absorbent materials

Abstract

The present invention is an absorbent article having an elongated body comprising a top sheet on the skin side, a back sheet on the non-skin side opposite to the skin side, and an absorbent body disposed between the top sheet and the back sheet. The body has a low-density region at the rear of a buttock-facing area facing the wearer's buttocks when worn. This low-density region extends across the center line of the long side of the absorbent article and extends laterally. The entire low-density region is surrounded by a high-density region with a higher density than the low-density region.

Description

Technical Field

[0001] This invention relates to an absorbent article. Prior Technology

[0002] As absorbent articles such as sanitary napkins for menstrual use, products known for prolonged or overnight use have an extended back section that extends towards the buttocks. Various studies have been conducted on the construction of such absorbent articles to prevent leakage of bodily fluids from the back section. These studies also include the design of the absorbent body's shape.

[0003] For example, Patent Document 1 describes the following configuration: In an absorbent article having an absorbent core (absorbent body) with a shape that is longer in the front-to-back direction, the central region of the absorbent core has a protrusion that protrudes above the top surface of the side region. This protrusion is formed in such a way that it passes through a rear portion disposed behind the rear portion of the excretion section, which is arranged opposite to the excretion section of the wearer. [Previous Technical Documents] (Patent Documents)

[0004] Patent Document 1: Japanese Patent Application Publication No. 2014-104094 Summary of the Invention

[0005] [The problem the invention aims to solve]

[0006] However, in the conventional designs described above, there are still concerns regarding the following when wearing absorbent materials at night or for extended periods: depending on the way they are worn and the wearer's movements, the absorbent material facing the groin may not completely absorb bodily fluids, causing them to leak outwards along the groin towards the back or side (also known as lateral leakage). Therefore, there is a need to improve the fit to the buttocks, especially the fit to the back of the groin or areas further back than the groin, to prevent lateral leakage of bodily fluids.

[0007] In view of the above, one aspect of the present invention is to provide an absorbent article that improves the fit to the buttocks and prevents leakage. [Technical means to solve the problem]

[0008] One aspect of the present invention is an absorbent article having an elongated body, the body comprising a top sheet on the skin side, a back sheet on the non-skin side opposite to the skin side, and an absorbent body disposed between the top sheet and the back sheet, wherein the body has a low-density region at the rear of a buttock-facing region facing the wearer's buttocks when worn, the low-density region extending across the long side centerline of the absorbent article and extending laterally; the entire low-density region is surrounded by a high-density region with a higher density than the low-density region. [Effects of the invention]

[0009] According to one aspect of the present invention, an absorbent article is provided that improves fit to the buttocks and prevents leakage. Simple Explanation of the Diagram

[0010] Figure 1 is a plan view of one embodiment of the absorbent article of the present invention, viewed from the top side. Figure 2 is a cross-sectional view along line II of Figure 1. Figure 3 is a plan view showing the absorbent body of the absorbent article in Figure 1 exposed. Figure 4 is a magnified view of a portion of Figure 1. Figure 5 is a partial cross-sectional view of the absorber in Figure 4 along line II-II. Figure 6 is a diagram used to illustrate the formation of high-density and low-density regions. Figure 7 is an enlarged plan view of the high-density area. Figure 8 is the same as Figure 3, but it is used to illustrate the basis weight of the absorber. Implementation

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Furthermore, unless otherwise specified, identical or corresponding components in the drawings will be given the same symbols and their descriptions will be omitted.

[0012] <Basic Structure of Absorbent Materials> First, we will use sanitary napkins for nighttime or extended use as an example to illustrate the basic structure of absorbent articles. Figure 1 shows a plan view of absorbent article 1. Figure 2 shows a cross-sectional view taken along line II of Figure 1.

[0013] As shown in Figures 1 and 2, the absorbent article 1 has a liquid-permeable top sheet 3 positioned on the side facing the wearer's skin when worn, i.e., the skin side; and a liquid-impermeable back sheet 2 positioned on the non-skin side (underwear side) opposite to the skin side. Furthermore, an absorbent core 4 is disposed between the back sheet 2 and the top sheet 3. These back sheets 2, absorbent core 4, and top sheet 3 are layered to form a body (absorbent article body) 8. The absorbent core 4 is configured so that it is not exposed from the back sheet 2 and the top sheet 3 when viewed from above. Moreover, the edges of the back sheet 2 and the top sheet 3 can be joined at both ends along the long side direction D1 using adhesives, heat sealing, or the like.

[0014] The absorbent material 1, as shown in the figure, is a long, narrow, pad-like shape (with a relatively small thickness compared to its width and length). In this specification, the long side direction (front-to-back direction) of the absorbent material 1 is designated as D1, and the horizontal direction (left-to-right or width direction) perpendicular to the long side direction D1 is designated as D2. The long side direction D1 corresponds to the front-to-back direction of the wearer's body when wearing the absorbent material 1; the horizontal direction D2 corresponds to the left-to-right direction of the body.

[0015] In the configurations shown in Figures 1 and 2, the body 8 has a top view shape that is approximately linearly symmetrical with respect to the center line (center line of the long side direction) CL extending in the long side direction D1. However, the shape of the body 8 does not necessarily have to be linearly symmetrical. Furthermore, the components other than the shape of the absorbent article 1 and the body 8 (including the thickness and density of the absorbent body 4, the size and position of the compression groove, the shape and size of the flap extending from the body 8 in the lateral direction D2, etc.) can also be approximately symmetrical with the center line CL as the axis of symmetry, or they can be asymmetrical.

[0016] The backing sheet 2 can be a sheet material that is at least water-resistant, such as a sheet material made of olefin resins such as polyethylene or polypropylene. Alternatively, it can be a laminated sheet in which non-woven fabric is laminated onto a polyethylene sheet, and a non-woven fabric layered thereon to ensure substantial liquid impermeability via a waterproof membrane. Furthermore, from the viewpoint of preventing stuffiness, it is more desirable to use a sheet material that is both water-resistant and breathable. Such a water-resistant and breathable sheet material can be a multi-porous sheet obtained by melting and mixing inorganic fillers in an olefin resin such as polyethylene or polypropylene, molding it into a sheet, and then extending it in one or both axial directions. The backing sheet 2 can be a sheet material having the same shape as the absorbent article 1.

[0017] Top sheet 3 is a permeable sheet that allows bodily fluids such as menstrual blood, vaginal discharge, and urine to pass through quickly. The top sheet 3 can be made of porous or non-porous nonwoven fabric or porous plastic sheet, etc. As raw material fibers constituting the nonwoven fabric, for example, olefins such as polyethylene and polypropylene can be used alone or in combination of two or more of the following materials: synthetic fibers such as polyester and polyamide; regenerated fibers such as rayon and cupro fiber; and blended fibers of these, as well as natural fibers such as cotton. Furthermore, processing methods for nonwoven fabrics include spunlace, spunbond, thermal bonding, meltblown, and needle punching. Among these processing methods, spunlace is preferred from the viewpoint that it can produce soft nonwoven fabrics, spunbond is preferred from the viewpoint that it can produce nonwoven fabrics with good drape, and thermal bonding is preferred from the viewpoint that it can produce fluffy and soft nonwoven fabrics. Furthermore, composite fibers such as core-sheath type fibers, side-by-side type fibers, and split type fibers, which have a high-melting-point fiber as the core and a low-melting-point fiber as the sheath, can also be used.

[0018] The absorbent 4 is not limited, as long as it is a material capable of absorbing and retaining bodily fluids; preferably, it comprises cotton-like pulp and a water-absorbing polymer. As the water-absorbing polymer, superabsorbent polymer powder (SAP), superabsorbent fiber (SAF), and combinations thereof can be used. As the pulp, examples include pulp composed of cellulose fibers such as chemical pulp derived from wood, dissolving pulp, rayon, and artificial cellulose fibers such as acetate. As the raw material for chemical pulp, hardwoods and softwoods can be used, but softwoods are more suitable due to their longer fiber length.

[0019] Furthermore, synthetic fibers may also be mixed into the absorbent 4. As synthetic fibers, fibers composed of two or more of the following materials can be used: polyolefins such as polyethylene or polypropylene; polyesters such as polyethylene terephthalate and polybutylene terephthalate; polyamides such as nylon; and copolymers of these. Additionally, composite fibers such as core-sheath type fibers, parallel type fibers, and split type fibers, with a high-melting-point fiber as the core and a low-melting-point fiber as the sheath, can also be used. Furthermore, hydrophilic agents can be used to surface-treat hydrophobic fibers, thereby adding affinity for body fluids. Preferably, the absorbent 4 is manufactured by fiber lamination or air-laid method.

[0020] The absorber 4 may also have a locally formed absorber compression portion (including a high-compression portion and a low-compression portion) that is recessed from the top sheet 3 to the back sheet 2 (described in detail below). Furthermore, the absorber 4 may also be covered with a covering sheet made of colored or uncolored (white) crepe paper or non-woven fabric to prevent folding and breakage or to prevent the spillage of polymer particles.

[0021] Side sheets 7, 7 are disposed on both sides of the absorbent article 1, that is, on the sides in the transverse direction D2, along the long side direction D1 on the skin side. The side sheets 7 can be made of raw materials that have undergone appropriate water-repellent or hydrophilic treatments, either overall or locally, to prevent the penetration of body fluids or to improve skin feel. The side sheets 7 are preferably nonwoven fabrics containing natural fibers, synthetic fibers, regenerated fibers, or fibers made of these. When the side sheets 7 are nonwoven fabrics, they can be hot-air nonwoven fabrics, spunlace nonwoven fabrics, spunbond nonwoven fabrics, meltblown nonwoven fabrics, etc. From the viewpoint that they are less prone to creases and wrinkles and are soft, thus improving skin feel, hot-air nonwoven fabrics are preferred. Alternatively, the side sheets 7 can be treated with water-repellent agents such as silicone-based or paraffin-based agents.

[0022] Side piece 7 can also be folded back inside in the transverse direction D2 to form a strip-like portion with multiple layers extending along the side of the main body 8. Furthermore, elastic telescopic members can be arranged in an elongated state between the multiple layers along the long side direction D1 to form wrinkles. The folding back and the formation of wrinkles in side piece 7 are omitted from the description in this specification and are also omitted from the illustrations.

[0023] The absorbent article 1 may have a fluid discharge outlet facing region C, which, when worn, faces the wearer's fluid discharge outlet (the illustrated example is the vaginal opening); an anterior region F, which is adjacent to the anterior of the fluid discharge outlet facing region C and extends to the front end of the absorbent article 1; a perineal facing region (middle region) M, which is adjacent to the posterior of the fluid discharge outlet facing region C and, when worn, faces the perineum of the wearer; and a buttocks facing region B, which is adjacent to the posterior of the perineal facing region M and extends to the rear end of the absorbent article 1, and, when worn, faces the buttocks of the wearer. The perineal facing region M and the buttocks facing region B are sometimes collectively referred to as the posterior region. The buttocks facing region B includes an anterior buttocks facing region B1, which is adjacent to the perineal facing region M; and a posterior buttocks facing region B2, which is adjacent to the posterior of the anterior buttocks facing region B1. The front buttock-facing area B1 mainly faces the groin (the groove of the buttocks), that is, the area facing the part including the anus. The rear buttock-facing area B2 can be the rear part of the groin or the part further back from the rear end of the groin, especially the part facing the boundary between the buttocks and legs further back than the groin (above when standing). In addition, the description of the orientation relationship between the areas of the body 8 and the wearer's body is only a general guideline within the general scope of the wearer wearing absorbent materials in the usual style of dressing when lying down.

[0024] The length of the long side D1 of the area C facing the body fluid discharge outlet can be 50-120 mm; the length of the long side D1 of the area B facing the buttocks can be 90-230 mm. Furthermore, according to this configuration, for example, the combined length of the perineal area M and the buttocks area B is preferably longer than the length of the long side D1 of the buttocks area B, which is greater than the length of the long side D1 of the area with the wing WF. Also, the length of the long side D1 of the anterior buttocks area (groin area) B1 can be 40-100 mm; the length of the long side D1 of the posterior buttocks area B2 can be 40-120 mm. Furthermore, the total length of the long side D1 of the absorbent article 1 can be 250-450 mm.

[0025] The absorbent article 1 may have a pair of flaps WF, WF, each extending outward in the lateral direction D2 from both sides of the area C opposite the fluid outlet. An anti-shifting material (not shown) may be provided on the non-skin side of the flaps WF, WF. When worn, the flaps WF, WF can be folded back towards the non-skin side, and the anti-shifting material is used to adhere them to the underwear, thus using the flaps WF, WF and the body 8 to hold the underwear in place. This securely fixes the absorbent article 1 to the underwear. The flaps WF, WF are formed by joining the outward extensions of the side panels 7, 7 in the lateral direction D2 to the outward extensions of the back panel 2 in the lateral direction D2.

[0026] Furthermore, a pair of buttock-holding pieces HF,HF can be formed, extending from the perineal opposing region M towards the buttock opposing region B, and extending outward in the lateral direction D2 from the side of the main body 8. The buttock-holding pieces HF,HF prevent leakage of bodily fluids behind the absorbent article 1 and increase the contact area with the buttocks, thereby making the entire absorbent article 1 less prone to shifting in the lateral direction D2, especially for underwear, and also stabilizing the wearing position of the absorbent article 1. The buttock-holding pieces HF,HF can also be formed by joining the lateral extensions D2 of the side pieces 7,7 and the lateral extensions D2 of the back piece 2.

[0027] <Specific Composition of the Absorber> Figure 3 shows a plan view of the absorbent article 1 from Figure 1 with the top sheet 3 and side sheets 7,7 removed, exposing the absorbent body 4. As shown in Figures 1 and 3, the body 8 has regions in the buttock-facing region B where the absorbent body 4 has locally different densities. More specifically, the absorbent body 4 has a low-density region 46 and a high-density region 45 surrounding the low-density region 46, which has a higher density, preferably a pulp density, than the low-density region 46. In this specification, the terms low density and high density refer to relative magnitudes of density, not specific densities. The pulp density of the low-density region 46 can be 40-90% of the pulp density of the high-density region 45, preferably 60-80%. Furthermore, the pulp density of the low-density region 46 is preferably 0.035-0.1 g / cm³, more preferably 0.05-0.08 g / cm³. The preferred pulp density in the high-density region 45 is 0.055~0.15 g / cm3, and more preferably 0.07~0.12 g / cm3.

[0028] The low-density area 46 is mainly located in the rear buttock-facing area B2, forming when worn opposite the back of the wearer's buttocks, or in an area closer to the upper body than the groin when lying down. Furthermore, as shown in Figures 1 and 3, the low-density area 46 is formed across the long side centerline CL and extends laterally to D2. This low-density area 46, when worn, faces the shallow depression near the rear end of the wearer's groin, or the almost flat skin surface further back than the groin. Due to its softness, the low-density area 46 can conform to the shape of the skin surface, thus fitting snugly against the skin and providing a comfortable wearing experience.

[0029] Additionally, a low-density region 46' with a lower density than the surrounding area can be formed in the region C opposite the self-liquid outlet, further forward than the low-density region 46. This forward low-density region 46' can be formed into a high-basicity portion 4H containing a relatively high pulp basis weight (described in detail later). In this configuration, as shown in FIG3, the area outside the low-density regions 46 and 46' becomes the high-density region 45.

[0030] Figure 4 shows an enlarged view of the low-density region 46 and its surrounding area of ​​the absorbent 4 in Figure 1. When worn, as bodily fluids move backward along the center line CL of the long side of the groin, as indicated by the white arrow in Figure 4, they transfer from the high-density region 45 to the low-density region 46. Here, generally speaking, liquids do not easily diffuse from the high-density absorbent to the low-density absorbent. Therefore, at the leading edge of the low-density region 46, the diffusion rate temporarily decreases, and the diffusion within the low-density region 46 does not progress rapidly backward, but rather relatively slowly and also in the lateral direction D2 (white arrow in Figure 4). Therefore, the absorbent 4 can be utilized throughout the lateral direction D2. Furthermore, because the absorbent 4 contains more gaps between the pulp particles, the low-density region 46 retains a larger volume of bodily fluids, further reducing the backward migration of bodily fluids. Therefore, the low-density region 46 can be considered a stopper, preventing further backward migration of bodily fluids and preventing leakage. Furthermore, even if the bodily fluid does not flow out along the groin, it can prevent bodily fluid that cannot be completely absorbed by the area C opposite the bodily fluid outlet from shifting backward within the absorbent body 4.

[0031] The method for forming regions of different densities (low-density region 46 and high-density region 45) is not particularly limited, but it is preferable to form them by compressing (or extruding) the pre-stage composite fiber used as absorber 4 in the thickness direction. In this case, high-density region 45 is the region that has been densified through compression, while low-density region 46 is the region that has not been substantially compressed (or extruded). "Substantially uncompressed (or extruded)" means that the compression process used to form high-density region 45 was not subjected to pressure in the thickness direction from the compression mold (also called a core embossing mold, detailed later). However, as long as the function of low-density region 46 in this embodiment is not impaired, low-density region 46 may have a compressed portion.

[0032] The low-density region 46 is shaped to extend across the center line CL in the long direction and into the horizontal direction D2, and can also bend backward into a convex shape. In the illustrated example, the low-density region 46 is cashew-shaped (a curved strip with rounded ends, or a shape formed by bending the area near the center of the major axis of an ellipse towards one side of the major axis). In this way, by making the low-density region 46 convex backward, it can prevent fluid from shifting backward by wrapping around the area near the center in the horizontal direction D2, and thus can also effectively block fluid that deviates from the long direction D1. Furthermore, by bending backward into a convex shape, the low-density region 46 and the surrounding area can naturally deform along the roundness of the buttocks.

[0033] The radius of curvature of the centerline (approximately the centerline curving along the transverse direction D2) of the low-density region 46 can be 13-35 mm, and at least 15-25 mm along the centerline CL in the long direction. This curvature of the low-density region 46 enhances its ability to effectively block bodily fluids and prevents natural deformation. Furthermore, the width (length of the transverse direction D2) a of the low-density region 46 can be 30-60 mm, preferably 40% or more of the transverse direction D2 length of the absorbent 4, and more preferably 60% or more. The length (length of the long direction D1) b of the low-density region 46 can be 10-30 mm. Further, the ratio (a / b) of the transverse direction D2 length of the low-density region 46 to the long direction D1 length can be 1.5-4.

[0034] As shown in Figure 4, the high-density region 45 includes a low-compression portion 42 of the absorber and high-compression portions 41, 41, ... of the absorber with a compression depth greater than that of the low-compression portion 42. In the illustrated example, the high-compression portions 41, 41, ... of the absorber are distributed in a dispersed manner. That is, a plurality of high-compression portions 41, 41, ... of the absorber are arranged at intervals. In the high-density region 45, the area other than the high-compression portions 41, 41, ... of the absorber is called the low-compression portion 42 of the absorber. By forming the high-compression portions 41, 41, ... of the absorber, the high-density region 45 is more reliably compressed in the thickness direction without becoming overly rigid, and even during use, the shape of the absorber 4 is not easily deformed or loosened.

[0035] Figure 5 schematically shows a cross-section obtained by cutting a portion of the absorbent body 4 along line II-II of Figure 4. As shown in Figure 5, high-density regions 45 and 45 are formed before and after the low-density region 46. The high-density regions 45 and 45 are compressed in the thickness direction, making their thickness smaller than that of the low-density region 46. As shown in Figure 5, when the low-density region 46 is relatively raised, the aforementioned function as a leakage prevention zone is enhanced. This function is to conform to the shape of the skin surface and fit snugly against the skin. Furthermore, the low-density region 46 is a highly flexible region, so it is less likely to cause discomfort even when the wearer is lying down. Moreover, as shown in Figure 5, the low-density region 46 is formed in the rear buttock-facing region B2, thus it can fit well against body parts with shallow groins or no groin. In addition, the symbols 11' and 12' in Figure 5 indicate the positions of compression grooves (also called fit embossing, detailed later) formed at least on the top sheet 3 and the absorbent body 4 in steps after the absorbent body manufacturing step.

[0036] Here, the formation of regions with different densities (high-density region 45 and low-density region 46) will be explained with reference to FIG6. In order to form a density difference according to position, for example as shown in FIG6(a), a compression mold 80 with an uneven surface is prepared, and this compression mold 80 is pressed onto the surface of the fiber body 4a with absorbent material. The compression mold 80 is provided with a recess 86 corresponding to the low-density region 46, and the region within the recess 86 is not compressed in the thickness direction. Furthermore, the surface around the recess 86 becomes a low-compression surface 82 corresponding to the low-compression portion 42 of the absorbent, and a plurality of high-compression protrusions 81, 81, ... corresponding to the high-compression portion 41 of the absorbent are formed at intervals in the low-compression surface 82. When the compression mold 80 is pressed onto the fiber body 4a, as shown in FIG6(b), the fiber body 4a is squeezed in the thickness direction by the low-compression surface 82, but the fiber body 4a within the recess 86 is not squeezed or is hardly squeezed. Therefore, the height of the fiber-buffered body 4a located within the recess 86 remains higher than the surrounding area, and high density does not occur or almost does not occur. Furthermore, a plurality of spaced high-compression protrusions 81, 81, ... protrude from the low-compression surface 82 toward the fiber-buffered body 4a, thus forming a deeper recess on the fiber-buffered body 4a at positions opposite to the high-compression protrusions 81, 81, ... Then, as shown in FIG6(c), when the compression mold 80 is removed, an absorbent body 4 (FIG. 5) is obtained, wherein a low-density region 46 is formed in the long side direction D1, sandwiched between the high-density regions 45, 45. Then, the high-density region 45 is obtained with the following configuration: absorbent high-compression regions 41, 41, ... dispersed within the absorbent low-compression portion 42.

[0037] Figure 7 shows a partially enlarged view of the high-density region 45 in Figure 4. As shown in Figure 7, a plurality of absorbent high-compression sections 41, 41, ... are arranged at intervals in the high-density region 45. The region without absorbent high-compression sections 41, 41, ... is a continuous extension of absorbent low-compression sections 42. In the example shown in Figure 7, the long side direction D1 of the absorbent article 1 is considered as the vertical direction, and the absorbent high-compression sections 41, 41, ... are arranged in an alternating pattern. The absorbent high-compression sections 41, 41, ... can also be formed in other arrangements, such as a grid pattern. When arranged in an alternating pattern as shown in the figure, even when the absorbent article 1 is subjected to the force from the two legs in the horizontal direction D2, the stress is easily dispersed in the long side direction D1, allowing the absorbent 4 to bulge towards the top plate 3 without twisting. In the staggered configuration, the distance px between the center of one absorber high compression section 41 and the center of the absorber high compression section 41 adjacent to it in the transverse direction D2 can be an average of 4~12mm, and the distance py between the center of one absorber high compression section 41 and the center of the absorber high compression section 41 adjacent to it in the long side direction D1 can be an average of 4~12mm.

[0038] A plurality of absorber high-compression portions 41, 41, ... may have the same top view shape and the same size. The absorber high-compression portions 41, 41, ... may contain absorber high-compression portions with different shapes, for example, as shown in Figure 7, two different shapes of first absorber high-compression portions 41A, 41A, ... and second absorber high-compression portions 41B, 41B, ... . In the example shown in Figure 7, the first absorber high-compression portions 41A, 41A, ... are circular, and the second absorber high-compression portions 41B, 41B, ... are elongated. Furthermore, rows of first absorber high-compression portions 41A, 41A, ... arranged at intervals along the long side direction D1 are alternately arranged with rows of second absorber high-compression portions 41B, 41B, ... arranged at intervals along the long side direction D1. More specifically, the outline 41Ar and the bottom surface 41Ab of the first absorber high-compression portion 41A are both circular. On the other hand, the outline 41Br of the high-compression portion 41B of the second absorber is an elongated hexagon, and the bottom 41Bb of the high-compression portion 41B of the second absorber is elliptical. For example, when forming the high-compression portions 41, 41, ... of the absorber, the shape of such an outline and the shape of the bottom can be adjusted by changing the shape of the high-compression protrusion 81 in the compression mold 80 used (Fig. 6).

[0039] Furthermore, as shown in Figure 7, the direction of the centerline of the elongated high-compression portion 41B of the second absorber (for example, its major axis direction if it is elliptical) can form an angle of 75° to 105° with the direction of the centerline of the adjacent high-compression portion 41B of the same shape in the transverse direction D2, preferably 90°. This way, even if the right side of the body 8 is pulled forward and the left side is pulled backward, stress is less likely to concentrate, and twisting is less likely to occur within the absorber 4.

[0040] Furthermore, the absorbent 4 may have a uniform basis weight across its entire surface, or it may have regions where the basis weight is locally increased or decreased. Additionally, as mentioned above, the absorbent 4 contains pulp and a water-absorbing polymer, and the basis weight of the water-absorbing polymer is preferably the same throughout the entire absorbent 4. In this case, the relative basis weights of the pulp are reflected in the relative basis weights.

[0041] To illustrate the weight distribution of the absorbent body 4, Figure 8 omits the illustrations of the highly compressible portions 41, 41, ... of the absorbent body in Figure 3 and instead shows a plan view of the different weights within the absorbent body 4. As shown in Figure 8, a high weight portion 4H, with increased weight, is formed in the center of the transverse direction D2 of the absorbent body 4 in the region C opposite the body fluid outlet. Furthermore, the continuous regions in the center of the transverse direction D2 of the perineal region M and the anterior buttocks region B1 can be low weight portions 4L, with reduced weight. In the illustrated example, the region other than the high weight portion 4H and the low weight portion 4L is a medium weight portion 4M, with a weight lower than the high weight portion 4H and a weight higher than the low weight portion 4L. The high weight portion 4H, the medium weight portion 4M, and the low weight portion 4L can each be a region with almost uniform weight. If the basis weights in the specified part or area are almost uniform, it means that even if there are places with slightly different basis weights, the difference between the basis weights in the specified part or area and the average basis weights is less than 20% of the average basis weights, preferably less than 10%, and even more preferably less than 5%.

[0042] The aforementioned low-density region 46 is formed within the rear buttock-facing region B2. Furthermore, the rear buttock-facing region B2 is the medium-basic weight region 4M, which can be a region with uniform basic weight. That is, the low-density region 46 and the surrounding high-density region 45 have the same pulp basic weight. The pulp basic weight of the rear buttock-facing region B2, after achieving uniformity, is preferably 250~600 g / m², more preferably 300~600 g / m², and even more preferably 400~500 g / m².

[0043] The basis weight is uniform in both the low-density region 46 and the high-density region 45 (see Figures 3 and 8). Therefore, the low density of the low-density region 46 is achieved through compression, such as the formation of the high-compression portions 41, 41, ... of the absorber, and does not need to be achieved during the fiber deposition of the absorber 4. Furthermore, according to this embodiment, the thickness of the low-density region 46 is greater than the thickness of the high-density region 45. In the absorber 4, the thickness of the low-density region 46 can be 40% to 90% of the thickness of the high-density region 45. Also, the thickness of the low-density region 46 of the absorber 4 can be 5 to 9 mm, and the thickness of the high-density region of the absorber 4 can be 3 to 7 mm.

[0044] <Compression Trench> As shown in Figures 1 and 2, the body 8 of the absorbent article 1 in this form can have compression grooves (also called fitting grooves) formed by compressing the top sheet 3 and absorbent body 4 from the side of the top sheet 3. These compression grooves have the function of introducing and retaining bodily fluids, thus helping to prevent the diffusion of bodily fluids or induce bodily fluids. In the illustrated example, the compression grooves can include a plurality of compression grooves (illustrated by symbols 10, 11, 12, and 13). The compression grooves can be formed to be linearly symmetrical about the center line CL of the long side of the absorbent article 1 when viewed from above, but they do not necessarily have to be linearly symmetrical. For example, the compression grooves can be formed by passing a laminated body composed of at least the top sheet 3 and absorbent body 4 between a pair of pressure rollers. In this case, a convex roller can be positioned on the side of the top sheet 3 of the laminated body; a flat roller can be positioned on the side of the absorbent body 4 of the laminated body; and the two rollers can clamp and pressurize the laminated body. Additionally, the compression groove may include a low-compression section and a high-compression section, which compresses the material at a higher pressure than that in the low-compression section. In the diagram, the high-compression section is indicated by black.

[0045] In the configuration shown in Figure 1, a pair of central compression grooves 10, 10 extend along the long side direction D1, mainly from the fluid discharge outlet opposing region C to the perineal opposing region M. The pair of central compression grooves 10, 10 are formed separately on both sides of the long side direction centerline CL. The pair of central compression grooves 10, 10 are configured not to overlap with the high base portion 4H. The separation distance between the pair of central compression grooves 10, 10 in the transverse direction D2 can be fixed or variable. For example, as shown in Figure 1, it can be set small near the boundary between the fluid discharge outlet opposing region C and the perineal opposing region M, then large again behind it, and decreasing further backward.

[0046] Behind the pair of central compression grooves 10, 10, a first rear compression groove (first compression groove) 11 is formed, which is isolated from the pair of central compression grooves 10, 10. Preferably, the first rear compression groove 11 is formed in the buttock-facing region B, mainly in the groin-facing region B1. The first rear compression groove 11 has a shape that is generally convex rearward. More specifically, the first rear compression groove 11 may include at least three convex rearward arc-shaped portions. Alternatively, the first rear compression groove 11 may have a U-shape overlapping the long side centerline CL, preferably having a shape that includes a horseshoe-shaped compression groove and a compression groove that branches off laterally and extends forward. Further, behind the first rear compression groove 11, a second rear compression groove (second compression groove) 12 is formed, which is isolated from the first rear compression groove 11. The second rear compression groove 12 is a groove extending along the transverse direction D2 and has a convex rearward shape. Furthermore, a front compression groove 13 is formed in front of the pair of central compression grooves 10, 10. In the example shown in Figure 1, the front compression groove 13 has a closed shape composed of compression grooves that bulge forward and bend with different radii of curvature.

[0047] Preferably, as shown in Figures 3 and 4, the first rear compression groove 11 is formed further forward than the low-density region 46, and the second rear compression groove 12 is formed further rearward than the low-density region 46. Therefore, the low-density region 46 is sandwiched between the first rear compression groove 11 and the second rear compression groove 12 when viewed from above. From the viewpoint of ensuring the flexibility of the low-density region 46, it is preferable that, as shown in Figures 3 and 4, the first rear compression groove 11 and the second rear compression groove 12 do not overlap with the low-density region 46. Furthermore, the formation positions of the first rear compression groove 11 and the second rear compression groove 12 are also indicated in Figure 5 as the predetermined formation position 11' of the first rear compression groove 11 and the predetermined formation position 12' of the second rear compression groove 12.

[0048] The low-density area 46 is formed behind the buttock-facing area B2, which, when worn, faces the area near the wearer's buttocks where the curvature increases, thus bending significantly along its long side. At this time, the more flexible low-density area 46 is subjected to compressive forces from the first rear compression groove 11 and the second rear compression groove 12, thereby deforming by bulging outwards from the top plate 3. Therefore, by having the first rear compression groove 11 and the second rear compression groove 12, the fit for areas with shallow or almost no groin is improved.

[0049] Furthermore, the curvature of the convex shape, particularly the rearmost part, in the first rear compression groove 11, the curvature of the low-density region 46 (the curvature of the centerline L), and the curvature of the second rear compression groove 12 can be made smoother in sequence. That is, at the centerline CL in the long side direction, the radius of curvature of the centerline of the rearmost convex shape of the first rear compression groove 11, the radius of curvature of the aforementioned centerline L of the low-density region 46, and the radius of curvature of the centerline of the second rear compression groove 12 can increase as they move rearward. In this way, the rear buttock-facing region B2 can be made to fit snugly along the shape of the rear of the buttocks without wrinkles or folds.

[0050] Furthermore, by providing the first rear compression groove 11 and the second rear compression groove 12, the flow of bodily fluids to the rear or oblique rear can be blocked, thereby improving the function of preventing leakage. Also, the first rear compression groove 11 and the second rear compression groove 12 can also serve as the base points for bending when the body 8 bends three-dimensionally along the buttocks, thus improving the fit of the entire buttocks.

[0051] The present invention has been described above based on its embodiments, but the present invention is not limited to these embodiments. Furthermore, the above embodiments can be modified, replaced, added, deleted, and combined in various ways within the scope of the patent application, and these modifications also fall within the technical scope of the present invention.

[0052] Furthermore, the specific features of the present invention are described below.

[0053] (Postscript 1) Regarding the form of Appendix 1, it is an absorbent article having an elongated body, which includes a top sheet on the skin side, a back sheet on the non-skin side opposite to the skin side, and an absorbent body disposed between the top sheet and the back sheet. The body has a low-density area at the rear of the buttock-facing region facing the wearer's buttocks when worn. This low-density area extends across the center line of the long side of the absorbent article and extends laterally. The entire low-density area is surrounded by a high-density area with a higher density than the low-density area.

[0054] Based on the description in Appendix 1 above, the low-density area is formed at the rear of the area opposite the buttocks, allowing it to face the area near the rear of the wearer's groin or even further back than the groin when worn. Due to its higher softness, the low-density area can adhere closely to the shallow or almost non-existent depressions of the skin at the rear of the groin, improving the fit. Furthermore, when bodily fluids move backward along the groin towards the low-density area, they do not easily diffuse from the high-density area to the low-density area, thus reducing the diffusion rate before reaching the low-density area. Moreover, bodily fluids entering the low-density area diffuse relatively slowly backward and laterally, thus allowing for lateral utilization of the absorbent material. Additionally, the low-density area has more gaps between the pulp particles, thus retaining a relatively large amount of bodily fluid. In this way, the low-density area can be considered a barrier to prevent leakage.

[0055] (Postscript 2) Regarding the state in Appendix 2, the aforementioned high-density region is the region that has been high-densityened through compression.

[0056] Based on the above description of Appendix 2, the high-density region is formed by a relatively simple compression method, thus preventing the manufacturing process from becoming complicated. By preparing compression molds corresponding to both the low-density and high-density regions, it is possible to use an absorbent with uniform basis weight to achieve high density in desired regions and to obtain low-density regions without achieving high density in desired regions. Furthermore, by forming high-density regions within the absorbent, the shape retention of the absorbent is improved, preventing accidental dispersion of the absorbent.

[0057] (Note 3) Regarding the state of Appendix 3, the aforementioned buttock-facing region includes a basis weight homogeneous region where the pulp basis weight of the aforementioned absorbent is almost uniform, and the aforementioned low-density region is partially formed within the aforementioned basis weight homogeneous region.

[0058] Based on the above-mentioned sample in Appendix 3, the pulp basis weight is uniform in both the low-density and high-density regions, thus allowing for an increase in the thickness of the low-density regions. Furthermore, it eliminates the need for localized density adjustments in the low-density regions during absorber fiber accumulation, preventing complication of the manufacturing process.

[0059] (Postscript 4) Regarding the state of Appendix 4, the aforementioned low-density region has a shape that bulges backward.

[0060] Based on the above description of Appendix 4, the low-density area can be sealed in a way that surrounds the posterior end of the groin from the rear. Therefore, even if bodily fluids flow in a direction slightly deviating from the long side, leakage can be prevented more reliably.

[0061] (Note 5) Regarding the state of Appendix 5, at least on the aforementioned top sheet and the aforementioned absorber, a compression groove recessed from the side of the aforementioned top sheet is formed. The aforementioned compression groove includes a first compression groove extending in the lateral direction toward the front of the aforementioned low-density region and a second compression groove extending in the lateral direction toward the rear of the aforementioned low-density region.

[0062] Based on the description in Appendix 5 above, when worn, when the rear area opposite the buttocks is bent along its long side, the softer, lower-density area is subjected to compressive force from the first and second compression grooves, allowing it to deform by bulging towards the top plate. This improves the fit of the body to areas with shallow or no groin. Furthermore, since the first and second compression grooves extend laterally, they also help to prevent fluids from shifting backward.

[0063] (Note 6) Regarding the state of Appendix 6, the aforementioned first compression groove and the aforementioned second compression groove are respectively shapes that include a rearward protrusion.

[0064] Based on the aforementioned state of Appendix 6, the transfer of bodily fluids toward the oblique rear or side can also be prevented by the first compression groove (first posterior compression groove) and the second compression groove (second posterior compression groove). Furthermore, when it is necessary to make the rear of the buttocks area extend along the entire buttocks, the body needs to be curved in three dimensions in both the longitudinal and lateral directions. However, by means of the shapes of the first and second compression grooves in this state, the aforementioned three-dimensional curvature can be naturally formed.

[0065] This application asserts priority based on Japanese Patent Application No. 2022-088310, filed on May 31, 2022, the entire contents of which are incorporated herein by reference.

[0066] 1: Absorbent products (menstrual pads) 2: Backing 3: Top film 4: Absorber 4H: High basis weight of the absorber 4L: Low basis weight portion of the absorber 4M: The central heavy part of the absorber 7: Side panel 8: Main body (the main body of the absorbent item) 10: Central compression trench 11: First rear compression trench 11': Predetermined position for the formation of the first rear compression trench 12: Second rear compression trench 12': Predetermined position for the formation of the second rear compression trench 13: Compression trench ahead 41: High-compression section of the absorber 41A: High-compression section of the first absorber 41B: High-compression section of the second absorber 42: Low-compression section of the absorber 45: High-density area 46: Low-density region (non-compressible part) 80: Compression mold 81: High compression protrusion 82: Low-compression surface 86: concave part B: Opposite area of ​​the buttocks B1: The area opposite the buttocks (the area opposite the groin). B2: Area opposite the buttocks C: Area opposite the body fluid excretion outlet CL: Centerline along the longer side D1: Long side direction D2: Horizontal direction F: Front area HF: Hip support tablets M: Middle area (area opposite the perineum) WF: Wing

[0067] Domestic storage information (please note in order of storage institution, date, and number) none Overseas storage information (please note in the order of storage country, institution, date, and number) none

Claims

1. An absorbent article having an elongated body comprising a top sheet on a skin-side, a back sheet on a non-skin-side opposite to the skin-side, and an absorbent body disposed between the top sheet and the back sheet, wherein, The aforementioned body has a low-density area at the rear of the buttock-facing region facing the wearer's buttocks when worn. This low-density area extends across the center line of the long side of the absorbent material and extends laterally. The entire low-density area is surrounded by a high-density area with a higher density than the low-density area. The high-density area is the area that has been compressed to increase its density.

2. The absorbent article as described in claim 1, wherein, The aforementioned buttock-facing region includes a basis weight homogeneous region where the pulp basis weight of the aforementioned absorbent is almost uniform, and the aforementioned low-density region is partially formed within the aforementioned basis weight homogeneous region.

3. An absorbent article as described in claim 1 or 2, wherein, The aforementioned low-density region has a shape that bulges backward.

4. An absorbent article as described in claim 1 or 2, wherein, Compression grooves are formed on at least the aforementioned top sheet and the aforementioned absorber, with the compression grooves including a first compression groove extending in the lateral direction toward the front of the aforementioned low-density region and a second compression groove extending in the lateral direction toward the rear of the aforementioned low-density region.

5. The absorbent article as described in claim 4, wherein, The aforementioned first compression groove and the aforementioned second compression groove are respectively shapes that include a rearward protrusion.

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