cross section is observed at 35 times magnification using a SEM, and an observed image is taken.
(3) A reference line L forming a square of 0.5 mm x 0.5 mm (dimensions within the observed image) is added to the observed image. Here, the reference line L is composed of an upper side L1 and a lower side L2 that are aligned in a direction along the horizontal plane, and a left side L3 and a right side L4 that are aligned in the vertical direction.
(4) Count the total number of fibers passing through the reference lines formed by each side of the square. The total number of fibers passing through the reference lines L of the top and bottom sides L1 and L2 of the square is the "top and bottom fiber number," and the total number of fibers passing through the reference lines L of the left and right sides L3 and L4 of the square is the "left and right fiber number."
(5) The degree of longitudinal orientation Q of the fibers of a nonwoven fabric is calculated as (number of upper and lower fibers)/(number of upper and lower fibers + number of left and right fibers)×100.
Three observation images of each of these points are prepared and measured for the same nonwoven fabric sample, and the average is used as the measurement data.
1 shows an observation screen with a square reference line L. In the figure, black dots 71 indicate positions where the fiber 7 passes through the reference line L (L1 to L4).

The "thickness center" means a portion between a horizontal plane and an imaginary plane in the "apparent thickness" of the nonwoven fabric defined above, the portion being 50% of the distance in the vertical direction to the horizontal plane.
The thickness of the nonwoven fabric here is measured based on the above-mentioned (method of measuring the apparent thickness of a nonwoven fabric under a load of 50 Pa).

i. Layer with binder at fiber intersections Fiber intersections refer to the areas where two or more fibers cross. The binder at the fiber intersections preferably covers the outer surface of the area where the fibers cross and overlap. In addition, the binder is preferably present at the fiber intersections while extending to the fiber surface other than the fiber intersections.
It is also preferred that the binder is present at fiber intersections in the thickness center of the nonwoven fabric of the present invention, i.e., the layer in which the binder is present at the fiber intersections is preferably located in the thickness center of the nonwoven fabric of the present invention.

In the nonwoven fabric of the present invention, which contains thermoplastic fibers and has fusion points between fibers, the binder acts to restore the three-dimensional intersections between fibers by providing a layer having a binder at the fiber intersections. That is, when a compressive force (pressing force) is applied to the nonwoven fabric of the present invention from one side, the three-dimensional intersections of the fibers at the fiber intersections are crushed by the compressive force. However, when the compressive force is removed, the binder restores the arrangement of the three-dimensional intersections of the fibers at the fiber intersections.
The nonwoven fabric of the present invention has high thickness recovery after compression due to the above-mentioned effect in the layer in which the binder is present at the fiber intersections.

Such binders have a viscosity or adhesiveness that allows them to adhere to the surface of fiber intersections and not run off. In addition, the binder has a softness that ensures the mobility of the fibers at the fiber intersections, which is necessary for the cushioning properties of the nonwoven fabric, while also having a viscosity or adhesiveness that allows the positional relationship between the fibers to return to their original position after movement. Furthermore, in view of the above-mentioned effects, it is preferable for the binder to have elasticity.

Various binders can be used, such as acrylic resins, ester resins, vinyl acetate resins, styrene resins, vinyl acetate-ethylene resins, and styrene-butadiene rubber.
In particular, acrylic resins, styrene-butadiene rubber, and the like are preferred as they have the viscosity, adhesiveness, and softness to restore the three-dimensional intersection of fibers at the fiber intersections.

(Method for checking the presence or absence of binder at fiber intersections in the center of nonwoven fabric thickness)
(1) Prepare a 0.3 g nonwoven fabric sample as a measurement sample. Next, place the nonwoven fabric sample in a beaker containing 100 mL of ethyl acetate and stir for 30 minutes. Remove the nonwoven fabric sample and dry it. This washes away any components attached to the nonwoven fabric sample, such as skin care agents and hot melt adhesives.
(2) The nonwoven fabric sample is dyed using an identification reagent (fiber identification reagent Bouken Stain II, manufactured by Bouken Quality Evaluation Organization, a general incorporated foundation) that dyes the binder fixed to the fiber surface a color different from the fiber to distinguish between the two.
(3) A nonwoven fabric sample is frozen with liquid nitrogen, and then cut with a razor blade to prepare two cross sections passing through the center of the thickness of the nonwoven fabric sample. One is cross section A passing through the center of the thickness of the nonwoven fabric sample (a cross section passing through the center of the thickness and perpendicular to the fiber layer forming the nonwoven fabric surface), and the other is cross section B passing through the center of the thickness of the nonwoven fabric sample and perpendicular to cross section A.
The cross section may be any of a cross section along the MD (Machine Direction) direction (machine flow direction in the manufacturing process) in the plane of the nonwoven fabric, a cross section along the CD (Cross Direction) direction (direction perpendicular to the machine flow direction), and any cross section therebetween. It is sufficient that a cross section passing through the thickness center along at least one of the planar directions satisfies the predetermined requirements.
(4) The sample prepared in (3) above is placed on a horizontal surface with the cross section facing upward. In this state, an observation image is taken at 100x magnification using a digital microscope VHX-900 (product name, manufactured by Keyence Corporation).
(5) For the observation images of the above two cross sections, a reference circle C with a diameter of 1.0 mm (dimensions within the observation image) is drawn within the observation image. The number of fiber intersections (N) within the reference circle C and the number of dyed fiber intersections (Nb) among the number of fiber intersections (N) are counted. As a result of the counting, the cross section with the larger number of dyed fiber intersections (Nb) is the measurement target. (The range in focus in the observation image is the measurement target.)
Fiber intersections are counted both where the fibers are fused and where they are not fused.
When obtaining an observation image of the thickness center portion of cross section A, the cross section sample is adjusted to the center of the observation screen from a low magnification, and the thickness center portion is identified by increasing the magnification.
(6) Next, the presence rate of the binder on fiber intersections per unit area at the center of the thickness of the nonwoven fabric is calculated based on the following formula (S1).
H (%) = Nb÷N×100 (S1)
H: Presence rate of binder on fiber intersections per unit area
Nb: Number of dyed fiber intersections within the reference circle C
N: Number of fiber intersections within the reference circle C (including Nb)
For each of these, three points are observed on the same nonwoven fabric sample, and two observation images are prepared and measured. The larger value of the measurement result of the binder presence rate on the fiber intersections of cross sections A and B is adopted, and the average is used as the measurement data.
FIG. 2 shows that a plurality of fiber intersections 6 where fibers 7 intersect with each other, and dyed fiber intersections 61, are present within a reference circle C marked on the observation screen.

The two cross sections A and B in (3) above are, for example, as follows.
When the nonwoven fabric has a flat shape with no unevenness in the fiber layers that are continuous in both the planar and thickness directions, cross section A is a cross section that passes through the thickness center and is perpendicular to the fiber layers that form the nonwoven fabric surface (plane). In this case, cross section B is a cross section that passes through the thickness center and along the nonwoven fabric plane. Specifically, cross section A is a cross section taken along a vertical line A-A that passes through the thickness center 105 of the nonwoven fabric 100S as shown in Fig. 3(A). Cross section B is a cross section taken along a horizontal line B-B at the thickness center 105 of the nonwoven fabric 100S as shown in Fig. 3(B).
In addition, when the fiber layer of the nonwoven fabric meanders in the thickness direction to have an uneven shape with alternating convex and concave portions, cross section A is a cross section that passes through the thickness center and is perpendicular to the fiber layer that forms the nonwoven fabric surface (the wall surface connecting the top of the convex portion and the bottom of the concave portion). In this case, cross section B is a cross section along the fiber layer that passes through the thickness center and forms the nonwoven fabric surface (the wall surface connecting the top of the convex portion and the bottom of the concave portion). Specifically, cross section A is a cross section along line A-A that passes through the thickness center 105 of the nonwoven fabric 100W as shown in FIG. 4(A). Cross section B is a cross section along line B-B (a line perpendicular to line A-A) at the position of the thickness center 105 of the nonwoven fabric 100W as shown in FIG. 4(B).

The dyeing process (2) above will now be described.
(2-1) Shake the container of Bouken Stain II well to mix thoroughly.
(2-2) Place 1.5 mL of the mixed Bouken Stain nII in a beaker of approximately 200 mL size, add deionized water, and make the dye solution to a total volume of 30 mL.
(2-3) The dye solution is heated, and when the temperature is about 90°C before boiling, the nonwoven fabric sample is added and boiled at 95°C for 2 minutes.
(2-4) The nonwoven fabric sample is taken out, thoroughly washed with water, and then dried.
(2-5) The color is compared with the identification color and judged. For example, a binder containing acrylic resin or styrene-butadiene rubber will be dyed red and the fiber will remain white (however, the dyeing of the binder will differ depending on the binder components).

The binder is a resin component different from the constituent fibers of the nonwoven fabric, and is fixed to the surface of the constituent fibers after the nonwoven fabric is formed.
For example, the binder is sprayed onto one side of the nonwoven fabric by a spray or the like to adhere to the fiber intersections. The binder is preferably sprayed from the side of the nonwoven fabric opposite to the side that comes into contact with the skin, from the viewpoint of suppressing a sticky feeling when the nonwoven fabric comes into contact with the skin.
From the same viewpoint, the sprayed mass of the binder is preferably 5 g/m ² or less per unit area of the nonwoven fabric.
In order to effectively exert the action of the binder on the fiber intersections, the mass of the binder sprayed per unit area of the nonwoven fabric is preferably 0.3 g/m ² or more.

In the nonwoven fabric of the present invention, from the viewpoint of effectively exerting the action of the binder, the proportion of the mass of the binder in the mass of the nonwoven fabric is preferably 1% or more.
In the nonwoven fabric of the present invention, from the viewpoint of realizing a fluffy feel, the proportion of the mass of the binder in the mass of the nonwoven fabric is preferably 15% or less.

(Method for measuring the proportion of binder mass to nonwoven fabric mass)
(1) A total of 1.0 g of a nonwoven fabric sample is prepared by carrying out the same process as in (1) above (Method for confirming the presence or absence of binder at fiber intersections in the thickness center of a nonwoven fabric).
(2) Cut the nonwoven fabric sample into small pieces of 0.1 mm square. Place 1.0 g of the small pieces in a beaker and add hexafluoroisopropanol (hereinafter, also referred to as HFIP) to separate the sample into HFIP-insoluble and HFIP-soluble portions. This dissolves the PET component of the fiber.
(3) Add heated xylene at 130° C. to the HFIP insoluble fraction obtained in (2) above, thoroughly stir, and filter to separate into heated xylene insoluble fraction and heated xylene soluble fraction, thereby dissolving the PP and PE components of the fibers.
(4) The HFIP insoluble and heated xylene insoluble fractions obtained in (3) above are weighed and subjected to TG/DTA measurement. The amount burned in the TG/DTA measurement is defined as the binder mass (the fibers may contain additives such as titanium oxide. If the fibers contain titanium oxide, this allows the binder and titanium oxide to be separated).
(5) The binder mass obtained in (4) above is divided by 1.0 g of the nonwoven fabric sample prepared in (1) above to calculate the binder mass percentage.

In the above (method of measuring the proportion of binder mass in nonwoven fabric material), regardless of the surface to which the binder is sprayed, the amount of binder adhered to the entire nonwoven fabric can be understood as a mass proportion of the nonwoven fabric mass relative to the fibers.

The binder may be present at other fiber intersections as well, so long as it is present at the fiber intersections in the thickness center of the nonwoven fabric. The fiber intersections where the binder is present may be fused fibers or may be intersections of non-fused fibers.
Since the binder has adhesiveness, a small amount of the binder can exert the above-mentioned effect. Therefore, the fiber intersection where the binder is present is preferably a fusion point between fibers. Compared to the intersection of non-fused fibers, the fusion point already forms a bonded intersection, so it is not necessary to form an intersection by the binder. As a result, a small amount of binder is required for thickness recovery at the fusion point between fibers compared to the non-fused fiber intersection, and the thickness recovery effect due to the elasticity of the binder can be prevented from being reduced by the adhesiveness of the binder.
When the binder is present at the fusion points between the fibers, the positional relationship (multi-level crossing relationship) between the fixed fibers can be more firmly maintained.
Furthermore, when the binder is present at the intersections between non-fused fibers, the positional relationship between the fibers (three-dimensional intersection relationship) can be restored while maintaining soft deformability when pressed.
From the viewpoint of achieving both thickness recovery and soft cushioning of the nonwoven fabric, it is preferable that the binder is present at both the fusion points between fibers and the intersections between non-fused fibers. In this case, it is preferable that the number of fiber intersections at the center of the thickness of the nonwoven fabric where the binder is present is greater than the number of fused fiber intersections.

The nonwoven fabric of the present invention is preferably made of thermoplastic fibers. For example, it is preferably composed of the layers b to i described above. This facilitates the fabric to return to its original shape starting from the fusion points between the fibers, further improving recovery and cushioning properties.

The nonwoven fabric of the present invention is preferably made of the composite fiber described above in "c. A layer of fibers that is a core-sheath type composite fiber and has a core-sheath mass ratio that is greater than the sheath ratio" among thermoplastic fibers. Specifically, the nonwoven fabric of the present invention is preferably made of composite fibers that contain two or more different resin components, and the core-sheath mass ratio of the composite fiber is preferably such that the core ratio is greater than the sheath ratio.

Furthermore, in the nonwoven fabric of the present invention, the composite fiber is preferably a low elongation fiber as shown in "e. Layer of low elongation fiber" rather than an elastomeric fiber as shown in "d. Layer of elastomeric fiber" above. In other words, the elongation of the composite fiber is preferably 100% or less, and more preferably within the range shown in "e. Layer of low elongation fiber" above. This suppresses deformation caused by the weight and minute pressure generated by the elastomeric fiber, making the effect of recovery more likely to be observed.

In addition, it is preferable that the nonwoven fabric of the present invention has fusion points between the fibers in the center of the thickness. For example, it is preferable that the nonwoven fabric has the aforementioned layers b to e and g to i in the center of the thickness. This prevents the fibers from becoming biased due to compression in the center of the thickness, and allows the restoring force originating from the fusion points between the fibers to be exerted uniformly within the layer, preventing unevenness in recovery and cushioning properties.

The definition of the "center part of the thickness" and the method for measuring the thickness are as described above. The above fusion points can be confirmed by the following method.

(Method for checking the presence or absence of fusion points between fibers in the center of the thickness of a nonwoven fabric)
(1) Cut the nonwoven fabric to be measured into a size of 10 cm x 10 cm to prepare a nonwoven fabric sample. If it is not possible to take out a piece of nonwoven fabric of a size of 10 cm x 10 cm to be measured, take out a piece of the fabric as large as possible.
(2) The same processes as those in (1) and (2) of the above (Method for measuring the degree of longitudinal orientation of fibers) are carried out to obtain an observation image of the thickness center of the nonwoven fabric sample. At that time, the cross-sectional sample is adjusted to the center of the observation screen from a low magnification, and the thickness center is identified by increasing the magnification.
(3) A reference circle with a diameter of 0.5 mm (a dimension within the observed image) is drawn within the observed image, and the number of fusions between fibers within the circle is counted to determine whether or not there are fusion points (the range in focus in the observed image is the measurement target). The number of fusion points is also counted, and these are measured by preparing and measuring three observation images of each sample, and the average is used as the measurement data for the number of fusion points per unit area.

In the nonwoven fabric of the present invention, the number of fusion points per unit area at the center of the thickness is preferably 100/mm2 ^{or more} , more preferably 120/mm2 ^{or more} , and even more preferably 150/mm2 or ^more , from the viewpoint of the strength of the nonwoven fabric.
In addition, the number of fusion points per unit area at the center of the thickness is preferably 300/mm2 or ^less , more preferably 250/mm2 ^{or less} , and even more preferably 220/mm2 or ^less , from the viewpoint of imparting a soft feel to the nonwoven fabric.

In addition, in the nonwoven fabric of the present invention, from the viewpoint of fluffy texture, the smaller the area of the embossed part (hereinafter also referred to as the embossed part) as shown in the above-mentioned "g. Layer in which a plurality of uneven nonwoven fabrics are laminated" is, the better. Therefore, the embossing rate measured by the following method is preferably 15% or less, more preferably 10% or less, and even more preferably 5% or less.
The lower limit of the embossing rate is not particularly set, but is 0% or more.

(Method of measuring embossing rate)
(1) Select the part of the nonwoven fabric sample with the highest embossing rate, and cut the nonwoven fabric to be measured into a size of 10 cm x 10 cm to prepare a measurement sample. If it is not possible to take out a size of 10 cm x 10 cm as the nonwoven fabric to be measured, take out a size as large as possible.
(2) The nonwoven fabric is placed horizontally and an observation image is taken. The area ratio of the film-formed portion in a 50 mm x 50 mm square of the observation image is measured as the embossing ratio. Three observation images are prepared and measured for each of the same sample, and the average is used as the measurement value data. The film-formed portion refers to a surface that does not have irregularities larger than the fiber diameter, a surface formed with irregularities equal to or smaller than the fiber diameter, or a flat surface that does not have irregularities equal to or smaller than the fiber diameter.

The nonwoven fabric of the present invention preferably has an uneven shape at the above embossing rate. This uneven shape is preferably present on at least one side of the nonwoven fabric of the present invention and on the opposite side, and more preferably on both sides. This makes it easier for the embossed portion to retain space, further improving recovery and cushioning properties.

Furthermore, the nonwoven fabric of the present invention preferably has a degree of longitudinal orientation of fibers in the range of values shown in the above-mentioned "h. Layer having longitudinal orientation of fibers". It is preferable that the nonwoven fabric of the present invention has such a degree of longitudinal orientation of fibers at least in the intermediate layer.
In the nonwoven fabric of the present invention, as described above in "i. Layer in which a binder is present at fiber intersections", it is preferable that the binder is present at fiber intersections in the thickness center. It is also preferable that the proportion of the mass of the binder in the mass of the nonwoven fabric of the present invention is within the range described above in "i. Layer in which a binder is present at fiber intersections".

The nonwoven fabric of the present invention has a bulkiness due to the apparent thickness of the nonwoven fabric under a load of 50 Pa as described above, and from the viewpoint of having excellent compression characteristics and a fluffy texture, the basis weight is preferably 100 g/m2 or ^less , more preferably 60 g/m2 or ^less , and even more preferably 40 g/m2 or ^less .
In addition, the lower limit of the basis weight is not particularly limited, but from the viewpoint of improving the texture of the nonwoven fabric, it is preferably 8 g/m2 or ^more , more preferably 10 g/m2 or ^more , and even more preferably 15 g/m2 or ^more .

While having the above-mentioned configuration, the nonwoven fabric of the present invention preferably has an uneven shape that includes convex portions, concave portions, and walls connecting the convex portions and the concave portions in the thickness direction of the nonwoven fabric. By making the uneven shape, the nonwoven fabric of the present invention becomes bulkier (thicker) and has a good feel while keeping the basis weight low. This allows the nonwoven fabric of the present invention to have a fluffy feel due to the compression characteristics described above, i.e., excellent cushioning properties.

When the nonwoven fabric of the present invention 1 has an uneven shape, various uneven shapes can be used. In addition, various materials that are usually used as materials that come into contact with the skin can be used.
For example, the uneven shape of the nonwoven fabric may be of various types, such as those with solid convexities, those with hollow convexities, those with a single fiber layer, those with a two-layer fiber layer, those with convexities arranged in a scattered manner in the planar direction, those with convexities and concaves arranged in a ridge-like pattern, etc. In addition, the uneven shape is not limited to being on one side, and may be on both sides.
Among these, preferred is a nonwoven fabric having a single layer structure in which the convex portions of the concave-convex shape are hollow and the concave-convex shape is present on both sides of the nonwoven fabric, for example, the following nonwoven fabric 80 (specific example 1) and nonwoven fabric 90 (specific example 2).
These are explained below.

The nonwoven fabric 80 (Specific Example 1) has a layer structure containing thermoplastic fibers and has the following uneven shape. The nonwoven fabric 80 also satisfies the above-mentioned requirements of (h. Layer having longitudinal fiber orientation) and (i. Layer having binder at fiber intersections).
That is, it has outer fiber layers 81, 82 on the first surface (one surface) 1A side and the second surface (opposite surface) 1B side, and a plurality of connecting portions 83 disposed between the outer fiber layer 1 on the first surface 1A side and the outer fiber layer 2 on the second surface 1B side. The outer fiber layer 81 on the first surface 1A side and the outer fiber layer 82 on the second surface 1B side and the connecting portions 83 are partially fused to each other by fibers.
In addition, in the outer fiber layer 82 and the connecting portion 83 on the second surface 1B side, the binder is present at the fiber entanglement points, and the binder is attached so as to cover the fiber entanglement points.
The outer fiber layers 81, 82 and the connecting portion 83 form an uneven shape in the thickness direction of the nonwoven fabric 80, which includes hollow convex portions, concave portions, and walls connecting the convex portions and the concave portions. The uneven shape is formed on both the first surface 1A side and the second surface 1B side. Specifically, on the first surface 1A side, the convex portions 81 formed by the outer fiber layer 81 and the concave portions 88 between the outer fiber layers 81 have an uneven shape. On the second surface 1B side, the convex portions 82 formed by the outer fiber layer 82 and the concave portions 89 between the outer fiber layers 82 have an uneven shape. Both the convex portions 81 formed by the outer fiber layer 81 and the convex portions 82 formed by the outer fiber layer 82 are hollow. The connecting portion 83 forms a wall portion 83 connecting the convex portions 81 and the concave portions 88 (the convex portions 82 and the concave portions 89).
The nonwoven fabric 80 may have various configurations described in paragraphs [0010] to [0048] of JP 2019-44319 A. For example, the uneven shape of the nonwoven fabric 80 may be a shape in which the convex portions 81 formed by the outer surface fiber layer 81 and the concave portions 88 between them are arranged in a ridge-like shape on the first surface 1A side. Similarly, the convex portions 82 formed by the outer surface fiber layer 82 and the concave portions 89 between them may be arranged in a ridge-like shape on the second surface 1B side. In addition, the outer surface fiber layers 81 and 82 may have fibers oriented in the planar direction. The wall portion 83 formed by the connecting portion 83 may have fibers oriented vertically. The outer surface fiber layer 1 that becomes the convex portion on the first surface 1A side may have two types (a first outer surface fiber layer 81A and a second outer surface fiber layer 81B) having lengths extending along different directions that intersect in a plan view of the nonwoven fabric. The multiple connecting parts 83 may be arranged along different directions that intersect in a plan view of the nonwoven fabric, and may have two types (first connecting parts 83A and second connecting parts 83B) with different wall surface orientations of the connecting parts 83. In this case, the first connecting parts 83A and the second connecting parts 83B may have wall surface orientations that are different from each other, or the fibers may be oriented vertically.
This nonwoven fabric 80 typically has the shape shown in FIG.
Such a nonwoven fabric 80 can be manufactured by the method described in paragraphs [0049] to [0057] of JP 2019-44319 A.

The nonwoven fabric 90 (Specific Example 2) has a single layer structure containing thermoplastic fibers and has the following uneven shape. The nonwoven fabric 90 satisfies the above-mentioned requirements of (h. Layer having longitudinal fiber orientation) and (i. Layer having binder at fiber intersections).
That is, on the first surface (one surface) 1A side, a plurality of vertical ridges 911 protruding toward the first surface 1A side in the thickness direction of the nonwoven fabric are arranged extending in one direction on the first surface 1A side in a plan view. The vertical ridges 911 are arranged side by side at a distance in another direction on the first surface 1A side in a plan view different from the one direction on the first surface 1A side. In addition, horizontal ridges 921 extending in the other direction on the first surface 1A side are arranged connecting the vertical ridges 911. The vertical ridges 911 and the horizontal ridges 921 each form a hollow convex portion. The nonwoven fabric 90 has an uneven shape in its thickness direction, which includes convex portions, concave portions, and wall portions 911W connecting the convex portions and the concave portions, by the vertical ridges 911 and the horizontal ridges 921 and the concave portions 922 between them. On the first surface 1A side, the convex portions formed by the vertical ridge portions 911 and the horizontal ridge portions 921 have lengths extending along different directions that intersect in a plan view of the nonwoven fabric 90. In this case, the uneven shape on the first surface side of the nonwoven fabric 90 may be a shape in which the convex portions formed by the vertical ridge portions 911 and the horizontal ridge portions 921 and the concave portions therebetween are arranged in a ridge-groove shape.
In addition, on the second surface (opposite surface) 1B side, a plurality of hollow convex streaks 931 are arranged, which extend in one direction on the second surface 1B side in plan view and are arranged in another direction on the second surface 1B side different from the one direction on the second surface 1B side. In addition, a concave streaks 936 sandwiched between the plurality of convex streaks 931 extends in one direction on the second surface 1B side. The uneven shape on the second surface 1B side of the nonwoven fabric 90 has a shape in which the convex streaks 931 and the concave streaks 936 are arranged in a ridge-like shape. The convex streaks 931 are formed by a plurality of convex portions 934 connected in a ridge-like shape, and narrow and wide portions are alternately connected and arranged in a plan view. Between the convex portions 934 connected in a ridge-like shape, there is a slightly low depression 935. The nonwoven fabric 90 has an uneven shape in its thickness direction, which includes protrusions, recesses, and walls 931W connecting the protrusions and recesses, formed by the protrusions 931 and the recesses 936.
Furthermore, in the convex rib portion 931, the concave rib portion 936, and the wall portion 931W, the binder is present at the fiber entanglement points, and is adhered so as to cover the fiber entanglement points.
The nonwoven fabric 90 may employ various configurations described in paragraphs [0012] to [0058] of JP 2019-44320 A. For example, the orientation direction of the fibers constituting the vertical ridge portion 911 and the fibers constituting the horizontal ridge portion 921 may be different. The height of the vertical ridge portion 911 and the height of the horizontal ridge portion 912 may be different, and the horizontal ridge portion 921 may be curved in the thickness direction of the nonwoven fabric 90 or may have an equal height. In addition, each of the two lines constituting the widthwise outline of the convex strip portion 931 when viewed in plan from the second surface 1B side may be a curve having multiple arcs. Fuzz may be arranged on the side of the convex strip portion 931.
The nonwoven fabric 90 typically has the shape shown in Figures 6-11.
Such nonwoven fabric 90 can be produced by the method described in paragraphs [0059] to [0065] of JP 2019-44320 A.

Such a nonwoven fabric of the present invention can be used for various purposes.
For example, the nonwoven fabric of the present invention can be used in absorbent articles such as diapers, sanitary napkins, panty liners, and urine pads. Absorbent articles typically have a liquid-permeable top sheet, a back sheet, and an absorbent sandwiched between them. The nonwoven fabric of the present invention can be particularly suitably used as a top sheet. Furthermore, the nonwoven fabric can also be used as a sheet in the gather part, an exterior sheet, or a sheet in the wing part of an absorbent article.
The nonwoven fabric of the present invention can also be used as a component of an eye mask or a mask.

In relation to the above-described embodiments, the present invention further discloses the following nonwoven fabric and absorbent article.

＜1＞
A nonwoven fabric containing thermoplastic fibers and having fusion points between the fibers,
The apparent thickness of the nonwoven fabric under a load of 50 Pa is 4 mm or more,
The apparent thickness of the nonwoven fabric when pressed at 2.5 kPa is half or less of the apparent thickness of the nonwoven fabric when pressed at 50 Pa,
A nonwoven fabric, the values obtained by the following (method of measuring the apparent thickness and thickness recovery rate of a nonwoven fabric after releasing from compression) satisfy either or both of the following requirements (1) and (2).
(1) The recovery rate of the apparent thickness of the nonwoven fabric after release from compression is 40% or more.
(2) The apparent thickness of the nonwoven fabric after compression and release is 2 mm or more and 8 mm or less.
(Method of measuring apparent thickness and thickness recovery rate of nonwoven fabric after releasing from compression)
(a) "Nonwoven fabric apparent thickness before compression": a load of 50 Pa is applied to a nonwoven fabric sample to measure its apparent thickness.
(b) Next, the nonwoven fabric of the measurement sample is compressed to 0.7 mm under a load of 20 kPa. This compressed state is maintained in an atmosphere at 50° C. for 24 hours, and then the compressed state is released and the sample is left in an atmosphere at 25° C. for 30 minutes.
(c) Then, a laser thickness gauge is used to measure the thickness under a load of 50 Pa. Measurements are taken at three locations, and the average value is taken as the measurement data to obtain the "apparent thickness of the nonwoven fabric after release from compression."
(d) Finally, the recovery rate of the nonwoven fabric apparent thickness is calculated using the following formula.
"Recovery rate of apparent thickness of nonwoven fabric after release from compression [%]"
= "apparent thickness of nonwoven fabric after compression and release" ÷ "apparent thickness of nonwoven fabric before compression" × 100

＜2＞
A nonwoven fabric containing thermoplastic fibers and having fusion points between the fibers,
The apparent thickness of the nonwoven fabric under a load of 50 Pa is 4 mm or more,
The apparent thickness of the nonwoven fabric when pressed at 2.5 kPa is half or less of the apparent thickness of the nonwoven fabric when pressed at 50 Pa,
A nonwoven fabric, the values obtained by the following (method of measuring the apparent thickness and thickness recovery rate of a nonwoven fabric after release from compression) satisfy the following requirement (1).
(1) The recovery rate of the apparent thickness of the nonwoven fabric after release from compression is 40% or more.
(Method of measuring apparent thickness and thickness recovery rate of nonwoven fabric after releasing from compression)
(a) "Nonwoven fabric apparent thickness before compression": a load of 50 Pa is applied to a nonwoven fabric sample to measure its apparent thickness.
(b) Next, the nonwoven fabric of the measurement sample is compressed to 0.7 mm under a load of 20 kPa. This compressed state is maintained in an atmosphere at 50° C. for 24 hours, and then the compressed state is released and the sample is left in an atmosphere at 25° C. for 30 minutes.
(c) Then, a laser thickness gauge is used to measure the thickness under a load of 50 Pa. Measurements are taken at three locations, and the average value is taken as the measurement data to obtain the "apparent thickness of the nonwoven fabric after release from compression."
(d) Finally, the recovery rate of the nonwoven fabric apparent thickness is calculated using the following formula.
"Recovery rate of apparent thickness of nonwoven fabric after release from compression [%]"
= "apparent thickness of nonwoven fabric after compression and release" ÷ "apparent thickness of nonwoven fabric before compression" × 100

＜3＞
A nonwoven fabric containing thermoplastic fibers and having fusion points between the fibers,
The apparent thickness of the nonwoven fabric under a load of 50 Pa is 4 mm or more,
The apparent thickness of the nonwoven fabric when pressed at 2.5 kPa is half or less of the apparent thickness of the nonwoven fabric when pressed at 50 Pa,
A nonwoven fabric, the values obtained by the following (method of measuring the apparent thickness and thickness recovery rate of a nonwoven fabric after release from compression) satisfy the following requirement (2).
(2) The apparent thickness of the nonwoven fabric after compression and release is 2 mm or more and 8 mm or less.
(Method of measuring apparent thickness and thickness recovery rate of nonwoven fabric after releasing from compression)
(a) "Nonwoven fabric apparent thickness before compression": a load of 50 Pa is applied to a nonwoven fabric sample to measure its apparent thickness.
(b) Next, the nonwoven fabric of the measurement sample is compressed to 0.7 mm under a load of 20 kPa. This compressed state is maintained in an atmosphere at 50° C. for 24 hours, and then the compressed state is released and the sample is left in an atmosphere at 25° C. for 30 minutes.
(c) Then, a laser thickness gauge is used to measure the thickness under a load of 50 Pa. Measurements are taken at three locations, and the average value is taken as the measurement data to obtain the "apparent thickness of the nonwoven fabric after release from compression."
(d) Finally, the recovery rate of the nonwoven fabric apparent thickness is calculated using the following formula.
"Recovery rate of apparent thickness of nonwoven fabric after release from compression [%]"
= "apparent thickness of nonwoven fabric after compression and release" ÷ "apparent thickness of nonwoven fabric before compression" × 100
＜4＞
A nonwoven fabric containing thermoplastic fibers and having fusion points between the fibers,
The apparent thickness of the nonwoven fabric under a load of 50 Pa is 4 mm or more and 9 mm or less,
The apparent thickness of the nonwoven fabric when pressed at 2.5 kPa is half or less of the apparent thickness of the nonwoven fabric when pressed at 50 Pa,
A nonwoven fabric, the values obtained by the following (method of measuring the apparent thickness and thickness recovery rate of a nonwoven fabric after releasing from compression) satisfy both of the following requirements (1) and (2).
(1) The recovery rate of the apparent thickness of the nonwoven fabric after release from compression is 40% or more and 80% or less.
(2) The apparent thickness of the nonwoven fabric after compression and release is 2 mm or more and 8 mm or less.
(Method of measuring apparent thickness and thickness recovery rate of nonwoven fabric after releasing from compression)
(a) "Nonwoven fabric apparent thickness before compression": a load of 50 Pa is applied to a nonwoven fabric sample to measure its apparent thickness.
(b) Next, the nonwoven fabric of the measurement sample is compressed to 0.7 mm under a load of 20 kPa. This compressed state is maintained in an atmosphere at 50° C. for 24 hours, and then the compressed state is released and the sample is left in an atmosphere at 25° C. for 30 minutes.
(c) Then, a laser thickness gauge is used to measure the thickness under a load of 50 Pa. Measurements are taken at three locations, and the average value is taken as the measurement data to obtain the "apparent thickness of the nonwoven fabric after release from compression."
(d) Finally, the recovery rate of the nonwoven fabric apparent thickness is calculated using the following formula.
"Recovery rate of apparent thickness of nonwoven fabric after release from compression [%]"
= "apparent thickness of nonwoven fabric after compression and release" ÷ "apparent thickness of nonwoven fabric before compression" × 100

＜5＞
The nonwoven fabric according to any one of <1> to <4>, wherein the apparent thickness of the nonwoven fabric under a load of 50 Pa is 5 mm or more, preferably 6 mm or more, and more preferably 7 mm or more.
＜6＞
The nonwoven fabric according to any one of <1> to <5>, wherein the apparent thickness of the nonwoven fabric under a load of 50 Pa is 9 mm or less, and preferably 8.5 mm or less.
＜７＞
The nonwoven fabric according to any one of <1> to <6>, wherein the recovery rate of the apparent thickness of the nonwoven fabric after the compression and release is 45% or more, and preferably 50% or more.
＜8＞
The nonwoven fabric according to any one of <1> to <7>, wherein the recovery rate of the apparent thickness of the nonwoven fabric after the compression and release is 80% or less, preferably 70% or less, and more preferably 60% or less.

＜9＞
The nonwoven fabric according to any one of <1> to <8>, wherein the deformation stroke of the nonwoven fabric after the compression and release is 1 mm or more and 6 mm or less.
＜10＞
The nonwoven fabric according to any one of <1> to <9>, wherein the deformation stroke of the nonwoven fabric after compression and release is 1.5 mm or more, and preferably 2 mm or more.
<11>
The nonwoven fabric according to any one of <1> to <10> above, wherein the deformation stroke of the nonwoven fabric after compression and release is 5.5 mm or less, and preferably 5 mm or less.

＜12＞
The nonwoven fabric according to any one of <1> to <11> above, which is made of thermoplastic fibers.
＜13＞
The nonwoven fabric according to any one of <1> to <12>, which is made of core-sheath type conjugated fibers containing two or more different resin components, and in a core-sheath mass ratio of the conjugated fibers, the core ratio is larger than the sheath ratio.
＜14＞
The nonwoven fabric according to <13> above, wherein the endothermic peaks of the two or more different resin components are separated by 5° C. or more.
＜15＞
The nonwoven fabric according to any one of <1> to <14> above, wherein the elongation of the conjugated fiber is 100% or less, preferably 90% or less, and more preferably 85% or less.
＜16＞
The nonwoven fabric according to any one of <1> to <15> above, wherein the elongation of the conjugated fiber is 40% or more, preferably 50% or more, and more preferably 60% or more.

＜１７＞
The nonwoven fabric according to any one of <1> to <16>, wherein fusion points between fibers exist in the thickness center portion.
＜18＞
The nonwoven fabric according to <17>, wherein the number of fusion points per unit area in the thickness center portion is 100 pcs/mm2 or ^more and 300 pcs/mm2 or ^less .
＜19＞
The nonwoven fabric according to any one of <1> to <18> above, having an embossing rate of 15% or less and an uneven shape, preferably 10% or less, more preferably 5% or less, and more preferably 0% or more.

＜20＞
The nonwoven fabric according to any one of <1> to <19> above, wherein the degree of longitudinal orientation of the fibers is 55% or more, preferably 60% or more, and more preferably 65% or more.
＜21＞
The nonwoven fabric according to any one of <1> to <20> above, wherein the degree of longitudinal orientation of the fibers is 95% or less, preferably 90% or less, and more preferably 80% or less.

＜22＞
The nonwoven fabric according to any one of <1> to <21>, wherein the binder is present at fiber intersections in the thickness center portion.
＜23＞
The nonwoven fabric according to <22>, wherein the fiber intersections where the binder is present are fusion points between fibers.
＜24＞
The nonwoven fabric according to <23>, wherein the mass of the binder is 1% or more and 15% or less of the mass of the nonwoven fabric.

＜25＞
The nonwoven fabric according to any one of <1> to <24>, having an uneven shape including protrusions, recesses, and walls connecting the protrusions and the recesses in a thickness direction of the nonwoven fabric.
＜26＞
The nonwoven fabric according to <25>, wherein the uneven shape has one structure or a combination of two or more structures selected from the group consisting of solid protrusions, hollow protrusions, a single-layer fiber layer, a two-layer fiber layer, protrusions arranged in a scattered dot pattern in a planar direction, and protrusions and recesses arranged in a ridge-furrow pattern.
＜27＞
The nonwoven fabric according to any one of <1> to <26>, having an uneven shape on both sides.
＜28＞
A nonwoven fabric having one surface and an opposite surface opposite to the one surface,
The sheet has outer fiber layers on the one surface side and the opposite surface side, and a plurality of connecting portions disposed between the outer fiber layer on the one surface side and the outer fiber layer on the opposite surface side,
The nonwoven fabric according to any one of <1> to <27>, wherein the outer fibrous layer on one side and the outer fibrous layer on the opposite side and the connecting portion are partially fused to each other.
＜29＞
A nonwoven fabric having one surface and an opposite surface opposite to the one surface,
On the one surface side,
A plurality of vertical ridge portions protruding toward the one surface side in the thickness direction of the nonwoven fabric extend in one direction on the one surface side in a plan view, and are arranged side by side at a distance from each other in another direction on the one surface side in a plan view different from the one direction on the one surface side,
The nonwoven fabric according to any one of <1> to <28>, wherein the horizontal rib portions extending in the other direction on the one surface side are arranged so as to connect the vertical rib portions.
＜30＞
The nonwoven fabric according to <29>, wherein the vertical ridges and horizontal ridges on the one surface side have convex portions and concave portions between the convex portions and the concave portions are arranged in a ridge-groove pattern.
＜31＞
The nonwoven fabric according to any one of <1> to <30> above, which has a convex rib portion extending in one direction, the convex rib portion being formed by a plurality of convex portions connected in a ridge shape and having a shape in which narrow parts and wide parts are alternately connected in a planar view.

＜32＞
An absorbent article comprising the nonwoven fabric according to any one of <1> to <31>.
＜33＞
The absorbent article has a top sheet disposed on the skin contact side, a back sheet disposed on the non-skin contact side, and an absorbent body sandwiched between the top sheet and the back sheet,
An absorbent article having the nonwoven fabric according to any one of <1> to <31> as a topsheet.

The present invention will be explained in more detail below based on examples, but the present invention should not be construed as being limited thereto. In the examples, "parts" and "%" are all based on mass unless otherwise specified. In Table 1 below, "-" means that the item does not have a corresponding value, etc.

The "apparent thickness of nonwoven fabric under a load of 50 Pa" and the "apparent thickness of nonwoven fabric when compressed at 2.5 kPa" in Table 1 were measured in accordance with the above-mentioned (Method for measuring apparent thickness of nonwoven fabric under a load of 50 Pa). The "apparent thickness of nonwoven fabric after release from compression", "recovery rate of apparent thickness of nonwoven fabric after release from compression" and "deformation stroke of nonwoven fabric after release from compression" in Table 1 were measured based on the above-mentioned (Method for measuring apparent thickness and thickness recovery rate of nonwoven fabric after release from compression) and (Method for measuring deformation stroke of nonwoven fabric after release from compression).
The "core-sheath mass ratio" in Table 1 was measured based on the above-mentioned (method for measuring the mass ratio of the core component and the sheath component to the mass of a core-sheath type composite fiber), and the "elongation" was measured in accordance with JIS L1015 7.7.1.
Furthermore, "presence or absence of fusion points between fibers in the thickness center,""embossingrate,""degree of longitudinal orientation of fibers," and "presence or absence of binder at fiber intersections in the thickness center" in Table 1 were measured based on the above-mentioned (method for confirming the presence or absence of fusion points between fibers in the thickness center of a nonwoven fabric), (method for measuring the embossing rate), (method for measuring the longitudinal orientation of fibers), and (method for confirming the presence or absence of binder at fiber intersections in the thickness center of a nonwoven fabric).

Example 1
(1) Preparation of raw nonwoven fabric Raw nonwoven fabrics having the uneven shape shown in Figures 6 to 11 were prepared by the air-through method using core-sheath type thermoplastic composite fibers having the fiber diameters shown in Table 1. The size of the raw nonwoven fabric was 100 mm x 100 mm.
Specifically, the film was produced based on the manufacturing method described in paragraphs [0059] to [0065] of Patent Document 4. The first hot air blowing treatment was performed under conditions of a temperature of 160° C., a wind speed of 54 m/sec, and a blowing time of 6 seconds. The second hot air blowing treatment was performed under conditions of a temperature of 160° C., a wind speed of 6 m/sec, and a blowing time of 6 seconds.
(2) Preparation of binder coating solution A binder coating solution was prepared by mixing 10% by weight of a binder solution with a solid content of about 50% and 90% by weight of deionized water. A commercially available acrylic emulsion with high elasticity was used as the binder.
(3) Spraying of binder coating liquid Next, the binder coating liquid was evenly applied by spraying to the second surface (opposite surface) 1B of the raw nonwoven fabric, on which the convex streak portion 931 and the concave streak portion 936 were arranged. The amount of the binder coating liquid applied was 3.5 g/ ^m2 . This was measured by the change in the mass of the nonwoven fabric before and after the binder coating.
This produced nonwoven fabric sample A1 of Example 1 having the basis weight shown in Table 1. The binder was attached to the center of the nonwoven fabric in the thickness direction, and was present in a large amount at the fiber intersections in particular.
This nonwoven fabric sample A1 satisfies the above-mentioned requirements of (c. a layer of fibers that are core-sheath type composite fibers, in which the core ratio is greater than the sheath ratio in terms of the core-sheath mass ratio of the composite fibers), (e. a layer of low elongation fibers), (h. a layer having fibers with longitudinal orientation), and (i. a layer in which a binder is present at fiber intersections).

Example 2
Nonwoven fabric sample A2 of Example 2 was produced in the same manner as in Example 1, except that the basis weight was as shown in Table 1. The binder was adhered to the center of the nonwoven fabric in the thickness direction, and was present in a large amount at the fiber intersections in particular.
This nonwoven fabric sample A2 satisfies the above-mentioned requirements (c. a layer of fibers that are core-sheath type composite fibers, in which the core ratio is greater than the sheath ratio in terms of the core-sheath mass ratio of the composite fibers), (e. a layer of low elongation fibers), (h. a layer having fibers with longitudinal orientation), and (i. a layer in which a binder is present at fiber intersections).

Example 3
A nonwoven fabric sample A3 of Example 3 was produced in the same manner as in Example 1, except that the fiber diameter and basis weight were as shown in Table 1.
This nonwoven fabric sample A3 satisfies the above-mentioned requirements of (c. a layer of fibers that are core-sheath type composite fibers, in which the core ratio is greater than the sheath ratio in terms of the core-sheath mass ratio of the composite fibers), (e. a layer of low elongation fibers), (h. a layer having fibers with longitudinal orientation), and (i. a layer in which a binder is present at fiber intersections).

Example 4
Nonwoven fabric sample A4 of Example 4 was prepared in the same manner as in Example 1, except that in the preparation method described in paragraphs [0059] to [0065] of Patent Document 4, the height of the protrusions of the support was changed to 6.0 mm, thereby making the apparent thickness and basis weight of the nonwoven fabric under a load of 50 Pa as shown in Table 1, and the bulk was made lower than that of Example 1.
This nonwoven fabric sample A4 satisfies the above-mentioned requirements of (c. a layer of fibers that are core-sheath type composite fibers, in which the core ratio is greater than the sheath ratio in terms of the core-sheath mass ratio of the composite fibers), (e. a layer of low elongation fibers), (h. a layer having fibers with longitudinal orientation), and (i. a layer in which a binder is present at fiber intersections).

Example 5
Nonwoven fabric sample A5 of Example 5 was produced in the same manner as in Example 4, except that the core-sheath ratio and basis weight of the thermoplastic conjugate fiber were set as shown in Table 1. As shown in Table 1, the elongation of the thermoplastic conjugate fiber was lower than that of Example 1 due to the core-sheath ratio.
This nonwoven fabric sample A5 satisfies the above-mentioned requirements (c. a layer of fibers that are core-sheath type composite fibers, in which the core ratio is greater than the sheath ratio in terms of the core-sheath mass ratio of the composite fibers), (e. a layer of low elongation fibers), and (h. a layer having longitudinal fiber orientation).

Example 6
Nonwoven fabric sample A6 of Example 6 was produced in the same manner as in Example 4, except that the core-sheath ratio, elongation, basis weight, and fiber diameter of the thermoplastic conjugate fiber were as shown in Table 1, and elastic elastomer fiber was used instead of the thermoplastic conjugate fiber.
This nonwoven fabric sample A6 satisfies the above-mentioned requirements of (c. a layer of fibers that are core-sheath type composite fibers, in which the core ratio is greater than the sheath ratio in terms of the core-sheath mass ratio of the composite fibers), (d. a layer of elastomeric fibers), and (h. a layer having longitudinal fiber orientation).

(Example 7)
A nonwoven fabric sample A7 of Example 7 was produced in the same manner as in Example 4, except that the constituent components of the composite fibers were as shown in Table 1, the fiber intersections in the thickness center were not fused (no fused intersections), and the basis weight was as shown in Table 1.
Specifically, it was prepared by the method described in paragraphs [0059] to [0065] of Patent Document 4.
The fiber webs used to manufacture the nonwoven fabric were prepared by the following method. That is, two sheets of fiber web A with a basis weight of 10 g/ ^m2 were prepared using thermoplastic fibers of a core-sheath type (PET (core): PE (sheath) = 5: 5 (mass ratio)) with a fineness of 3.5 dtex. Next, one sheet of fiber web B with a basis weight of 10 g/ ^m2 was prepared using a single fiber (PET: 100%) with a fineness of 3.5 dtex. The fiber web B was sandwiched between the fiber webs A from above and below and used as the fiber web.
This nonwoven fabric sample A7 satisfies the above-mentioned requirements (e. layer of low elongation fiber) and (f. unfused fiber layer).

(Example 8)
Nonwoven fabric sample A8 of Example 8 was produced in the same manner as in Example 1, except that the raw nonwoven fabric was produced by the manufacturing method described in paragraphs [0049] to [0057] of JP 2019-44319 A and the support shown in Fig. 12 was used. Nonwoven fabric sample A8 had the uneven shape shown in Fig. 5.
In the above manufacturing method, the support male member 120 shown in FIG. 12 was a rectangular column with a height of 8 mm and a size of 2 mm x 2 mm when viewed from above. The pitch of the rectangular column was 5 mm in both the MD and CD directions. The support female member 130 shown in FIG. 12 was a metal member having a lattice-shaped protrusion 131 corresponding to the recess 122 of the support male member 120, and was pressed between the protrusions 121 of the support male member 120. The adjacent protrusions 121, 121 of the support female member 130 were arranged at a pitch of 5 mm, and the space into which the fibers were inserted when the support male member 120 and the support female member 130 were pressed was 0.5 mm on one side, and 1 mm on both sides of the protrusions 120 of the support male member 120. The hot air blowing treatment was performed under conditions of a temperature of 160° C., a wind speed of 6 m/sec, and a blowing time of 6 seconds.
This nonwoven fabric sample A8 satisfies the above-mentioned requirements of (c. a layer of fibers that are core-sheath type composite fibers, in which the core ratio is greater than the sheath ratio in terms of the core-sheath mass ratio of the composite fibers), (e. a layer of low elongation fibers), (h. a layer having fibers with longitudinal orientation), and (i. a layer in which a binder is present at fiber intersections).

(Comparative Example 1)
A nonwoven fabric with an uneven shape as described in Example 1 of Patent Document 3 was produced by the air-through method using core-sheath type thermoplastic conjugate fibers having the fiber diameters shown in Table 1. The basis weight was as shown in Table 1. The nonwoven fabric was used as nonwoven fabric sample C1 of Comparative Example 1 without being coated with a binder coating liquid.
This nonwoven fabric sample C1 satisfies the above-mentioned requirements (c. a layer of fibers that are sheath-core composite fibers, in which the core ratio is greater than the sheath ratio by mass of the composite fibers) and (e. a layer of low elongation fibers).

(Comparative Example 2)
A flat nonwoven fabric without irregularities was produced by the air-through method using core-sheath type thermoplastic composite fibers having the fiber diameters shown in Table 1. The basis weight was as shown in Table 1. The nonwoven fabric was used as nonwoven fabric sample C2 of Comparative Example 2 without being coated with a binder coating liquid.
This nonwoven fabric sample C2 satisfies the above-mentioned requirements (c. a layer of fibers that are sheath-core composite fibers, in which the core ratio is greater than the sheath ratio by mass of the composite fibers) and (e. a layer of low elongation fibers).

(Comparative Example 3)
A resin-bonded nonwoven fabric described in Example 1 of Patent Document 1 was produced using fibers (PET) having the fiber diameters shown in Table 1. The resin-bonded nonwoven fabric was produced by spray coating using the resin-bonded coating solution used in Example 1. The coating amount was 16.6 g/ ^m2 . This resin-bonded nonwoven fabric was designated nonwoven fabric sample C3 of Comparative Example 3.
The nonwoven fabric sample C3 had no irregularities and was flat.
Furthermore, this nonwoven fabric sample C3 satisfies the above-mentioned requirements of (e. layer of low elongation fibers), (f. unfused fiber layer), and (i. layer having binder at fiber intersections).

(Comparative Example 4)
The nonwoven fabric located on the back of the surface material was removed from a medium-sized tape diaper of Pampers Ultra Thin Dry Fresh (obtained in May 2018) manufactured by The Procter & Gamble Company sold in China, and the nonwoven fabric sample was placed in a beaker containing 100 mL of ethyl acetate and stirred for 30 minutes, after which the nonwoven fabric sample was removed and dried. The nonwoven fabric thus obtained was designated as nonwoven fabric sample C4 of Comparative Example 4.
The nonwoven fabric sample C4 had no irregularities and was flat.
Furthermore, this nonwoven fabric sample C4 satisfies the above-mentioned requirements of (e. layer of low elongation fibers), (f. unfused fiber layer), and (i. layer having binder at fiber intersections).

(Comparative Example 5)
Based on Example 1 described in JP 2012-136803 A, a nonwoven fabric sample C5 of Comparative Example 5 was produced.
This nonwoven fabric sample C5 satisfies the above-mentioned requirements (c. a layer of fibers that are sheath-core composite fibers and in which the core ratio is greater than the sheath ratio by mass of the composite fibers) and (e. a layer of low elongation fibers).

The following measurements and tests were carried out for the above-mentioned Examples and Comparative Examples.
(1) Measurements of items 6 to 11 and 13 to 15 in Table 1 below Each nonwoven fabric sample was measured based on the respective measurement methods corresponding to each item.
(2) Measurement of item 12 in Table 1 below The above-mentioned (Method for confirming the presence or absence of binder at fiber intersections in the thickness center of a nonwoven fabric) was applied mutatis mutandis to measure the presence or absence of dyed fiber intersections in the observation images of each of the front and back surfaces (first surface side and second surface side) of the nonwoven fabric.
(3) Test of item 16 in Table 1 below (feel: MMD (average coefficient of friction variation) test)
The variation in the average coefficient of friction of the nonwoven fabric surface, MMD, was measured using an automatic surface tester (KESFB4-A-SE: manufactured by Kato Tech Co., Ltd.). A test piece measuring 20 cm x 20 cm was prepared and attached to a test table with a smooth metal surface. The contact surface of the contactor was pressed against the test piece with a force of 49 cN, and the test piece was moved horizontally 2 cm at a constant speed of 0.1 cm/sec. A uniaxial tension of 19.6 cN/cm was applied to the test piece. The contactor was made by arranging 20 piano wires with a diameter of 0.5 mm and bending them into a U-shape with a width of 10 mm, and the contact surface was pressed against the test piece with a force of 49 cN by a weight. The measured value of the average deviation of the coefficient of friction is expressed as the MMD value. This measurement was performed in both MD and CD, and the average value was calculated using the following formula (S2), which was used as the average deviation of the coefficient of friction.
Average deviation of friction coefficient = {(MMD _MD ² + MMD _CD ² )/2} ^1/2 (S2)
The average deviation of the friction coefficient indicates the degree of variation in friction, with a smaller value indicating a smoother feel when touched by hand.

As shown in Table 1, the nonwoven fabric samples A1 to A8 of Examples 1 to 8 had an apparent thickness of 4 mm or more under a load of 50 Pa, which was thicker than the nonwoven fabric samples C2 to C5 of Comparative Examples 2 to 5, and either or both of the apparent thickness and recovery rate of the nonwoven fabric after compression and release were greater than those of the nonwoven fabric samples C1 to C5 of Comparative Examples 1 to 5, showing excellent thickness recovery. In addition, the compressibility from the apparent thickness under a load of 50 Pa to the apparent thickness when pressurized at 2.5 kPa was also sufficiently high. As a result, the nonwoven fabric samples A1 to A8 of Examples 1 to 8 could be felt to have a sufficient thickness under a light load (load of 50 Pa) such that the skin touched the nonwoven fabric surface, and when a heavy load (load of 2.5 kPa) was applied to strongly press the nonwoven fabric, the thickness was sufficiently crushed, and soft deformability and cushioning could be felt. This changing tactile sensation was maintained even after compression and release. In other words, it was found that the nonwoven fabric of the present invention has high cushioning properties and a fluffy texture can be felt both before and after compression and release.
Furthermore, the nonwoven fabric samples A1 to A8 of Examples 1 to 3 had a sufficiently smaller MMD and better texture than the binder-containing nonwoven fabrics C3 to C5 of Comparative Examples 3 to 5. This is because the nonwoven fabric samples A1 to A8 of Examples 1 to 3 had a larger apparent thickness under a load of 50 Pa and a larger apparent thickness after compression and release than the nonwoven fabrics C3 to C5 of Comparative Examples 3 to 5. In addition, the nonwoven fabric samples A1 to A8 of Examples 1 to 3 were able to suppress the effects of the unevenness and adhesiveness of the binder itself by using the thickness characteristics described above, thereby realizing a high level of smoothness when touched by hand.
In addition, in the measurement of MMD (variation of mean coefficient of friction), which indicates texture, the terminal that measures friction is subjected to the irregular adhesive force from the binder on the fiber surface, which causes the average coefficient of friction to fluctuate greatly. In addition, when the fibers are strongly bonded to each other by the binder and hardened, when the terminal picks up the frictional force of the nonwoven fabric surface, it cannot flexibly deform, and the frictional force to the terminal fluctuates. These microscopic phenomena, such as hardening and stickiness of the fibers, cause a large difference in texture. The difference in MMD values shown in Table 1, even if small numerically, means a significant difference in texture as a feeling on the delicate skin surface.

Any numerical limit or range set forth herein includes the recited end values of that numerical limit or range, and all values and subranges within that numerical limit or range are expressly included as if expressly stated.
As used herein, the words "a,""an," and "the like" mean "one or more."
Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings, and it is therefore to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.
All patents and other references cited above are incorporated herein by reference in their entirety as if fully set forth herein as if fully set forth.

6 Fiber intersection 61 Dyed fiber intersection 7 Fiber 71 Black dots 80, 90 Nonwoven fabrics 100S, 100W with uneven shapes Nonwoven fabric 105 Thickness center of nonwoven fabric C Reference circle L, L1, L2, L3, L4 Reference line

Claims (7)

A nonwoven fabric containing thermoplastic fibers and having fusion points between the fibers,
The thermoplastic fiber is a core-sheath type composite fiber containing two or more different resin components, and the core ratio of the composite fiber is greater than the sheath ratio.
A binder is present at the fusion points between the fibers in the thickness center portion,
The apparent thickness of the nonwoven fabric under a load of 50 Pa is 4 mm or more,
The apparent thickness of the nonwoven fabric when pressed at 2.5 kPa is half or less of the apparent thickness of the nonwoven fabric when pressed at 50 Pa,
A nonwoven fabric, the values obtained by the following (method of measuring the apparent thickness and thickness recovery rate of a nonwoven fabric after releasing from compression) satisfy either or both of the following requirements (1) and (2).
(1) The recovery rate of the apparent thickness of the nonwoven fabric after release from compression is 40% or more.
(2) The apparent thickness of the nonwoven fabric after compression and release is 2 mm or more and 8 mm or less.
(Method of measuring apparent thickness and thickness recovery rate of nonwoven fabric after releasing from compression)
(a) "Nonwoven fabric apparent thickness before compression": a load of 50 Pa is applied to a nonwoven fabric sample to measure its apparent thickness.
(b) Next, the nonwoven fabric of the measurement sample is compressed to 0.7 mm under a load of 20 kPa. This compressed state is maintained in an atmosphere at 50° C. for 24 hours, and then the compressed state is released and the sample is left in an atmosphere at 25° C. for 30 minutes.
(c) Then, a laser thickness gauge is used to measure the thickness under a load of 50 Pa. Measurements are taken at three locations, and the average value is taken as the measurement data to obtain the "apparent thickness of the nonwoven fabric after release from compression."
(d) Finally, the recovery rate of the nonwoven fabric apparent thickness is calculated using the following formula.
"Recovery rate of apparent thickness of nonwoven fabric after release from compression [%]"
= "apparent thickness of nonwoven fabric after compression and release" ÷ "apparent thickness of nonwoven fabric before compression" × 100 The nonwoven fabric according to claim 1, wherein the deformation stroke of the nonwoven fabric after the compression and release is 1 mm or more and 6 mm or less. The nonwoven fabric according to claim 1 or 2, which is made of thermoplastic fibers. The nonwoven fabric according to any one of claims 1 to 3 , wherein the conjugated fibers have an elongation of 100% or less. The nonwoven fabric according to any one of claims 1 to 4 , wherein the degree of longitudinal orientation of the fibers is 55% or more. The nonwoven fabric according to any one of claims 1 to 5 , wherein the mass of the binder is 1% or more and 15% or less of the mass of the nonwoven fabric. An absorbent article comprising the nonwoven fabric according to any one of claims 1 to 6 .

Images