JP7486642B2 - Surface material for absorbent articles - Google Patents

Description

The present invention relates to a surface material for absorbent articles such as disposable diapers.

When absorbent articles such as disposable diapers, sanitary napkins, panty liners (discharge sheets), and incontinence pads are worn, skin rashes may occur due to sweating, etc. Therefore, in order to prevent the occurrence of rashes, absorbent articles using antibacterial agents have been proposed.
For example, Patent Documents 1 and 2 describe absorbent articles in which an antibacterial agent is kneaded into the fibers constituting the surface material that comes into contact with the wearer's skin.

JP 2006-55187 A JP 2021-52938 A

In absorbent articles that use antibacterial agents, the antibacterial agent is poorly soluble in water, and this means that urine and other excretory fluids penetrate the surface sheet (surface material) before the antibacterial effect can be fully exerted, making it difficult for the antibacterial effect to be efficiently exerted, which has been an issue.

The present invention relates to a surface material for absorbent articles that can exhibit an efficient antibacterial effect.

The surface material of the absorbent article according to one embodiment of the present invention has a skin side and a non-skin side.
The skin side surface has a plurality of protrusions and a plurality of recesses located between the plurality of protrusions.
The surface material constitutes an upper layer that constitutes the skin side and the non-skin side.
The convex portion has a hollow portion therein, and the hollow portion is located between the upper layer and the lower layer.
The fibers constituting the non-skin side of the upper layer that forms the hollow portion and the fibers constituting the skin side of the upper layer include metal oxide antibacterial agent-containing fibers that contain a metal oxide antibacterial agent.

An absorbent article according to one aspect of the present invention includes an absorbent body and a surface material located on a skin side of the absorbent body.
The facing has a skin side and a non-skin side.
The skin side of the surface material has a plurality of protrusions and a plurality of recesses located between the plurality of protrusions.
The surface material constitutes an upper layer that constitutes the skin side and the non-skin side.
The convex portion has a hollow portion therein, and the hollow portion is located between the upper layer and the lower layer.
The fibers constituting the non-skin side of the upper layer that forms the hollow portion and the fibers constituting the skin side of the upper layer include metal oxide antibacterial agent-containing fibers that contain a metal oxide antibacterial agent.

The surface material of the absorbent article of the present invention allows for efficient antibacterial effects.

FIG. 1 is a diagram showing an example of a disposable diaper as one embodiment of an absorbent article of the present invention, and is a schematic plan view of the skin side (surface material side) showing the state in which the elastic members of each part are stretched and spread out flat. 2 is a schematic cross-sectional view of the absorbent article taken along line II-II in FIG. 1. 3 is a schematic cross-sectional view showing an enlarged view of a portion of a surface material that constitutes a part of the disposable diaper. FIG. FIG. 2 is a schematic perspective view of a metal oxide antibacterial agent-containing fiber used in the surface material of the embodiment.

Below, an absorbent article equipped with the surface material of the present invention will be described with reference to the drawings, taking a disposable diaper as an example.

<Overall composition of disposable diapers>
The disposable diaper 1 of this embodiment shown in Fig. 1 is a so-called flat-type disposable diaper. However, the surface material of the present invention is not limited to flat-type disposable diapers, and can also be applied to pants-type disposable diapers.
The disposable diaper 1 and each of the components constituting the disposable diaper 1 have a vertical direction X corresponding to the front-to-back direction of a wearer, and a horizontal direction Y corresponding to the left-to-right direction of the wearer and perpendicular to the vertical direction X. Furthermore, the disposable diaper 1 and each of the components constituting the disposable diaper 1 have a thickness direction Z perpendicular to both the vertical direction X and the horizontal direction Y.
In this specification, the "skin side" of each component refers to the side that is closest to the wearer's skin when the disposable diaper is worn. The "non-skin side" of each component refers to the side that is opposite to the skin side of the wearer when the disposable diaper is worn. In addition, with respect to the thickness direction Z, the side that is closest to the wearer's skin when worn may be referred to as the "upper" and the side that is closest to the clothing may be referred to as the "lower."
The disposable diaper 1 will be referred to as diaper 1 hereinafter.
In addition, in this embodiment, a tape-type disposable diaper is taken as an example, but the present invention can also be applied to pants-type, sanitary napkins, panty liners, and incontinence pads.

As shown in FIG. 1 , the diaper 1 is divided into a ventral region A located on the ventral side in the longitudinal direction X, a dorsal region B located on the dorsal side in the longitudinal direction X, and a crotch region C located between the ventral region A and the dorsal region B.
The back region B includes side portions protruding outward in the lateral direction Y from the crotch region C. Fastening tapes 9 are provided on the side edges of the side portions in the lateral direction Y. Similarly, the abdominal region A includes side portions protruding outward in the lateral direction Y from the crotch region C.
A landing tape (not shown) for adhering the fastening tape 9 is provided on the non-skin side of the abdominal region A. The landing tape is made of a female member of a mechanical hook-and-loop fastener. The fastening tape 9 has a fastening portion 91 made of a male member of a mechanical hook-and-loop fastener.
The crotch region C is narrower than the ventral region A and the dorsal region B, with leg openings narrowed inward in the lateral direction Y, and is positioned around the wearer's crotch area, including the urination area and anus, when worn.
It should be noted that "when worn" here refers to a state in which the normally expected appropriate wearing position is maintained.

As shown in Figures 1 and 2, the diaper 1 comprises a surface material (top sheet) 2, a back material (back sheet) 3, an absorbent 4, side sheets 5, a pair of fastening tapes 9, an intermediate sheet 7, and a leak-proof sheet 8. The diaper 1 has a configuration in which the back material 3, the leak-proof sheet 8, the absorbent 4, the intermediate sheet 7, and the surface material 2 are laminated in the thickness direction Z. These components are joined together by known joining means such as a hot melt adhesive.

The absorbent body 4 extends along the longitudinal direction X, and is disposed between the front material 2 and the back material 3. That is, the absorbent body 4 is disposed on the non-skin side of the front material 2. The absorbent body 4 absorbs liquid excrement (hereinafter sometimes simply referred to as "liquid" or "excrement") such as moisture contained in the wearer's urine or feces from the surface on the front material 2 side, and retains the liquid by diffusing it internally.
The absorbent body 4 has an absorbent core 40 and a core wrap sheet 41 .
The absorbent core 40 is mainly composed of an absorbent material capable of retaining liquid. Specifically, the absorbent core 40 has a structure in which a hydrophilic fiber stack is supported with an absorbent polymer, or a structure made of only a water-absorbent polymer, or the like.
The core wrap sheet 41 covers the absorbent core 40 and has a function of, for example, maintaining the shape of the absorbent core 40. The core wrap sheet 41 is formed of, for example, a thin, soft paper such as tissue paper or a liquid-permeable nonwoven fabric.

The surface material 2 is disposed so as to contact the wearer's skin when the diaper 1 is worn. The surface material 2 is disposed on the skin side 4a side (upper side in the thickness direction Z) of the absorbent body 4, and constitutes, for example, the center in the lateral direction Y of the skin side of the diaper 1. The surface material 2 is configured as a liquid-permeable sheet material, and is formed of a nonwoven fabric made of synthetic or natural fibers, or the like.
The surface material 2 has a skin side 2a and a non-skin side 2b.
The surface material 2 will be described in detail later.

An intermediate sheet 7 may be provided between the surface material 2 and the absorbent body 4. The intermediate sheet 7 may be a nonwoven fabric obtained by various manufacturing methods. The intermediate sheet 7 is arranged from the viewpoint of improving the permeability of liquid from the surface material 2 to the absorbent body 4 and preventing the liquid absorbed by the absorbent body 4 from returning to the surface material 2.

The backing material 3 is disposed on the non-skin side (lower in the thickness direction Z) of the absorbent body 4, and constitutes, for example, almost the entire non-skin side of the diaper 1, forming the exterior of the diaper 1 when worn. The backing material 3 is preferably leak-proof, and is formed, for example, from a sheet material that has properties such as low liquid permeability, water vapor permeability, and water repellency.

The pair of side sheets 5 are disposed on the lateral sides in the lateral direction Y of the surface material 2, and for example, constitute the lateral sides in the lateral direction Y of the skin side of the diaper 1. The side sheets 5 are desirably leak-proof, and are formed of a sheet material having functions such as low liquid permeability, water vapor permeability, and water repellency. The pair of side sheets 5 are disposed such that the central sides in the lateral direction Y overlap the surface material 2, and the lateral sides in the lateral direction Y extend to the outside of the surface material 2 and are joined to the back surface material 3.
In the diaper 1, the side sheets 5 are provided with thread-like or strip-like elastic members 50, thereby forming standing gather forming sheets.

The leak-proof sheet 8 is made of a liquid-impermeable or liquid-difficult-to-permeate resin film and covers the skin side of the backing material 3.

<Surface material>
The surface material 2 will now be described.

[Schematic configuration of surface material]
The surface material 2 of this embodiment is an uneven surface material having an uneven surface. More specifically, as shown in Fig. 3, the skin side surface 2a is an uneven surface having a plurality of hollow protrusions 33 and a plurality of recesses 34, and the non-skin side surface 2b is a flat surface.
Since the skin side 2a is an uneven surface, when worn, the skin side 2a of the surface material 2 partially comes into contact with the skin. That is, when worn, the surface material 2 is easily brought into contact with the skin partially, more specifically, the tops of the convex portions 33 and the areas nearby. This reduces the stickiness and stuffiness caused by the skin side 2a of the surface material 2 coming into contact with the skin over its entire surface, as well as the irritation caused by rubbing, and suppresses skin troubles such as inflammation, eczema, and skin rash.
In this specification, "flat" means that the surface is flat without any irregularities macroscopically, and the presence of relatively small irregularities that may occur due to the fiber structure is permitted. For example, irregularities in which the difference between the top of the protrusion and the bottom of the recess in the thickness direction is less than 0.3 mm are permitted.

As shown in FIG. 3, the surface material 2 is constructed by laminating a lower layer LL and an upper layer UL formed on the lower layer LL. The lower layer LL constitutes the non-skin side 2b of the surface material 2. The upper layer UL constitutes the skin side 2a of the surface material 2.

As shown in FIG. 3, the surface material 2 has a plurality of recesses 34 and a plurality of protrusions 33 on its skin side 2a. A plurality of protrusions 33 are formed on one surface of the skin side 2a. The protrusions 33 are configured to protrude toward the skin side, and between the protrusions 33, recesses 34 are formed that are recessed toward the non-skin side.

The convex portion 33 has a flat lower layer LL portion and an upper layer UL portion that protrudes in a dome shape toward the wearer's skin when the diaper 1 is assembled.
The inside of the protruding portion 33 is hollow, and the protruding portion 33 has a hollow portion 10. The hollow portion 10 is located between the upper layer UL and the lower layer LL, and is a space surrounded by the non-skin side surface ULb of the upper layer UL and the skin side surface LLa of the lower layer LL.
The plurality of protrusions 33 are formed, for example, in a staggered pattern. The plurality of recesses 34 are also formed in a staggered pattern. The shapes and arrangements of the protrusions 33 and recesses 34 are not particularly limited.

The surface material 2 has a compressed region 52a in which the upper layer UL and the lower layer LL are partially compressed and joined together to compress the fibers, and a convex region 52b in which the upper layer UL and the lower layer LL are not compressed and the upper layer UL protrudes toward the skin to form a convex portion 33.
The recess 34 is formed by the compressed region 52a and the side surface of the protrusion 33 located around the compressed region 52a. The recess 34 has a space 30 that easily stores excrement.
The consolidation in the consolidation region 52a may be performed by a method involving melting of the fiber material constituting the surface material 2, or may be performed by a method not involving melting of the fiber material. Specific examples of the compression process involving melting of the fiber material include known embossing processes such as embossing with heat and ultrasonic embossing, and the consolidation region 52a is also referred to as an embossed portion.

As shown in FIG. 3, in the surface material 2, the upper layer UL is formed by laminating a first layer 21 and a second layer 22 positioned in that order from the skin side to the non-skin side (from top to bottom in the figure).
The skin side surface of the first layer 21 constitutes the skin side surface ULa of the upper layer UL. The skin side surface ULa constitutes the skin side surface 2a of the facing. The skin side surface ULa is a surface that can come into direct contact with the wearer's skin.
The non-skin side of the second layer 22 constitutes the non-skin side ULb of the upper layer UL.

As shown in FIG. 3, in the surface material 2, the lower layer LL includes a third layer 23 that constitutes the skin side LLa of the lower layer LL. In the surface material 2 of this embodiment, the lower layer LL has a one-layer structure, is composed of the third layer 23, and the skin side LLa of the lower layer LL can be said to be the skin side 23a of the third layer 23. In the following description, the lower layer LL will be referred to as the third layer 23, and the skin side LLa of the lower layer LL will be referred to as the skin side 23a of the third layer 23.

The first layer 21, the second layer 22, and the third layer 23 are each made of a sheet-like material of a fibrous material. As the sheet-like material, various nonwoven fabrics can be used, such as nonwoven fabrics manufactured by the carding method, spunbond nonwoven fabrics, meltblown nonwoven fabrics, spunlace nonwoven fabrics and needlepunch nonwoven fabrics, and meltblown nonwoven fabrics, spunlace nonwoven fabrics and needlepunch nonwoven fabrics.

[Configuration of the first layer]
As shown in Fig. 3, the first layer 21 is made of a fiber assembly, and the fibers constituting the first layer 21 are referred to as first fibers 61. The first fibers 61 are fibers containing a metal oxide antibacterial agent. In this embodiment, a case where all the first fibers 61 constituting the first layer 21 are fibers containing a metal oxide antibacterial agent will be described as an example. Hereinafter, the first fibers 61 will be described as first fibers containing a metal oxide antibacterial agent 61. The metal oxide antibacterial agent kneaded into the fibers containing a metal oxide antibacterial agent is shown as reference numeral 6 in Fig. 4 described later, and hereinafter will be referred to as the metal oxide antibacterial agent 6.
The first layer 21 may be configured to include both fibers containing a metal oxide antibacterial agent and fibers not containing a metal oxide antibacterial agent.

The first metal oxide antibacterial agent-containing fiber 61 is formed by kneading a metal oxide antibacterial agent 6 into the fiber. In the first metal oxide antibacterial agent-containing fiber 61, the metal oxide antibacterial agent is more effectively prevented from falling off the fiber compared to when an antibacterial agent is attached to the fiber by spraying, coating, etc. By kneading the metal oxide antibacterial agent 6 into the fiber, the metal oxide antibacterial agent 6 is less likely to migrate to other layers together with excreted liquid, and is more likely to remain in the surface material 2. The same is true for the second metal oxide antibacterial agent-containing fiber 621 described below.
The fibers containing a metal oxide antibacterial agent and the fibers not containing a metal oxide antibacterial agent will be described in detail later.

[Configuration of the second layer]
The second layer 22 is made of a fiber assembly, and the fibers constituting the second layer 22 are referred to as second fibers 62. The second fibers 62 include metal oxide antibacterial agent-containing fibers 621 (hereinafter referred to as second metal oxide antibacterial agent-containing fibers 621) which are fibers containing a metal oxide antibacterial agent 6, and metal oxide antibacterial agent-free fibers 622 (hereinafter referred to as second metal oxide antibacterial agent-free fibers 622). The second metal oxide antibacterial agent-containing fibers 621 are formed by kneading the metal oxide antibacterial agent 6 into the fibers.

[Configuration of the third layer]
The third layer 23 is made of a fiber assembly, and the fibers constituting the third layer 23 are referred to as third fibers 63. In this embodiment, an example will be described in which all of the third fibers 63 constituting the third layer 23 are fibers not containing a metal oxide antibacterial agent. Hereinafter, the third fibers 63 will be referred to as third fibers not containing a metal oxide antibacterial agent. The third layer 23 may be composed of both fibers not containing a metal oxide antibacterial agent and fibers containing a metal oxide antibacterial agent.

[Overall composition of surface material]
In Fig. 3, the first metal oxide antibacterial agent-containing fibers 61 constituting the first layer 21 are shown as solid lines. The second fibers 62 (including the second metal oxide antibacterial agent-containing fibers 621 and the second metal oxide antibacterial agent-free fibers 622) constituting the second layer 22 are shown as lines with diagonal lines. The third metal oxide antibacterial agent-free fibers 63 constituting the third layer 23 are shown as lines with only a white outline. In Fig. 4, the small circles with only a white outline and the small circles with black interiors are both schematic representations of fusion between fibers.

In the surface material 2 of this embodiment, the skin side ULa and non-skin side ULb of the upper layer UL are composed of fibers containing a metal oxide antibacterial agent made of metal oxide. On the other hand, the skin side LLa of the lower layer LL is composed of fibers not containing a metal oxide antibacterial agent, which does not have a metal oxide antibacterial agent kneaded into them.

[Antibacterial Agent]
As the metal oxide antibacterial agent, zinc oxide, silver oxide, aluminum oxide, calcium oxide, magnesium oxide, copper oxide, etc. can be used. These metal oxide antibacterial agents may be used alone or in combination of two or more. Among these, it is preferable to use zinc oxide in terms of antibacterial properties, safety, and cost.

The metal oxide antibacterial agent is preferably poorly soluble or insoluble in water, so that the metal oxide antibacterial agent is less likely to migrate to other layers.
In this embodiment, an example will be given in which poorly water-soluble zinc oxide is used as the metal oxide antibacterial agent.
There are various theories about the antibacterial mechanism of zinc oxide. For example, one theory is that zinc ions destabilize the cell membrane of bacteria, inducing cell death, and another is that zinc oxide reacts with water, generating hydrogen peroxide that suppresses the action of bacteria.

Zinc oxide is poorly soluble in water and therefore does not easily migrate to other layers such as the absorbent body 4 along with the excreted liquid that moves through the surface material 2 in the thickness direction Z, and is therefore likely to remain in the surface material 2. In addition, zinc oxide is kneaded into the fibers, so that it is more likely to remain in the surface material 2.
In this embodiment, the skin side ULa and non-skin side ULb of the upper layer UL are composed of fibers containing a metal oxide antibacterial agent, and in the surface material 2, the metal oxide antibacterial agent is in a form that tends to remain on the skin side ULa and non-skin side ULb of the upper layer UL.

[Metal oxide antibacterial agent blended fiber]
The first metal oxide antibacterial agent-containing fiber 61 and the second metal oxide antibacterial agent-containing fiber 621 can be obtained, for example, through a process of spinning a synthetic resin into which a metal oxide antibacterial agent has been previously mixed.

The first metal oxide antibacterial agent blended fiber 61 and the second metal oxide antibacterial agent blended fiber 621 may be, for example, a single fiber made of one type of synthetic resin (thermoplastic resin) or a blend polymer made by mixing two or more types of synthetic resins, or may be a composite fiber. The composite fiber referred to here is a synthetic fiber (thermoplastic fiber) obtained by combining two or more types of synthetic resins with different components in a spinneret and spinning them simultaneously, and the multiple components are each continuous in the length direction of the fiber and bonded to each other within the single fiber. The form of the composite fiber can be a core-sheath type, a side-by-side type, etc.

From the viewpoint of efficient expression of the antibacterial effect, it is preferable that the metal oxide antibacterial agent is exposed on the surface of the fiber blended with the metal oxide antibacterial agent.
From the viewpoint of efficiently exposing the metal oxide antibacterial agent to the fiber surface, it is particularly preferable that the first metal oxide antibacterial agent-containing fiber 61 and the second metal oxide antibacterial agent-containing fiber 621 are core-sheath type fibers.
As shown in Figure 4, a first metal oxide antibacterial agent-blended fiber 61 (second metal oxide antibacterial agent-blended fiber 621) having a metal oxide antibacterial agent 6 kneaded therein has a core portion 61C (621C) and a sheath portion 61S (621S). The metal oxide antibacterial agent 6 is blended only in the sheath portion 61S (621S). By blending the metal oxide antibacterial agent 6 only in the sheath portion 61S (621S) in this way, it is possible to easily expose the metal oxide antibacterial agent 6 on the fiber surface with a small content of the metal oxide antibacterial agent.

In order to efficiently and effectively prevent skin troubles using the metal oxide antibacterial agent 6 and to maintain a good balance of normal bacteria on the skin, the proportion of the metal oxide antibacterial agent 6 in the core-sheath type metal oxide antibacterial agent-containing fiber (first metal oxide antibacterial agent-containing fiber 61 or second metal oxide antibacterial agent-containing fiber 621) is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, preferably 2.5% by mass or less, more preferably 2.0% by mass or less, preferably 0.05% by mass or more and 2.5% by mass or less, and more preferably 0.1% by mass or more and 2.0% by mass or less.
The method for calculating the proportion of the metal oxide antibacterial agent in the fiber containing the metal oxide antibacterial agent will be described later.
In addition, in the core-sheath type metal oxide antibacterial agent-containing fiber (first metal oxide antibacterial agent-containing fiber 61 or second metal oxide antibacterial agent-containing fiber 621), the metal oxide antibacterial agent 6 is exposed on the fiber surface, and the skin trouble prevention effect of the metal oxide antibacterial agent 6 is efficiently and effectively exerted, and from the viewpoint of maintaining a good balance of normal bacteria on the skin, it is preferable that the metal oxide antibacterial agent is contained only in the sheath portion. In the core-sheath type metal oxide antibacterial agent-containing fiber (first metal oxide antibacterial agent-containing fiber 61 or second metal oxide antibacterial agent-containing fiber 621), from the above viewpoint, the ratio of the metal oxide antibacterial agent 6 to the resin constituting the sheath portion (61S or 621S) is preferably 0.1 mass% or more and 5.0 mass% or less, more preferably 0.2 mass% or more and 4.0 mass% or less.

The core-sheath type first metal oxide antibacterial agent-blended fiber 61 (second metal oxide antibacterial agent-blended fiber 621) that serves as the raw fiber may have a core 61C (62C) made of PET (polyethylene terephthalate) or PP (polypropylene), and a sheath 61S (62S) made of PE (polyethylene) kneaded with a metal oxide antibacterial agent (zinc oxide), and may have a core-sheath ratio of 20/80 to 80/20 by mass. The core-sheath ratio refers to the mass ratio (core/sheath) of the resins that make up the core and sheath.

The particle size of the metal oxide antibacterial agent 6 made of metal oxide is appropriately set in consideration of the thickness of the fibers (first metal oxide antibacterial agent-containing fiber 61 and second metal oxide antibacterial agent-containing fiber 621) to which the metal oxide antibacterial agent is blended and the ease of kneading the metal oxide antibacterial agent into the fibers. In general, the average particle size of the metal oxide antibacterial agent is 1.0 μm or more and 7 μm or less, expressed as the volume cumulative particle size _D50 at a cumulative volume of 50% by volume according to a laser diffraction scattering particle size distribution measurement method.

[Fibers without antibacterial agents]
The second metal oxide antibacterial agent-free fiber 622 and the third metal oxide antibacterial agent-free fiber 63 may be, for example, a single fiber made of one type of synthetic resin (thermoplastic resin) or a blend polymer made by mixing two or more types of synthetic resins, or may be a composite fiber.
The second metal oxide antibacterial agent-free fiber 622 and the third metal oxide antibacterial agent-free fiber 63 are, for example, core-sheath type composite fibers having a core made of PET (polyethylene terephthalate) or PP (polypropylene) and a sheath made of PE (polyethylene), with a core-sheath ratio of 20/80 to 80/20 by mass.

[Hollow and recessed parts]
As described above, the protrusion 33 has therein the hollow portion 10. In the hollow portion 10, the excreted liquid that is supplied to the surface material 2 and passes through the upper layer UL tends to temporarily remain.
Moreover, in the recesses 34, excrement tends to remain due to their concave shape. In addition, in the surface material 2 of this embodiment, the consolidated regions 52a constituting part of the recesses 34 and their vicinity have a higher fiber density and a smaller inter-fiber distance due to fusion or compression between the fibers than the surrounding areas (areas roughly corresponding to the convex regions 52b that are not compressed). Therefore, the consolidated regions 52a and their vicinity are configured to easily draw excrement liquid but are difficult for liquid to permeate due to the difference in fiber density with the surrounding areas, making it easier for excrement to remain in the recesses 34.
In this way, the hollow portion 10 and the recess 34 are designed to facilitate retention of excrement from the wearer.

In the recess 34, the skin side surface ULa of the upper layer UL is the surface that comes into direct contact with excrement remaining in the recess 34.
In the hollow portion 10, the non-skin side surface ULb of the upper layer UL is the surface that comes into direct contact with excrement accumulated in the hollow portion 10.

Here, because diapers are designed to prevent leakage, the inside of the diaper is in a hot and humid environment due to moisture from sweat, urine, etc. As such, the inside of the diaper is an environment in which the skin becomes steamy and macerated, which weakens the skin's barrier function, and also in which bacteria easily grow inside the diaper after urination or defecation.
Feces also contain enzymes such as proteolytic enzymes and lipolytic enzymes, as well as intestinal bacteria such as Escherichia coli and Staphylococcus aureus. Staphylococcus aureus is a bad bacterium that has a negative effect on the skin. When urination occurs, the urea contained in the urine is broken down by Staphylococcus aureus and converted into ammonia, creating an alkaline environment inside the diaper. When the diaper becomes an alkaline environment, the activity of Staphylococcus aureus becomes active, and Staphylococcus aureus produces toxins that cause skin problems such as inflammation, eczema, and skin rashes. In addition, if there is feces in the diaper, the alkaline environment inside the diaper activates the enzymes in the feces, irritating the skin, which has been macerated and has a weakened barrier function, and is prone to causing skin problems.

In contrast, in the diaper 1 using the surface material 2 of this embodiment, the skin side 2a (skin side ULa of the upper layer UL) of the surface material 2 that comes into contact with the wearer's skin contains fibers containing a metal oxide antibacterial agent, so that the antibacterial effect can be exerted from the early stages of excretion.
Moreover, as described above, the surface material 2 has an uneven structure with hollow convex portions 33, and the skin side ULa and non-skin side ULb of the upper layer UL that directly contacts the excrement of the hollow portions 10 and recesses 34 where excrement is likely to remain are comprised of fibers containing a metal oxide antibacterial agent that are kneaded so that the metal oxide antibacterial agent is likely to remain in the surface material 2. This allows the excrement remaining in the hollow portions 10 and recesses 34 to come into contact with the metal oxide antibacterial agent efficiently and frequently.
Therefore, even with a small content of the metal oxide antibacterial agent, the antibacterial effect can be efficiently and effectively exhibited, and the proliferation of bacteria caused by the wearer's excrement is suppressed from the early stage of excretion, thereby suppressing skin troubles.

In addition, since the surface material 2 is provided with the consolidated regions 52a, the antibacterial effect can be more efficiently and effectively exerted in the recesses 34. That is, as described above, the consolidated regions 52a constituting part of the recesses 34 and their vicinity are configured to easily draw in excrement from the wearer due to the difference in fiber density with the surrounding areas, and liquid excrement is less likely to permeate the consolidated regions 52a and their vicinity, making it easier for excrement to accumulate in the recesses 34. This allows efficient contact between the metal oxide antibacterial agent and excrement.
In the compressed region 52a formed by the compression process involving melting of the fiber material, the original fiber form of the surface material may be lost and the surface material may become a film. The compressed region 52a in such a film-like state is less permeable to excrement and more likely to accumulate in the recesses 34, allowing more efficient contact between the metal oxide antibacterial agent and the excrement.

In this way, the surface material 2 of this embodiment has an uneven structure with hollow parts, which makes it easy for excrement to remain on the surface material, and the metal oxide antibacterial agent is blended into the surface material so that the excrement and the metal oxide antibacterial agent come into contact with each other frequently in the areas where the excrement remains. This makes it possible to efficiently exert the antibacterial effect, and an excellent antibacterial effect can be obtained with a small amount of the metal oxide antibacterial agent.
Furthermore, in the surface material 2, since it is possible to exert an efficient antibacterial effect without distributing a metal oxide antibacterial agent throughout all layers constituting the surface material, the content of the metal oxide antibacterial agent can be kept low.
Here, metal oxide antibacterial agents not only act on excrement-derived bacteria that cause skin rashes, but also on the normal bacteria on the skin that help the skin's barrier function, potentially disrupting the balance of normal bacteria on the skin and causing skin problems.
However, in the surface material 2 of the present embodiment, the content of the metal oxide antibacterial agent can be kept low while still obtaining a sufficient antibacterial effect, so that the balance of the normal bacteria on the skin is not disturbed by an excessive amount of the metal oxide antibacterial agent, skin troubles are effectively suppressed, and costs can be reduced.

[About the upper layer]
As described above, in the surface material 2 of this embodiment, the upper layer UL has a multi-layer structure consisting of two layers, the first layer 21 and the second layer 22 .
The upper layer UL may be a single layer or a multi-layer structure of three or more layers. When the upper layer UL is a multi-layer structure, the layer constituting the skin side ULa and the layer constituting the non-skin side ULb of the upper layer UL may each contain a fiber containing a metal oxide antibacterial agent. This results in the skin side ULa and the non-skin side ULb containing a fiber containing a metal oxide antibacterial agent.

In the surface material 2, the content ratio of the metal oxide antibacterial agent in each of the first layer 21 and the second layer 22 may be equal, but from the viewpoint of obtaining a sufficient antibacterial effect from the metal oxide antibacterial agent and reducing the amount of metal oxide antibacterial agent in the entire surface material 2 to easily maintain a good balance of normal bacteria on the skin, it is preferable that the first layer 21 has a higher content ratio of the metal oxide antibacterial agent than the second layer 22.
Here, the first layer 21 is a surface that can come into direct contact with the wearer's skin. The skin side 2a of the surface material 2 formed by the first layer 21 has an uneven structure, which reduces the contact area between the skin and the surface material 2 and suppresses rubbing of the skin by the surface material 2. On the other hand, the uneven structure tends to reduce the chance of contact between bacteria derived from excrement attached to the skin and the metal oxide antibacterial agent.
In contrast, in the surface material 2 of this embodiment, by configuring the first layer 21 in the upper layer UL to have a relatively high content of metal oxide antibacterial agent, it is possible to ensure a sufficient opportunity for contact between bacteria derived from excrement and the metal oxide antibacterial agent, even with an uneven structure, and to obtain a sufficient antibacterial effect. On the other hand, it is sufficient that the second layer 22 contains a metal oxide antibacterial agent to an extent that the excrement present in the hollow portion 10 is sufficiently antibacterial, and the content of the metal oxide antibacterial agent can be relatively lower than that of the first layer 21.
In this way, by making the first layer 21 of the surface material 2 contain a higher proportion of metal oxide antibacterial agent than the second layer 22, it is possible to obtain a sufficient antibacterial effect from the metal oxide antibacterial agent while reducing the amount of metal oxide antibacterial agent in the entire surface material 2, making it easier to maintain a good balance of resident bacteria on the skin.

In the surface material 2 of this embodiment, by constructing the upper layer UL in a multi-layer structure, the content ratio of the metal oxide antibacterial agent contained in each of the skin side ULa and non-skin side ULb of the upper layer UL can be easily adjusted.
That is, when the upper layer UL has a multi-layer structure, the content ratio of the metal oxide antibacterial agent in each of the layers constituting the skin side ULa and the non-skin side ULb of the upper layer UL can be easily adjusted by varying the content ratio of the metal oxide antibacterial agent in each of the layers constituting the skin side ULa and the non-skin side ULb of the upper layer UL. This makes it easy to adjust the distribution of the metal oxide antibacterial agent in the surface material 2 so as to obtain a sufficient antibacterial effect while reducing the amount of the metal oxide antibacterial agent in the entire surface material 2.

[About the lower layer]
As described above, the lower layer LL (third layer 23) may or may not contain fibers containing a metal oxide antibacterial agent.
In the surface material 2 of this embodiment, the lower layer LL has a single layer structure, but may have a multi-layer structure in which two or more layers are laminated. When the lower layer LL has a multi-layer structure, it is configured to include a third layer 23 that constitutes the skin side LLa. The third layer may or may not contain a fiber containing a metal oxide antibacterial agent.

[Relationship between the content ratios of metal oxide antibacterial agents in the first layer, second layer, and third layer]
In addition to the first layer 21 having a higher content of metal oxide antibacterial agent than the second layer 22 , the second layer 22 may also have a higher content of metal oxide antibacterial agent than the third layer 23 .
In other words, in the surface material 2, of the three layers (first layer 21, second layer 22, third layer 23) constituting the surface material 2, the content ratio of the metal oxide antibacterial agent in the third layer 23, which is located closest to the skin, may be the lowest.
In the surface material 2 of this embodiment, the content of metal oxide antibacterial agent is highest in the first layer 21, followed by the second layer 22, and the third layer 23, which has the lowest content of metal oxide antibacterial agent.

With this configuration, an efficient and effective antibacterial effect can be obtained, and by reducing the content of the metal oxide antibacterial agent in the entire surface material 2, it becomes easier to maintain a good balance of normal bacteria on the skin.
That is, in the surface material 2, the metal oxide antibacterial agent is contained in the skin side surface ULa and the non-skin side surface ULb of the upper layer UL, so that the metal oxide antibacterial agent can come into frequent contact with excrement that accumulates in the hollow portion 10 formed by the non-skin side surface ULb of the upper layer UL and the recess 34 formed by the skin side surface ULa. Therefore, in the surface material 2, a sufficient antibacterial effect can be obtained even if the content of the metal oxide antibacterial agent in the third layer 23 is relatively low. Therefore, by lowering the content of the metal oxide antibacterial agent in the third layer 23, the amount of the metal oxide antibacterial agent in the entire surface material 2 can be reduced, making it easier to maintain a good balance of normal bacteria on the skin.

In the surface material 2 of this embodiment, from the viewpoint of efficiently and effectively exerting the skin trouble prevention effect of the metal oxide antibacterial agent 6 and further maintaining the balance of normal bacteria on the skin to suppress skin troubles, the preferred content ratios of the metal oxide antibacterial agent in each of the first layer 21, second layer and third layer 23 are as follows: A method for calculating the content ratio of the metal oxide antibacterial agent in each layer will be described later.
In the first layer 21, the content of the metal oxide antibacterial agent is preferably 0.04% by mass or more and 2.5% by mass or less, and more preferably 0.05% by mass or more and 2.0% by mass or less.
In the second layer 22, the content of the metal oxide antibacterial agent is preferably 0.025% by mass or more and 2.25% by mass or less, and more preferably 0.045% by mass or more and 1.25% by mass or less.
In the third layer 23, the content of the metal oxide antibacterial agent is preferably 0% by mass or more and 1.25% by mass or less, and more preferably 0.01% by mass or more and 1.25% by mass or less.

[Content of metal oxide antibacterial agent-containing fiber in each of the first layer, second layer, and third layer]
The content ratio of the metal oxide antibacterial agent in each of the first layer 21, the second layer 22, and the third layer 23 can be adjusted, for example, by adjusting the content ratio of the metal oxide antibacterial agent-containing fiber in each layer, so as to satisfy the relationship of the content ratio of the metal oxide antibacterial agent in the first layer, the second layer, and the third layer described above.

In the surface material 2 of this embodiment, the preferred content ratios of the metal oxide antibacterial agent-containing fibers in each of the first layer 21, the second layer 22, and the third layer 23 are as follows.
In the first layer 21, the proportion (content) of the fibers containing a metal oxide antibacterial agent among the fibers constituting the first layer 21 is preferably 80 to 100% by mass from the viewpoint of efficient and effective antibacterial activity on the skin side 2a. In this embodiment, the content of the fibers containing a metal oxide antibacterial agent in the first layer 21 is 100% by mass.
In the second layer 22, the proportion (content) of the fibers containing a metal oxide antibacterial agent among the fibers constituting the second layer 22 is preferably 50 to 90% by mass, from the viewpoint of efficient and effective antibacterial expression in the hollow portion 10 and maintaining a good balance of normal bacteria on the skin. In this embodiment, the content of the fibers containing a metal oxide antibacterial agent in the second layer 22 is 85% by mass.
In the third layer 23, the proportion (content) of the fibers containing a metal oxide antibacterial agent among the fibers constituting the third layer 23 is preferably 0 to 50 mass % from the viewpoint of maintaining a good balance of normal bacteria on the skin. In this embodiment, the content of the fibers containing a metal oxide antibacterial agent in the third layer 23 is 0 mass %.

[Proportion of metal oxide antibacterial agent in the entire surface material]
From the viewpoint of efficiently and effectively exerting the skin trouble prevention effect of the metal oxide antibacterial agent 6 and further maintaining the balance of normal bacteria on the skin to suppress skin troubles, the proportion (content) of the metal oxide antibacterial agent in the entire surface material is preferably 0.015 mass% or more and 2.0 mass% or less, and more preferably 0.04 mass% or more and 0.75 mass% or less.
The method for calculating the proportion of the metal oxide antibacterial agent in the entire surface material will be described later.

[Proportion of fibers containing metal oxide antibacterial agents in the entire surface material]
For example, by adjusting the proportion (content) of the fibers containing the metal oxide antibacterial agent in the entire surface material, the proportion of the metal oxide antibacterial agent in the entire surface material can be set within the range shown above.
From the viewpoint of efficiently and effectively exerting the skin trouble prevention effect of the metal oxide antibacterial agent 6 and further maintaining the balance of normal bacteria on the skin to suppress skin troubles, the proportion of fibers containing the metal oxide antibacterial agent in the entire surface material is preferably 30 mass% or more and 80 mass% or less, and more preferably 40 mass% or more and 70 mass% or less.

[Fiber distance]
The first layer 21, the second layer 22, and the third layer 23 may have different fiber densities. In other words, the first layer 21, the second layer 22, and the third layer 23 may have different inter-fiber distances (gaps between fibers).
"Different fiber densities" means different inter-fiber distances. "High fiber density" means a state in which the inter-fiber distance is relatively small, and "low fiber density" means a state in which the inter-fiber distance is relatively large. A state in which the inter-fiber distance is small means a state in which the fibers are densely packed. A state in which the inter-fiber distance is small has a greater capillary force for drawing liquid than a state in which the inter-fiber distance is large.

From the viewpoint of exerting the antibacterial effect by the metal oxide antibacterial agent more efficiently, in the surface material 2, it is preferable that the first layer 21 has a relatively smaller inter-fiber distance than the second layer 22, and the second layer 22 has a relatively smaller inter-fiber distance than the third layer 23. In other words, it is preferable that the first layer 21 has the highest fiber density, the second layer 22 has the next highest fiber density, and the third layer 23 has the lowest fiber density.
With this configuration, excrement can be easily retained closer to the skin side ULa of the surface material 2 in the thickness direction Z of the surface material 2. This allows excrement to come into contact efficiently and frequently with the first metal oxide antibacterial agent-containing fiber 61 and the second metal oxide antibacterial agent-containing fiber 621 located closer to the skin side ULa.
More specifically, with the above-mentioned configuration, in the surface material 2, the first layer 21 has the largest liquid attraction force, followed by the second layer 22, and the third layer 23 has the smallest liquid attraction force. Since the first layer 21 has the largest liquid attraction force, the time during which the excrement remains in the recesses 34 can be more reliably secured. This allows the contact frequency between the metal oxide antibacterial agent and the excrement to be increased, enabling efficient antibacterial treatment. Furthermore, the excrement that has permeated the upper layer UL and migrated to the hollow portion 10 can more reliably secure the time during which the excrement remains temporarily in the hollow portion 10 due to the difference in liquid attraction force caused by the difference in the fiber-to-fiber distance between the second layer 22 and the third layer 23. This allows the contact frequency between the excrement in the hollow portion 10 and the metal oxide antibacterial agent to be increased, enabling efficient antibacterial treatment.

The inter-fiber distance of each layer can be adjusted, for example, by varying the fiber diameter of the fibers used in each layer. As an example, in the surface material 2 of this embodiment, the fiber diameter of the first metal oxide antibacterial agent-containing fiber 61 and the second metal oxide antibacterial agent-containing fiber 621 is set to 15 μm, and the fiber diameter of the second metal oxide antibacterial agent-free fiber 622 and the third metal oxide antibacterial agent-free fiber 63 is set to 20 μm, so that the inter-fiber distances of the first layer 21, the second layer 22, and the third layer 23 can be in the relationship described above.

When the upper layer UL and the lower layer LL each consist of one layer, it is preferable that the inter-fiber distance of the upper layer UL is relatively smaller than that of the lower layer LL in the surface material.
With this configuration, in the surface material 2, the upper layer UL has the greatest liquid attraction force, and the lower layer LL has the smallest. Since the upper layer UL has the greatest liquid attraction force, the time that the excrement remains in the recesses 34 can be more reliably secured, and the frequency of contact between the metal oxide antibacterial agent and the excrement can be increased, enabling efficient antibacterial treatment. Furthermore, for the excrement that has permeated the upper layer UL and migrated to the hollow portion 10, the difference in liquid attraction force due to the difference in the inter-fiber distance between the upper layer UL and the lower layer LL ensures that the excrement remains temporarily in the hollow portion 10 for a longer period of time, enabling efficient antibacterial treatment.

Specific numerical values of the inter-fiber distances in each of the first layer 21, the second layer 22, and the third layer 23 will be given below, but these are merely examples and are not limited to these.
In the surface material 2, from the viewpoint of more reliably ensuring the time that excrement remains in the recesses 34 and increasing the frequency of contact between the metal oxide antibacterial agent and the excrement, the inter-fiber distance in the first layer 21 is preferably 30 μm or more, more preferably 50 μm or more, preferably 100 μm or less, more preferably 80 μm or less, preferably 30 μm or more and 100 μm or less, more preferably 50 μm or more and 80 μm or less.
From the viewpoint of making it easier for the excrement that has migrated into the hollow portion 10 to remain temporarily within the hollow portion 10 and increasing the frequency of contact between the metal oxide antibacterial agent and the excrement, the difference between the inter-fiber distance in the second layer 22 and the inter-fiber distance in the third layer 23 is preferably 10 μm or more, and more preferably 20 μm or more.
The inter-fiber distance in the second layer 22 is preferably 40 μm or more, more preferably 60 μm or more, and preferably 110 μm or less, more preferably 90 μm or less, preferably 40 μm or more and 110 μm or less, more preferably 60 μm or more and 90 μm or less.
The inter-fiber distance in the third layer 23 is preferably 50 μm or more, more preferably 70 μm or more, and preferably 190 μm or less, more preferably 170 μm or less, preferably 50 μm or more and 190 μm or less, more preferably 70 μm or more and 170 μm or less.
The method for measuring the inter-fiber distance will be described later.

Solubility of Metal Oxide Antibacterial Agents
The metal oxide antibacterial agent kneaded into the fiber containing the metal oxide antibacterial agent is preferably poorly soluble in water, from the viewpoint of making the effect of preventing skin rash (skin trouble) caused by feces more pronounced for a long period of time. The solubility in water can be evaluated by the solubility obtained by the solubility measurement method described later.
The solubility of the metal oxide antibacterial agent is preferably 0.01 g/100 ml to 0.5 g/100 ml, more preferably 0.03 g/100 ml to 0.3 g/100 ml, and even more preferably 0.05 g/100 ml to 0.2 g/100 ml.

<Example of manufacturing method for surface material>
An example of a method for producing the surface material 2 will be given below, but the method is not limited to this.
The surface material 2, which has an uneven skin side 2a and a flat non-skin side 2b, can be produced by overlapping a nonwoven fabric made of a first metal oxide antibacterial agent-containing fiber 61, a laminate of a second metal oxide antibacterial agent-containing fiber 621 and a second metal oxide antibacterial agent-free fiber 622, and a nonwoven fabric made of a third metal oxide antibacterial agent-free fiber 63, and partially bonding these nonwoven fabrics.
A laminate of a nonwoven fabric made of a first metal oxide antibacterial agent-containing fiber 61 and a nonwoven fabric made of a laminate of a second metal oxide antibacterial agent-containing fiber 621 and a second metal oxide antibacterial agent-free fiber 622 constitutes the upper layer UL of the surface material 2.
The nonwoven fabric made of the third metal oxide antibacterial agent-free fibers 63 constitutes the lower layer LL of the surface material 2 .

As an example of the manufacturing method, the manufacturing method described in JP-A-2004-174234 can be used.
That is, the sheet-like material of the nonwoven fabric to be the upper layer UL is intermittently stretched and processed to have an uneven shape by being interlocked between two gear rolls having an uneven peripheral surface that mesh with each other. In the sheet-like material processed to have an uneven shape in this way, the stretched portion forms the convex portion 33. On the other hand, the non-stretched portion forms the concave portion 34 when it is made into a surface material 2. The sheet-like material to be the upper layer UL on which the multiple convex portions 33 are formed is superimposed on the sheet-like material to be the lower layer LL, and the superimposed material is pressed between two rolls, at least one of which is heated to a predetermined temperature, and partially bonded. As a result, the upper layer UL and the lower layer LL are consolidated and partially bonded by heat fusion in the consolidated region 52a (part of the concave portion 34), and the surface material 2 having an uneven structure is manufactured. The surface of the surface material 2 on the upper layer UL side (skin side 2a) has an uneven shape, and the surface of the surface material 2 on the lower layer LL side (non-skin side 2b) is almost flat.

<Additional information>

[Method of confirming that the part is hollow]
Whether the surface material has projections and recesses and the projections have hollow portions can be confirmed by cutting the surface material with a razor (e.g., a single-edged razor manufactured by Feather Safety Razor Co., Ltd.) to obtain a test piece and observing the cut surface of the test piece under magnification.
For example, the cut surface of the test piece is observed using a Hitachi S-4000 field emission scanning electron microscope, with the magnification adjusted so that all layers fit within the field of view.
When observing the cut surface, by simultaneously imaging objects of known dimensions, it is possible to determine the dimensions of each component, such as the height of the protrusion 33 and the thickness of each layer.
From the observation of the cut surface, it can be confirmed that the surface material is composed of laminated layers with different inter-fiber distances.
From the observation of the cut surface, it is possible to grasp not only the cross-sectional profile of the fiber but also the fiber structure, for example, whether the fiber is a sheath-core type fiber or a single fiber structure. Furthermore, in the case of a sheath-core type fiber, the area ratio of the core and the sheath can be calculated from the observation of the cut surface.
Observation of the cut surface confirmed the presence of the metal oxide antibacterial agent in the fiber, that the metal oxide antibacterial agent was disposed in the sheath, and that the metal oxide antibacterial agent was exposed on the fiber surface.
Furthermore, by performing SEM-EDX analysis of the cross section of the fiber, it was possible to confirm that the agent contained in the sheath was zinc oxide (a metal oxide antibacterial agent).

[Method of calculating the content ratio of metal oxide antibacterial agent in the first layer, second layer, and third layer]
Weigh out 1 g of the target layer (first, second or third layer) of the surface material, chop it into as small pieces as possible, and place it in a 300 ml beaker. Add 200 ml of ion-exchanged water to the beaker and stir with a magnetic stirrer so that the fibers are completely in contact with the water. While stirring the liquid, gradually add 3 ml of concentrated hydrochloric acid (about 10 M), and stir for another hour to elute the metal oxide antibacterial agent present on the surface of the fibers that make up the target layer. Next, add 6 ml of 5.1 M sodium hydroxide aqueous solution to neutralize the liquid, and then add 10 ml of a pH 10.7 buffer solution (containing 54.7 ml of 28% _NH3 aqueous solution and 0.535 g of _NH4Cl dissolved in ion-exchanged water) to finely adjust the pH.
Next, Eriochrome Black T reagent (0.125 g of Eriochrome Black T powder and 1.125 g of hydroxylamine hydrochloride dissolved in 25 ml of absolute ethanol) is added as an indicator to turn the liquid pale pink. Titration is performed using 0.0002 M EDTA.2Na as the titrant, and the amount (ml) of the titrant added when the liquid changes color from pink to pale blue to green is defined as the titration value A. Then, the mass of the metal oxide antibacterial agent is calculated using the following formula. In the formula below, "5,000,000" means the volume (ml) of the titrant per 1 mol.
Mass of metal oxide antibacterial agent (g) = titration value A x mass per mol of metal oxide antibacterial agent / 5,000,000
The mass of the metal oxide antibacterial agent calculated as above is the mass of the metal oxide antibacterial agent contained in 1 g of the target layer. Therefore, the calculated mass of the metal oxide antibacterial agent multiplied by 100 is the content of the metal oxide antibacterial agent in the target layer.

[Method of calculating the proportion of metal oxide antibacterial agent in the entire surface material]
As a target sample, 1 g of surface material was weighed out to include the first, second and third layers, and the proportion of the metal oxide antibacterial agent in the entire surface material was calculated using a method similar to that used to calculate the content of the metal oxide antibacterial agent in the first, second and third layers described above.

[Method for measuring interfiber distance]
The interfiber distance of a nonwoven fabric, which is a fiber assembly, is calculated by the following formula (1) based on the Wrotonowski assumption. The following formula (1) is generally used to calculate the interfiber distance of a fiber assembly. Under the Wrotonowski assumption, the fibers are cylindrical and are regularly arranged without crossing each other.
The surface material to be measured has a multi-layer structure including a first layer constituting a sparse region and a second layer constituting a dense region. The inter-fiber distances in each of the sparse region and dense region are calculated by the following formula (1).
In the calculation, the thickness t, basis weight W, fiber resin density ρ, and fiber diameter D used in the following formula (1) are those for the sparse region (first layer) and dense region (second layer) to be measured, respectively. The thickness t, basis weight W, and fiber diameter D are each the average values of the measured values at multiple measurement points.

The thickness t (mm) is measured by the following method. First, the surface material to be measured is cut into a piece of the surface material measuring 50 mm in the X direction and 50 mm in the Y direction. Next, the cut piece is placed on a flat plate, a flat glass plate is placed on top of it, and weights are evenly placed on the glass plate so that the load including the glass plate is 49 Pa. The thickness of the cut piece is then measured. The measurement environment is a temperature of 20±2°C, a relative humidity of 65±5%, and a microscope (Keyence Corporation, VHX-1000) is used as the measuring device. To measure the thickness of the cut piece, first, an enlarged photograph of the cut surface of the cut piece is obtained. An object of known dimensions is also photographed on this enlarged photograph. Next, a scale is fitted to the enlarged photograph of the cut surface of the cut piece, and the thicknesses of the coarse and dense regions of the cut piece are measured. The above operation is performed three times, and the average of the three measurements is taken as the thickness t of the layer to be measured.

In the cut surface of the cut piece, the coarse regions and dense regions are distinguished by the following method. The coarse regions have a lower density of constituent fibers (larger inter-fiber distance) than the dense regions, so in the cut surface of the cut piece, the regions with relatively large inter-fiber distances are coarse regions, and the regions with relatively small inter-fiber distances are dense regions. These two regions are distinguishable with the naked eye.

Basis weight W (g/ ^m2 ) is determined by cutting each of the coarse and dense regions of the surface material to be measured to a predetermined size (e.g., 12 cm x 6 cm), measuring the mass, and then dividing the measured mass by the area determined from the predetermined size ("basis weight W (g/ ^m2 ) = mass ÷ area determined from the predetermined size"). This measurement is repeated four times, and the average value is taken as the basis weight.

The resin density ρ (g/cm ³ ) of the fiber is measured using a density gradient tube in accordance with the density gradient tube method described in JIS L1015, Chemical Fiber Staple Test Method (URL: http://kikakurui.com/l/L1015-2010-01.html, or in a book, JIS Handbook Fibers-2000, (Japanese Standards Association), pp. 764-765).

The fiber diameter D (μm) was determined by measuring the cross sections of 10 fibers taken from each of the sparse and dense regions using a Hitachi S-4000 field emission scanning electron microscope, and the average value was used as the fiber diameter D (μm). The method for measuring the fiber diameter D was in accordance with the [Method for measuring fiber diameter] described below.

[Method of measuring fiber diameter]
The surface material of the object to be measured is cut with a razor (e.g., a single-edged razor manufactured by Feather Safety Razor Co., Ltd.) in the region other than the consolidated region to obtain a test piece having a rectangular shape in plan view. When cutting the object to be measured, care must be taken so that the structure of the cut surface of the test piece formed by the cutting is not destroyed by the pressure during cutting. A preferred method for cutting the object to be measured is to place the object to be measured in liquid nitrogen prior to cutting and thoroughly freeze it, and then cut it.
The test piece is attached to the sample stage using double-sided paper tape (Nichiban Co., Ltd., Uchistack NW-15). The test piece is then platinum-coated. An ion sputtering device E-1030 (product name) manufactured by Hitachi Naka Seiki Co., Ltd. is used for the coating, and the sputtering time is 30 seconds.
The cut surface of the test piece is observed at a magnification of 1000 times using a Hitachi S-4000 field emission scanning electron microscope.
Since the surface material has coarse and dense regions, the boundaries between the coarse and dense regions are identified from the difference in the interfiber distances in the electron microscope images, and the length of 10 fibers in the width direction relative to the longitudinal direction of the fiber is measured for each fiber present in each layer (coarse or dense region), and the average value is taken as the fiber diameter.

By observing the cut surface of the surface material, it is possible to determine whether the distance between fibers is relatively large or small, and to grasp the state of density in the surface material. Therefore, by observing the cut surface of the surface material, it is possible to confirm that the metal oxide antibacterial agent is present only in the dense regions.

[Method for measuring the solubility of metal oxide antibacterial agents]
5 g of the metal oxide antibacterial agent is added to 100 ml of water and stirred at 300 rpm for 30 minutes at room temperature (25° C.) Separately, the mass of the filter paper is measured, and the measured mass is regarded as the initial mass of the filter paper.
The stirred solution is filtered using the filter paper whose mass has been measured, and the filter paper is dried in a dryer at 40° C. for 2 hours. The mass of the dried filter paper is measured, and the measured mass is regarded as the dried mass of the filter paper. The solubility is then calculated using the following formula.
Solubility (g) = 5 (g) - {(mass of dried filter paper) (g) - (initial mass of filter paper) (g)}
A higher solubility calculated in this manner indicates a higher solubility in water, and a lower solubility indicates a lower solubility in water.

<Other embodiments>
Although the embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made without departing from the spirit of the present invention.

For example, in the above embodiment, a disposable diaper is shown as an example of an absorbent article, but the absorbent article is not limited to this. The absorbent article of the present invention may be, for example, a urine pad, a discharge sheet, a sanitary napkin, etc., and the surface material of the present invention can be used as the surface material of these absorbent articles. Absorbent articles are generally composed of a liquid-permeable surface material, a liquid-impermeable backing material, and a liquid-retaining absorbent interposed between the two sheets.

In addition, in each of the above-mentioned embodiments, the metal oxide antibacterial agent-containing fiber may contain antibacterial agents other than the metal oxide antibacterial agent, such as surfactants and organic compounds.

The metal oxide antibacterial agent-containing fiber may also contain a skin care agent.
As the skin care agent, a hydrophobic skin care agent, a hydrophilic skin care agent, etc. can be used.

A hydrophobic skin care agent is a hydrophobic component that is not water-soluble or water-dispersible or has extremely low solubility, and is a composition or compound that has protective, healing, etc. effects on the wearer's skin. More specifically, a hydrophobic component is one that dissolves in an amount of less than 1 g when 10 g of the component is mixed in 1 L of ion-exchanged water and then left to stand for 24 hours, preferably one that dissolves in an amount of 0.1 g or less, and particularly preferably one that does not dissolve at all.
Examples of hydrophobic skin care agents include fatty acids with a carbon chain length of 12 to 28 or ester compounds of such fatty acids and glycerin, wax, petrolatum, etc., and in particular, it is preferable to contain unsaturated fatty acids with a carbon chain length difference of 12 to 28 or glycerin ester compounds of such unsaturated fatty acids. The glycerin ester is a monoester, diester, or triester of glycerin and the above-mentioned unsaturated fatty acid, and in particular, a triester is preferable. As agents containing fatty acids or fatty acid compounds, natural product extracts such as argan oil and shea butter can be preferably used. In particular, argan oil, which is a hydrophobic vegetable oil containing unsaturated fatty acids, maintains the balance between moisture and oil in the skin, prevents dryness, and functions as a skin care agent. In addition, argan oil contains a large amount of unsaturated fatty acids such as oleic acid and linoleic acid, and has a strong ability to remove active oxygen, and can reduce skin damage caused by, for example, sunburn.

On the other hand, a hydrophilic skin care agent is a hydrophilic component that is water-soluble or water-dispersible, and is preferably capable of suppressing the occurrence of rash or inflammation, and, if rash or inflammation occurs, suppressing the progression of the rash or inflammation or alleviating the rash or inflammation. More specifically, a hydrophilic component is one that dissolves or disperses in an amount of 1 g or more when 10 g of the component is mixed in 1 L of ion-exchanged water and left to stand for 24 hours, preferably one that dissolves or disperses in an amount of 5 g or more, more preferably one that dissolves in an amount of 1 g or more, even more preferably one that dissolves in an amount of 5 g or more, and most preferably one that dissolves completely.
As the hydrophilic skin care agent, natural extracts such as peach leaf extract and witch hazel extract, polyhydric alcohols having 2 to 4 carbon chains, polyethylene glycol, hydrophilic compounds having skin care functions, etc. can be used.
Among these, peach leaf extract (hydrophilic extract), which is a plant extract, is preferred because it has antibacterial and anti-inflammatory properties. The peach leaf extract, which is a hydrophilic component, dissolves in the liquid supplied to the surface material and transfers to the skin, providing a skin care effect.
A polyhydric alcohol having 2 to 4 carbon chains is a hydrophilic component, typically 1,3-butylene glycol. The use of 1,3-butylene glycol improves the moisturizing effect and lubricity. The improved lubricity reduces friction between the skin and the nonwoven fabric, suppressing damage to the skin. 1,3-butylene glycol is a moisturizing liquid water-soluble base component that has a smooth feel and is less sticky, and keeps the skin moist. 1,3-butylene glycol is used as a moisturizing agent and also as a solvent. For example, when peach leaf extract is used as a skin care agent, 1,3-butylene glycol can be used as a solvent for the peach leaf extract. Here, 1,3-butylene glycol is used as an example, but any polyhydric alcohol having 2 to 4 carbon chains will have the same effect, and for example, propylene glycol may be used. Propylene glycol can also be used as an extraction solvent for peach leaf extract (hydrophilic extract).

The present invention can also have the following configuration.
＜1＞
A surface material for an absorbent article having a skin side having a plurality of protrusions and a plurality of recesses located between the plurality of protrusions, and a non-skin side,
an upper layer constituting the skin side and a lower layer constituting the non-skin side,
the protrusion has a hollow portion therein, the hollow portion being located between the upper layer and the lower layer;
A surface material for an absorbent article, wherein the fibers constituting the non-skin side of the upper layer that forms the hollow portion and the fibers constituting the skin side of the upper layer comprise metal oxide antibacterial agent-containing fibers, which are fibers containing a metal oxide antibacterial agent.
＜2＞
The metal oxide antibacterial agent-containing fiber is a fiber in which the metal oxide antibacterial agent is kneaded. The surface material for an absorbent article according to <1> above.
＜3＞
The surface material of the absorbent article according to the above item <1> or <2>, wherein the upper layer includes a first layer constituting the skin side and a second layer constituting the non-skin side.
＜4＞
The surface material for an absorbent article according to <3>, wherein the second layer has a lower content of the metal oxide antibacterial agent than the first layer.
＜5＞
the lower layer includes a third layer constituting a skin side surface of the lower layer,
The surface material of the absorbent article according to <4>, wherein the third layer has a lower content of the metal oxide antibacterial agent than the second layer.
＜6＞
The content ratio of the metal oxide antibacterial agent-containing fiber to the mass of each of the first layer, the second layer, and the third layer is
In the first layer, the content is 80% by mass or more and 100% by mass or less,
In the second layer, the content is 50% by mass or more and 90% by mass or less,
The surface material of the absorbent article according to <5>, wherein the third layer contains 0% by mass or more and 50% by mass or less.
＜７＞
The content ratio of the metal oxide antibacterial agent to the mass of each of the first layer, the second layer, and the third layer is
In the first layer, the content is preferably 0.04% by mass or more and 2.5% by mass or less, and more preferably 0.05% by mass or more and 2.0% by mass or less.
In the second layer, the content is preferably 0.025% by mass or more and 2.25% by mass or less, and more preferably 0.045% by mass or more and 1.25% by mass or less.
In the third layer, the content is preferably 0% by mass or more and 1.25% by mass or less, and more preferably 0.01% by mass or more and 1.25% by mass or less. The surface material of the absorbent article according to <5> above.
＜8＞
The surface material of an absorbent article described in any one of <5> to <7>, wherein the inter-fiber distance in the first layer is smaller than the inter-fiber distance in the second layer, and the inter-fiber distance in the second layer is smaller than the inter-fiber distance in the third layer.
＜9＞
The inter-fiber distance in the first layer is preferably 30 μm or more and 100 μm or less, more preferably 50 μm or more and 80 μm or less,
The inter-fiber distance in the second layer is preferably 40 μm or more and 110 μm or less, more preferably 60 μm or more and 90 μm or less,
The surface material for an absorbent article according to the above item <8>, wherein the inter-fiber distance in the third layer is preferably 50 μm or more and 190 μm or less, and more preferably 70 μm or more and 170 μm or less.
＜10＞
The surface material for absorbent articles according to the above item <8> or <9>, wherein a difference between an inter-fiber distance in the second layer and an inter-fiber distance in the third layer is preferably 10 μm or more, more preferably 20 μm or more.
<11>
The fiber containing a metal oxide antibacterial agent is a core-sheath type fiber having a core and a sheath, the sheath containing the metal oxide antibacterial agent, and the metal oxide antibacterial agent is exposed on a surface of the fiber containing the metal oxide antibacterial agent.
＜12＞
The surface material for absorbent articles according to the above item <11>, wherein a ratio of the metal oxide antibacterial agent in the core-sheath fiber is 0.05% by mass or more and 2.5% by mass or less.
＜13＞
The surface material of the absorbent article according to any one of <1> to <12>, wherein the metal oxide antibacterial agent is zinc oxide.
＜14＞
The surface material of the absorbent article according to any one of <1> to <13>, wherein the ratio of the metal oxide antibacterial agent-containing fiber to the entire surface material is 30 mass % or more and 80 mass % or less.
＜15＞
The surface material of the absorbent article according to any one of <1> to <13>, wherein the proportion of the metal oxide antibacterial agent in the entire surface material is 0.015 mass % or more and 2.0 mass % or less.
＜16＞
The surface material of the absorbent article according to any one of <1> to <15>, wherein the recess is formed by partially compressing the upper layer and the lower layer.
＜１７＞
An absorber;
and a surface material according to any one of <1> to <16>, which is located on the skin side of the absorbent body.

1... Disposable diapers (absorbent articles)
2...Surface material (surface material of absorbent article)
2a: Skin side of surface material 2b: Non-skin side of surface material 6: Metal oxide antibacterial agent 10: Hollow portion UL: Upper layer ULa: Skin side of upper layer ULb: Non-skin side of upper layer LL: Lower layer 33: Convex portion 34: Concave portion 61: First metal oxide antibacterial agent-containing fiber (metal oxide antibacterial agent-containing fiber)
621...second metal oxide antibacterial agent blended fiber (metal oxide antibacterial agent blended fiber)

Claims (13)

A surface material for an absorbent article having a skin side having a plurality of protrusions and a plurality of recesses located between the plurality of protrusions, and a non-skin side,
an upper layer constituting the skin side and a lower layer constituting the non-skin side,
the protrusion has a hollow portion therein, the hollow portion being located between the upper layer and the lower layer;
the fibers constituting the non-skin side of the upper layer forming the hollow portion and the fibers constituting the skin side of the upper layer include metal oxide antibacterial agent-containing fibers, which are fibers containing a metal oxide antibacterial agent;
the upper layer includes a first layer constituting the skin side and a second layer constituting the non-skin side,
the second layer has a lower content of the metal oxide antibacterial agent than the first layer;
the lower layer includes a third layer constituting a skin side surface of the lower layer,
the third layer has a lower content of the metal oxide antibacterial agent than the second layer;
the inter-fiber distance in the first layer is smaller than the inter-fiber distance in the second layer, and the inter-fiber distance in the second layer is smaller than the inter-fiber distance in the third layer;
Surface material for absorbent articles. The surface material for absorbent articles according to claim 1, wherein the metal oxide antibacterial agent-containing fiber is a fiber in which the metal oxide antibacterial agent is kneaded. The content ratio of the metal oxide antibacterial agent-containing fiber to the mass of each of the first layer, the second layer, and the third layer is
In the first layer, the content is 80% by mass or more and 100% by mass or less,
In the second layer, the content is 50% by mass or more and 90% by mass or less,
The surface material of the absorbent article according to claim 1 , wherein the third layer has a content of 0% by mass or more and 50% by mass or less. The content ratio of the metal oxide antibacterial agent to the mass of each of the first layer, the second layer, and the third layer is
In the first layer, the content is 0.04% by mass or more and 2.5% by mass or less;
In the second layer, the content is 0.025% by mass or more and 2.25% by mass or less;
The surface material of the absorbent article according to claim 1 , wherein the third layer has a content of 0% by mass or more and 1.25% by mass or less. The fiber-to-fiber distance in the first layer is 30 μm or more and 100 μm or less,
The fiber-to-fiber distance in the second layer is 40 μm or more and 110 μm or less,
The fiber distance in the third layer is 50 μm or more and 190 μm or less.
The surface material of the absorbent article according to claim 1. The difference between the fiber-to-fiber distance in the second layer and the fiber-to-fiber distance in the third layer is 10 μm or more.
A surface material for an absorbent article according to claim 1 or 5. 2. The surface material of an absorbent article according to claim 1, wherein the fiber containing a metal oxide antibacterial agent is a core-sheath type fiber having a core and a sheath, the metal oxide antibacterial agent is contained in the sheath, and the metal oxide antibacterial agent is exposed on the surface of the fiber containing the metal oxide antibacterial agent. The surface material for absorbent articles according to claim 7 , wherein the ratio of the metal oxide antibacterial agent in the core-sheath fiber is 0.05% by mass or more and 2.5% by mass or less. The facing of claim 1 , wherein the metal oxide antimicrobial agent is zinc oxide. The surface material for absorbent articles according to claim 1 , wherein the proportion of the fibers containing the metal oxide antibacterial agent in the entire surface material is 30% by mass or more and 80% by mass or less. The surface material of an absorbent article according to claim 1 , wherein the proportion of the metal oxide antibacterial agent in the entire surface material is 0.015% by mass or more and 2.0% by mass or less. The surface material for an absorbent article according to claim 1 , wherein the recess is formed by partially compressing the upper layer and the lower layer. An absorber;
An absorbent article comprising: a surface material according to claim 1 located on a skin side of the absorbent body.

Images