WO2004112669A1

WO2004112669A1 - Sanitary napkin

Info

Publication number: WO2004112669A1
Application number: PCT/JP2004/007668
Authority: WO
Inventors: Noritatsu Tamagawa; Masataka Kinoshita; Kazuya Nishitani; Toshiyuki Tanio
Original assignee: Uni-Charm Corporation
Priority date: 2003-06-20
Filing date: 2004-05-27
Publication date: 2004-12-29
Also published as: KR101118382B1; CN100427050C; JP4421223B2; TW200505397A; JP2005007075A; KR20060017738A; CN1697641A; MY141105A; US20040260263A1; US7708725B2; TWI243051B

Abstract

A sanitary napkin that is provided with large rear flaps (42) to effectively prevent liquid from leaking obliquely rearward. The rear flaps (42) are disposed rearward of fold-back flaps (41) to be wrapped around a crotch part of an undergarment. The rear flap (42) is of a shape spreading rearwardly from a starting point (45). With a pressure from the thighs acting forward of the starting point (45), leakage preventing walls (30) forward of the starting point (45) can be maintained in a rising state during wear. On the other hand, the leakage preventing walls (30) rearward of the starting point (45) may possibly fall outward. However, even if the leakage preventing walls (30) fall outward rearward of the starting point (45), they will never project out of the rear flaps (42). Accordingly, they hardly leave a stain on an undergarment.

Description

DESCRIPTION

SANITARY NAPKIN

CROSS REFERENCE TO THE RELATED APPLICATION

The present application has been filed with claiming priority based on Japanese Patent Application No. 2003-177363, filed on June 20, 2003.

Disclosure of the above-identified Japanese Patent Application is herein

incorporated by reference.

TECHNICAL FIELD

The present invention relates to a sanitary napkin suitable for nighttime use. More particularly, the invention relates to a sanitary napkin provided with rear flaps for widely covering a posterior part of the crotch and the buttocks.

BACKGROUND ART

For nighttime use, there have been known elongated sanitary napkins

with fold-back flaps in its front portion and rear flaps in its rear portion.

Fig. 8 is a top plan view showing a conventional sanitary napkin 101 of

this type with its skin-side surface directed upward.

The sanitary napkin 101 has a main body constructed to include: a

liquid-permeable topsheet located on the skin-side surface; a

liquid-impermeable backsheet located on the garment-side surface; and a

liquid absorbent layer disposed between the topsheet and the backsheet.

The main body has a front portion with fold-back flaps 102, 102 projecting from transversely opposing sides thereof and a rear portion with rear flaps 103, 103

projecting from the transversely opposing sides. The sanitary napkin 101 is

intended to be placed on an inner surface of an undergarment from a crotch

part to a back body and fixed to the inner surface of the undergarment through

a pressure-sensitive adhesive layer disposed on a garment-side surface of the

backsheet.

The fold-back flaps 102, 102 may be folded back to cover either side

edge of the crotch part of the undergarment and adhered to an outer surface of the crotch part through pressure-sensitive adhesive layers. The rear flaps 103, 103 may be placed on the undergarment in an unfolded state to extend

from a rear portion of the crotch part to the back body, wherein the garment-side surfaces of the rear flaps 103, 103 can be fixed to the inner surface of the undergarment through pressure-sensitive adhesive layers.

On the skin-side surface of the main body, leakage preventing walls 104, 104 are provided to extend longitudinally on each side of a longitudinal

centerline Oy-Oy. Each leakage preventing wall 104 is provided with

longitudinally extending elastic members for exerting an elastic contractive force between front and rear ends 105, 106. With the elastic contractive force,

the leakage preventing wall 104 is raised from the skin-side surface between

the front and rear ends 105, 106.

In the sanitary napkin 101 , a front region 107a between the fold-back

flaps 102, 102 is intended to face the vaginal opening, and an intermediate

region 107b is intended to face the perineum and the anus. In a rear region

107c, the sanitary napkin is deformed to rise along the longitudinal centerline

Oy-Oy for fit in the cleft of the buttocks. Sanitary napkins of this type are disclosed, for example, in the

following Patent Publications 1 and 2. In the sanitary napkin disclosed in the

Patent Publication 1 , since the rear ends 106, 106 of the leakage preventing

walls 104, 104 are located farther rearward than shown in Fig. 8, menstrual

blood discharged from the vaginal opening and trying to flow obliquely

rearward may be blocked.

[Patent Publication 1]

Japanese Unexamined Patent Publication No. 2001-95842 [Patent Publication 2] Japanese Unexamined Patent Publication No. H07-33314

When the undergarment is worn with the sanitary napkin 101 of Fig. 8 being adhered and fixed thereto, the inside of the wearer's thigh faces a region

extending over a length of 150 to 170 mm with center at a transverse reference line Ox-Ox of the sanitary napkin 101. Since the thighs exert a transverse clamping force on this region, the leakage preventing walls 104, 104 come into contact with the thighs, hardly falling transversely outward.

Rearward of a line Lx-Lx that is spaced 70-80 mm apart rearwardly

from the transverse reference line Ox-Ox, however, the leakage preventing

walls 104, 104 cannot come into contact with the thighs. Rearward of the line

Lx-Lx, moreover, the leakage preventing walls 104, 104 will be subjected to a

pressure from the buttocks. Therefore, the leakage preventing walls 104, 104

rearward of the line Lx-Lx tend to fall outward without being constrained by the

thighs.

In the conventional sanitary napkin 101 of Fig. 8, the rear flaps 103,

103 have side edges 103a, 103a that are located close to the leakage preventing walls 104, 104 on the line Lx-Lx. When the leakage preventing

walls 104, 104 fall transversely outward, therefore, they extend beyond the

side edges 103a, 103a, so that menstrual blood applied to the leakage

preventing walls 104, 104 may possibly adhere to the undergarment outside

the rear flaps 103, 103.

In the conventional sanitary napkin 101 of Fig. 8, furthermore, the side

edges 103a, 103a of the rear flaps 103, 103 are gently inclined away from the longitudinal centerline Oy-Oy. Therefore, if menstrual blood flows out of the

leakage preventing walls 104, 104 near the line Lx-Lx obliquely rearward as indicated by an arrow 109, the menstrual blood tends to leak out beyond the side edges 103a, 103a of the rear flaps 103, 103. This also results in leaving a stain on the undergarment.

The present invention has been worked out in view of the shortcomings in the prior art set forth above. It is therefore an object of the present invention to provide a sanitary napkin which can effectively prevent an

undergarment or the like from being stained with menstrual blood even if leakage preventing walls fall outward.

DISCLOSURE OF THE INVENTION

According to the present invention, there is provided a sanitary napkin

comprising: an elongated main body having a skin-side surface and a

garment-side surface and including a liquid absorbent layer; a pair of leakage

preventing walls disposed on the skin-side surface of the main body and

extending longitudinally of the main body in parallel with each other; and a

pressure-sensitive adhesive layer disposed on the garment-side surface of the main body for adhering to an inner surface of an undergarment,

the main body having a rear portion with rear flaps projecting from

transversely opposing sides thereof, each rear flap having a starting point from

which a width of the sanitary napkin starts to increase and a spreading portion

in which the width gradually increases rearward from the starting point,

each leakage preventing wall being composed of: a sheet that is fixed

to the skin-side surface of the main body to have a longitudinally extending rising base; and an elastic member that is so tensioned between longitudinal front and rear ends of the leakage preventing wall as to raise the sheet from

the skin-side surface, the rear end of the leakage preventing wall being located rearward of the starting point of the rear flap, wherein when developed transversely outward at a position between the starting point and the rear end, the sheet of the leakage preventing wall rearward of the starting point extends exclusively inside an edge of the rear

flap.

In the sanitary napkin, the leakage preventing walls forward of the

starting points hardly fall outward due to the presence of the thighs outside

thereof. On the other hand, the leakage preventing walls rearward of the

starting points tend to fall outward when a wearer lies on her back while

wearing the sanitary napkin. However, even if the leakage preventing walls

fall down, they never project out of the rear flaps, so that menstrual blood

applied to the leakage preventing walls can be prevented from adhering to the

undergarment.

In the present invention, it is preferred that when developed

transversely outward at a position spaced 80+ 10 mm apart rearwardly from a transverse reference line on which the sanitary napkin is intended to face a

center of the vaginal opening, the sheet of the leakage preventing wall extends

exclusively inside the edge of the rear flap. When an average woman (Asian

adult woman) wears the sanitary napkin, the leakage preventing walls do not

come into contact with the thighs if they are more than 80+ 10 mm apart

rearwardly from the center of the vaginal opening.

In the present invention, it is preferred that rearward of the spreading portion, the rear flap has an intermediate portion with a linear side edge extending longitudinally over a length equal to or greater than 60 mm. More preferably, the length is equal to or greater than 100 mm. In this sanitary

napkin, since the wide intermediate portion of the rear flap extends longitudinally over at least 60 mm, preferably at least 100 mm, menstrual blood leakage can effectively be prevented over a large area. The linear side edge may be parallel with a longitudinal centerline of the sanitary napkin or so

inclined as to come closer to the longitudinal centerline of the sanitary napkin rearwardly. In order to effectively prevent menstrual blood flowing obliquely

rearward from reaching the undergarment, W1/L1 is preferably equal to or

greater than 0.7, more preferably equal to or greater than 1 , where L1

represents a length from the starting point to a front end of the linear side edge

and W1 represents a width from the starting point to the front end of the linear

side edge.

In the present invention, the skin-side surface of the main body may

have an elongated main absorbent region that is surrounded by a compressed

groove and intended to face the wearer's body from the vaginal opening to the

cleft of the buttocks, wherein the main absorbent region has a rear end that is not spaced more than 20 mm apart longitudinally from the rear end of the

leakage preventing wall.

In the present invention, it is preferred that when fully developed transversely outward, the sheet of the leakage preventing wall has a maximum width of 20 to 50 mm from the rising base.

According to the present invention, the sanitary napkin may be larger than ever such that it has a length equal to or greater than 400 mm and a width equal to or greater than 180 mm between the linear side edges of the rear flaps, relieving anxiety the undergarment may be stained with menstrual blood during sleep.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood more fully from the detailed description given hereinafter and from the accompanying drawings of the preferred embodiments of the present invention, which, however, should not be taken to limit to the invention, but are for explanation and understanding only. In the drawings:

Fig. 1 is a perspective view showing a state where a sanitary napkin according to one embodiment of the present invention is placed on an undergarment;

Fig. 2 is a top plan view of the sanitary napkin; Fig. 3 is a top plan view of the sanitary napkin; Fig. 4 is a half sectional view taken along line IV-IV of Fig. 2;

Fig. 5 is a half sectional view taken along line V-V of Fig. 2;

Fig. 6 is a half sectional view showing a state where a leakage preventing wall according to another embodiment is raised;

Fig. 7 is a longitudinal sectional view showing a state where the

sanitary napkin is deformed; and

Fig. 8 is a top plan view of a conventional sanitary napkin.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention will be discussed hereinafter in detail in terms of the preferred embodiments according to the present invention with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present

invention. It will be obvious, however, to those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known structures are not shown in detail in order not to obscure the features of the present invention. It should be noted that the sanitary napkin, as well as its individual

components, has two major surfaces: of which one surface intended to be worn toward the wearer's crotch is referred to as "skin-side surface", while the other

surface is referred to as "garment-side surface". It should also be noted that

unless otherwise stated, the term "length" as used herein refers to a dimension

measured longitudinally of the sanitary napkin and the term "width" as used

herein refers to a dimension measured transversely of the sanitary napkin.

Fig. 1 is a perspective view showing a state where a sanitary napkin 1

according to a first embodiment of the present invention is placed on an

undergarment; Figs. 2 and 3 are top plan views of the sanitary napkin 1 ; Fig. 4

is a half sectional view taken along line IV-IV of Fig. 2; Fig. 5 is a half sectional view taken along line V-V of Fig. 2; Fig. 6 is a half sectional view showing a state where a leakage preventing wall according to another embodiment is raised; and Fig. 7 is a longitudinal sectional view showing a state where the sanitary napkin 1 is deformed during wear. According to the first embodiment shown in Figs. 1-5, the sanitary napkin 1 comprises: an elongated main body 2 having a skin-side surface 2a and a garment-side surface 2b; and a pair of leakage preventing walls 30, 30 that are allowed to rise from the skin-side surface 2a of the main body 2.

In Fig. 2, the sanitary napkin 1, which is slightly curved in Fig. 1, is shown in a fully opened (or flattened) state. Fig. 2 shows a longitudinal centerline Oy-Oy coinciding with midpoints of front and rear end edges 1a, 1b of the sanitary napkin 1, wherein the sanitary napkin 1 has bilateral symmetry about the longitudinal centerline Oy-Oy. Fig. 2 also shows a transverse reference line Ox-Ox on which the sanitary napkin 1 is intended to face the center of the vaginal opening during wear. In the present embodiment with fold-back flaps 41 , 41 , the transverse reference line Ox-Ox substantially coincides with a line which longitudinally bisects the fold-back flaps.

As shown in Figs. 4 and 5, a liquid-permeable topsheet 3 appears on the skin-side surface 2a of the main body 2 in a region between the leakage preventing walls 30, 30; a side sheet 4 appears outside each leakage

preventing wall 30. In the present embodiment, the side sheet 4 forms the leakage preventing wall 30. On the other hand, a liquid-impermeable

backsheet 5 appears on the garment-side surface 2b of the main body 2.

The main body 2 has a liquid absorbent layer 6 disposed between the topsheet 3 and the backsheet 5. As shown in Fig. 2, the liquid absorbent layer 6 is of an almost rectangular shape. The liquid absorbent layer 6 has a

front end edge 6a slightly inside the front end edge 1a of the sanitary napkin 1

and a rear end edge 6b slightly inside the rear end edge 1b of the sanitary

napkin 1. The liquid absorbent layer 6 has transversely opposite side edges

6c inside rising bases 31 of the leakage preventing walls 30. However, the

side edges 6c may be located outside the rising bases 31.

In the skin-side surface 2a, compressed grooves where the topsheet 3

and the liquid absorbent layer 6 are compressed are formed in the region between the leakage preventing walls 30, 30. The compressed grooves comprise: longitudinal compressed grooves 11 , 11 extending longitudinally in a curved manner; a front transverse compressed groove 12 located between

front portions of the longitudinal compressed grooves 11 , 11 ; and a rear transverse compressed groove 13 connecting rear portions of the longitudinal compressed grooves 11 , 11.

The region surrounded by the longitudinal compressed grooves 11 , 11 , the front transverse compressed groove 12, and the rear transverse

compressed groove 13 is referred to as elongated main absorbent region 10.

The main absorbent region 10 includes a front main absorbent region 10A, an

intermediate main absorbent region 10B, and a rear main absorbent region

10D.

In the front main absorbent region 10A, the right and left longitudinal

compressed grooves 11 , 11 are curved toward the longitudinal centerline

Oy-Oy, wherein the distance between the longitudinal compressed grooves 11,

11 is smallest near the transverse reference line Ox-Ox. In the intermediate

main absorbent region 10B, the longitudinal compressed grooves 11 , 11 are curved away from the longitudinal centerline Oy-Oy. The rear main absorbent

region 10D is elongated longitudinally of the napkin, in which the distance

between the longitudinal compressed grooves 11 , 11 is smaller than in the

intermediate main absorbent region 10B.

In the center absorbent region 10, a bulky, liquid permeable layer

(cushion layer) 7 of a lower density than the liquid absorbent layer 6 is

disposed between the topsheet 3 and the liquid absorbent layer 6, as shown in

Fig. 4.

Forward of the front transverse compressed groove 12 is provided a front outside compressed groove 14, as shown in Fig. 2. The front outside

compressed groove 14 is curved forward and connects the right and left longitudinal compressed grooves 11 , 11. The region surrounded by the front transverse compressed groove 12 and the front outside compressed groove 14

is referred to as front auxiliary absorbent region 15. Rearward of the rear transverse compressed groove 13 is provided a rear outside compressed groove 16. The longitudinal compressed grooves 11 , 11 , the rear transverse

compressed groove 13, and the rear outside compressed groove 16 are

connected together, and both the rear transverse compressed groove 13 and

the rear outside compressed groove 16 are curved rearward. Here, the

region surrounded by the rear transverse compressed groove 13 and the rear

outside compressed groove 16 is referred to as rear auxiliary absorbent region

17.

In the sanitary napkin 1 , the elongated region surrounded by the

longitudinal compressed grooves 11 , 11 , the front outside compressed groove

14, and the rear outside compressed groove 16 is raised higher than the remaining region outside it. Of the raised portion, the main absorbent region

10 is raised much higher.

On both right and left sides of the front main absorbent region 10A,

first outside longitudinal compressed grooves 21 , 21 are provided outside and

at a distance apart from the longitudinal compressed grooves 11 , 11. The

first outside longitudinal compressed grooves 21, 21 are also curved toward

the longitudinal centerline Oy-Oy, wherein the distance therebetween is

smallest near the transverse reference line Ox-Ox.

On both right and left sides of the rear main absorbent region 10D, second outside longitudinal compressed grooves 22, 22 are provided at a distance transversely apart from the longitudinal compressed grooves 11 , 11. The second outside longitudinal compressed grooves 22, 22 extend longitudinally in substantially parallel relation to the longitudinal centerline

Oy-Oy. It should be noted that they extend rearward from a boundary between the intermediate main absorbent region 10B and the rear main absorbent region 10D to have their rear ends farther rearward than the rear

outside compressed groove 16.

The individual compressed grooves are formed by heating the

topsheet 3 and the liquid absorbent layer 6 under pressure from the side of the

topsheet 3. At the bottoms of the individual compressed grooves,

high-density compressed portions (highly compressed portions) and

medium-density compressed portions (portions whose density is slightly lower

than the high-density compressed portions) alternate with each other along the

linear pattern of the compressed grooves so that the grooves are of a sufficient

depth overall. As shown in Figs. 4 and 5, the side sheet 4 has an edge 4a coinciding

with the outer edge of the backsheet 5. The side sheet 4 has a single-layer

portion and a multi-layer portion, wherein the single-layer portion is bonded to

the backsheet 5 or other materials disposed on the backsheet 5, whereas the

multi-layer portion forms the leakage preventing wall 30 (see Fig. 4) or a

stacked/fixed portion 37 (see Fig. 5). In the multi-layer portion, at first, the

side sheet 4 is folded on its fold line 4b to have an edge 4c on the topsheet 3. In Fig. 4, the side sheet 4 is bonded to the topsheet 3 from the rising base 31

to the edge 4c. Confronting surfaces of the side sheet 4 thus folded in two are bonded together through a hot-melt type adhesive with a plurality of elastic members 32, 33 disposed therebetween. The individual elastic members 32, 33 extend

longitudinally over the entire length of the leakage preventing wall 30 and beyond the front and rear ends 30a, 30b. The elastic members 32, 33 are bonded to the side sheet 4 while being longitudinally stretched to a

predetermined degree.

In an area of a length Lb from a rear bond edge 36 to the rear end

edge 1b (see Fig. 2), the multi-layer portion of the side sheet 4 previously

folded in two is further folded in three, as shown in Fig. 5, wherein these layers

are bonded to each other as well as to the topsheet 3, thereby forming the

stacked/fixed portion 37. Also in an area of a length Lc from a front bond

edge 35 to the front end edge 1a, the multi-layer portion of the side sheet 4 is

similarly folded and bonded, forming the stacked/fixed portion 37.

The front bond edge 35 and the rear bond edge 36 extend obliquely

with respect to both the longitudinal direction and the transverse direction. Between the front bond edge 35 and the rear bond edge 36, the multi-layer portion of the side sheet 4 previously folded in two forms the leakage

preventing wall 30 that can rise from the skin-side surface 2a, as shown in Fig. 4. It should be noted that the front end 30a of the leakage preventing wall 30 refers to one end of the front bond edge 35 that is closer to the front end edge 1a, and the rear end 30b of the leakage preventing wall 30 refers to one end of the rear bond edge 36 that is closer to the rear end edge 1 b. The length of the leakage preventing wall 30 refers to a dimension measured La from the front end 30a to the rear end 30b. The elastic members 32, 33 exert an elastic contractive force between the front end 30a and the rear end 30b, so that an elastic force acts to bring the front end 30a and the rear end 30b closer to each other, whereby the main body 2 is curved as shown in Fig. 1 and each side sheet 4 is raised from the skin-side surface 2a between the front end 30a and the rear end 30b, providing the leakage preventing wall 30.

Because the side sheet 4 at the stacked/fixed portion 37 is folded in a multi-layer structure and then bonded and fixed as shown in Fig. 5, the leakage preventing wall 30 includes: a lower inclined panel 30A extending obliquely upward from the rising base 31 toward the outside; an intermediate inclined panel 30B extending obliquely upward from the upper end of the lower inclined panel 30A toward the longitudinal centerline Oy-Oy; and a skin-contacting panel 30D extending obliquely upward from the upper end of the intermediate

inclined panel 30B toward the outside, as shown in the half sectional view of

Fig. 4. Referring to Fig. 3, the main body 2 of the sanitary napkin 1 will be described hereinbelow with respect to the shape. It should be noted that Fig. 3 is a top plan view showing the same sanitary napkin 1 as the top plan view of Fig. 2.

Along the transverse reference line Ox-Ox, the fold-back flaps 41 are disposed to project transversely outward from the main body 2. Each fold-back flap 41 extends over a given length with center at the transverse reference line Ox-Ox. Rearward of the fold-back flaps 41 are disposed rear flaps 42 also projecting transversely outward from the main body 2; forward of the fold-back flaps 41 are disposed front flaps 43 projecting transversely outward from the main body 2. Since the sanitary napkin 1 has bilateral symmetry about the longitudinal centerline Oy-Oy, the right and left flaps are of symmetrical shape.

As used herein, the term "half-width" refers to a dimension measured transversely from the longitudinal centerline Oy-Oy to one side edge of the sanitary napkin 1.

The half-width from the longitudinal centerline Oy-Oy to a side edge 41a of the fold-back flap 41 is largest on the transverse reference line Ox-Ox, wherein Wa designates the largest half-width. The side edge 41a is generally parallel to the longitudinal centerline Oy-Oy so as to provide an almost constant half-width over a given length of the side edge 41a. Between the fold-back flap 41 and the front flap 43 is provided a first narrowest portion of a smallest half-width Wb. At the first narrowest portion, the napkin's edge

provides a first starting point 44. The fold-back flap 41 has a front edge 41b

that is curved to gradually increase the half-width rearward from the first starting point 44 and continue to the side edge 41a. The front flap 43 has a side edge 43a that is curved to gradually

increase the half-width forward from the first starting point 44.

Between the fold-back flap 41 and the rear flap 42 is provided a second narrowest portion of a smallest half-width Wc. The fold-back flap 41 has a rear edge 41c that is curved to gradually increase the half-width forward from the second narrowest portion and continue to the side edge 41a.

At the second narrowest portion, the napkin's edge provides a second starting point 45 from which the half-width starts to increase rearward. The rear flap 42 extends from the second starting point 45 to the rear end edge 1b of the sanitary napkin 1.

The rear flap 42 may be divided in three areas: an intermediate portion 42A; a front spreading portion 42B; and a rear converging portion 42D.

In the intermediate portion 42A, the rear flap 42 has a linear side edge

42a extending over a length L2. As used herein, the term "linear side edge" should not be construed as limited to an edge extending in a perfect straight line, but may extend with a deviation within a range of +5 mm transversely from an imaginary straight line Lh that intersects with the edge of the rear flap at two points (the two intersections are spaced by L2). In the present embodiment, the side edge 42a of the intermediate portion 42A is slightly curved outward as shown in Figs. 2 and 3. Therefore, the imaginary straight line Lh is set so as not to be spaced more than 5 mm inwardly apart from the side edge 42a, wherein front and rear intersections between the imaginary straight line Lh and

the edge of the rear flap are referred to as front and rear boundary points 46,

47, respectively.

If the side edge 42a is a perfect straight line, front and rear ends of the linear side edge 42a may be the front and rear boundary points 46, 47, respectively.

The side edge 42a or the imaginary straight line Lh may be parallel to the longitudinal centerline Oy-Oy. In an alternative, the side edge 42a or the imaginary straight line Lh may be so inclined as to come closer to the longitudinal centerline Oy-Oy rearwardly.

The front spreading portion 42B extends from the second starting point 45 to the front boundary point 46. The front spreading portion 42B has an edge 42b that is curved to gradually increase the half-width rearward from the second starting point 45 to the front boundary point 46. Here, W1/L1 is preferably equal to or greater than 0.7, more preferably equal to or greater than 1 , where W1 represents a width from the second starting point 45 to the front boundary point 46 and L1 represents a length from the second starting point 45 to the front boundary point 46. The upper limit of W1/L1 is preferably about 2. With this construction, the edge 42b may be curved so that the front spreading portion 42B sharply spreads transversely.

Rearward of the rear boundary point 47, the rear flap 42 has the rear converging portion 42D. The rear converging portion 42D has an edge 42c that is curved to gradually decrease the half-width rearward from the rear boundary point 47 to the rear end edge 1 b.

In the present embodiment in which the side edge 42a extends linearly over the length L2, the rear flap 42 has an appropriate width although

extending over a large area.

Hereinbelow, preferred dimensions of the individual portions, as well

as dimensional relationships between the portions, will be described. Dimensions of the main body 2 are measured with the sanitary napkin 1 being developed flat as shown in Figs. 2 and 3.

The half-width Wb at the first starting point 44 located forward of the fold-back flap 41 is almost equal to the half-width Wc at the second starting point 45 located forward of the rear flap 42. The half-width from the longitudinal centerline Oy-Oy to side edge 42a of the rear flap 42 is larger than that to the side edge 41 a of the fold-back flap 41.

The main absorbent region 10 between the longitudinal compressed grooves 11, 11 has a width of 10 to 40 mm, and the side edges 6c, 6c of the liquid absorbent layer 6 are located outside the longitudinal compressed grooves 11, 11 and the first outside longitudinal compressed grooves 21 , 21.

A length L3 from the transverse reference line Ox-Ox to the second starting point 45 is in the range of 40 to 70 mm. With the length L3 being set within the range and W1/L1 being equal to or greater than 0.7, the edge 42b of the front spreading portion 42B may extend along the edge of the leg opening of the undergarment without projecting into the leg opening.

The length L2 of the linear side edge 42a of the intermediate portion

42A of the rear flap 42, i.e., the length from the front boundary point 46 to the rear boundary point 47 is at least 1/3 of the length from the second starting point 45 to the rear end edge 1b. The length L2 is preferably equal to or greater than 60 mm, more preferably equal to or greater than 100 mm. The upper limit of L2 is preferably (but not limited to) about 200 mm. The rear flaps 42, 42 extend over a large area longitudinally and transversely, improving

the effect of preventing transverse leakage of menstrual blood.

The length of the rear flap 42, i.e., the length from the second starting point 45 to the rear end edge 1b is preferably equal to or greater than 40%,

more preferably equal to or greater than 50% the length from the front end

edge 1a to the rear end edge 1b. The sanitary napkin 1 may be larger than

the conventional one in both length and width. The length is equal to or

greater than 400 mm, preferably equal to or greater than 410 mm and its upper

limit is (but not limited to) about 500 mm. On the other hand, the width (i.e., a

maximum distance between the side edges 42a, 42a of the rear flaps 42, 42) is equal to or greater than 180 mm and its upper limit is (but not limited to) about

300 mm. The main absorbent region 10 has a length capable of covering a region from the vaginal opening to the cleft of the buttocks and may be equal

to or greater than 120 mm.

The rear end 30b of the leakage preventing wall 30 is located farther rearward than the second starting point 45 and the front boundary point 46,

wherein the length from the second starting point 45 to the rear end 30b is equal to or greater than 30 mm, preferably equal to or greater than 50 mm.

On the other hand, the rear end 30b of the leakage preventing wall 30 is not spaced more than 20 mm apart longitudinally from the rear end 10a of the main

absorbent region 10. The length of the leakage preventing wall 30 from the

front end 30a to the rear end 30b is equal to or greater than 120 mm.

When the side sheet 4 forming the leakage preventing wall 30 is fully

developed transversely outward between the front end 30a and the rear end

30b, the side sheet 4 preferably has a maximum width of 20 to 50 mm from the

rising base 31 of the leakage preventing wall 30.

When thus fully developed between the front end 30a and the rear end 30b, the leakage preventing wall 30 projects transversely outward beyond the

first and second starting points 44, 45. At a distance Lg or more rearwardly

from the transverse reference line Ox-Ox, however, the edge 42b of the front

spreading portion 42B does not coincide with the edge of the fully developed

leakage preventing wall 30.

When the sanitary napkin 1 is worn, the leakage preventing wall 30

near the transverse reference line Ox-Ox is supposed to come into contact with the thigh. At the distance Lg or more rearwardly from the transverse reference line Ox-Ox, on the other hand, the leakage preventing wall 30 does

not come into contact with the thigh. In case of an average Asian adult woman, the distance Lg is 80+ 10 mm.

Even when the leakage preventing wall 30 not in contact with the thigh falls outward during wear, however, the edge 42b of the front spreading portion

42B is present outside the fallen leakage preventing wall 30, so that the undergarment can be prevented from being stained with body liquid on the

fallen leakage preventing wall 30.

In Fig. 3, a free end 30E of the leakage preventing wall 30 that is

developed transversely outward between the second starting point 45 and the

rear end 30b is shown with a dotted line, wherein the leakage preventing wall

30 is constrained at the second starting point 45 so as not to project

transversely beyond the starting point 45. As shown in Fig. 3, the front

spreading portion 42B of the rear flap 42 sharply spreads transversely, W1/L1

is equal to or greater than 0.7, and the half-width from the longitudinal

centerline Oy-Oy to the imaginary straight line Lh is significantly large.

Accordingly, the free end 30E of the leakage preventing wall 30 does not project transversely beyond the edge 42b of the front spreading portion 42B or

the linear side edge 42a of the intermediate portion 42A.

Between the second starting point 45 and the rear end 30b, as

mentioned above, the fallen leakage preventing wall 30 has a maximum width

We of 20 to 50 mm from the rising base 31. On the other hand, a width Wf

from the rising base 31 to imaginary straight line Lh is at least 5 mm, preferably

at least 10 mm larger than the width We. The width Wf is in the range of 25 to 60 mm.

On the garment-side surface of the sanitary napkin 1 , there are disposed pressure-sensitive adhesive layers, as shown in Fig. 2. The fold-back flap 41 has a front pressure-sensitive adhesive layer 51. The rear flap 42 has first and second rear pressure-sensitive adhesive layers 52, 53 that are separate from each other in the longitudinal direction. Furthermore,

central pressure-sensitive adhesive layers 54 are disposed on each side of the longitudinal centerline Oy-Oy. The central pressure-sensitive adhesive layers 54 are located inside the rising bases 31 of the leakage preventing walls 30

and extend longitudinally within the region of the liquid absorbent layer 6.

In the fold-back flap 41 , as shown in Figs. 4 and 5, a reinforcing sheet

56 is interposed between and bonded to the backsheet 5 and the side sheet 4.

Also in the rear flap 42, a reinforcing sheet 57 is interposed between and

bonded to the backsheet 5 and the side sheet 4.

Next, preferred examples of the individual components of the sanitary

napkin 1 will be described.

The topsheet 3 is a liquid-permeable sheet, such as a through-air

bonded nonwoven fabric, a spunlaced nonwoven fabric, or an apertured resin film (resin film formed with a large number of liquid passage holes). The

backsheet 5 is a resin film that is impermeable to liquid but may be breathable. The liquid absorbent layer 6 may be a layer of pulp, a layer of pulp and superabsorbent polymer, or an air-laid nonwoven fabric in which only pulp or pulp and rayon are deposited by air-laid process and the fibers are fixed together through an adhesive. The liquid permeable layer 7 is a bulky nonwoven fabric of a three-dimensional network structure, such as a through-air bonded nonwoven fabric or an air-laid nonwoven fabric in which pulp and synthetic fibers are deposited by air-laid process and the fibers are fixed together through an adhesive.

The side sheet 4 is impermeable to liquid and is preferably treated to be water-repellent. The side sheet 4 may be a meltblown nonwoven fabric, a spunbonded nonwoven fabric, or a laminated composite of spunbond/meltblown/spunbond. The reinforcing sheets 56, 57 may be of a spunbonded nonwoven fabric, a point-bonded nonwoven fabric, a meltblown nonwoven fabric, or a paper material. The pressure-sensitive adhesive layers 51 , 52, 53 and 54 may be of a rubber-based hot-melt type adhesive.

Hereinbelow, the function of the sanitary napkin 1 will be described. Fig. 1 shows a state where the sanitary napkin 1 is attached to an undergarment 60 such as a sanitary panty. The undergarment 60 has leg openings 61 , 61. Between a front body 62 and a rear body 63, the undergarment 60 has a crotch part 64 on which the front portion of the sanitary

napkin 1 is placed.

Through the central pressure-sensitive adhesive layers 54, the garment-side surface 2b of the main body 2 is adhered to the inner surface of

the undergarment 60 from the crotch part 64 to the lower part of the back body 63. The fold-back flaps 41 are folded back along the side edges of the crotch part 64 of the undergarment 60 and the front pressure-sensitive adhesive layers 51 on the fold-back flaps 41 are adhered to the outer surface of the crotch part 64. The rear flaps 42 kept in a developed state are adhered to the inner surface of the lower part of the back body 63 through the first rear pressure-sensitive adhesive layers 52 and the second rear pressure-sensitive adhesive layers 53. When the undergarment 60 is worn, the longitudinal central portion of the front main absorbent region 10A, i.e., the intersection of the longitudinal centerline Oy-Oy and the transverse reference line Ox-Ox and its surrounding area may come into contact with the woman's vaginal opening, the intermediate portion between the front main absorbent region 10A and the intermediate main absorbent region 10B may confront the perineum, and the intermediate main absorbent region 10B may confront the anus. Accordingly, the rear main absorbent region 10D may extend along the cleft of the buttocks and the rear auxiliary absorbent region 17 may confront the coccyx.

In the sanitary napkin 1 , the skin-side surface 2a tends to be recessed as shown in Fig. 1 due to the longitudinal elastic contractive force of the leakage preventing walls 30, whereby the leakage preventing walls 30 are

raised from the skin-side surface 2a.

Fig. 3 shows pressure surfaces 71, 71 on both sides of the sanitary

napkin 1. The pressure surfaces 71 , 71 represent surfaces from which a

compressive force (clamping force) is exerted on the sanitary napkin 1 when the sanitary napkin 1 is held between the wearer's thighs.

When the sanitary napkin 1 is subjected to a compressive force from

the pressure surfaces 71 , 71 , the compressive force may concentrate in the

front main absorbent region 10A and the intermediate main absorbent region

10B. Particularly in the front main absorbent region 10A, the liquid absorbent

layer 6 is transversely compressed. With such compression, the front main absorbent region 10A held between the longitudinal compressed grooves 11 ,

11 is raised toward the wearer's body, facilitating close contact with the vaginal opening and its surrounding region. In addition, since the undergarment exerts a tightening force on the intermediate main absorbent region 10B and the rear main absorbent region 10D along the longitudinal centerline Oy-Oy, the intermediate main absorbent region 10B and the rear main absorbent

region 10D can fit in the cleft of the buttocks when the wearer is in a standing position, minimizing the space between the sanitary napkin 1 and the wearer's body.

In Fig. 7, front and rear portions of the sanitary napkin 1 are indicated

by 1A and 1B, respectively, and the boundary therebetween is indicated by a

line Lx1-Lx1. When the wearer of the sanitary napkin 1 lies on her back

during sleep, the buttocks exert a pressure on the sanitary napkin 1 so that the

rear portion 1 B is compressed flat. Near the line Lx1-Lx1 , accordingly, the

rear portion 1 B tends to be bent from the front portion 1A, leaving a space

between the skin-side surface 2a of the main body 2 and the wearer's body.

In the sanitary napkin 1 , however, since the rear flaps 42 project

transversely outward from the second starting points 45 coinciding with the line

Lx1-Lx1 so that the edges 42b of the front spreading portions 42B extend along the edges of the leg openings 61 of the undergarment 60, menstrual

blood flowing obliquely rearward beyond the leakage preventing wall 30 as

indicated by an arrow 62 can be effectively prevented from leaking out.

Here, the leakage preventing walls 30, 30 in contact with the thighs

hardly fall outward, and therefore, can easily be kept in a position rising from

the skin-side surface 2a. However, the leakage preventing walls 30, 30 do

not come into contact with the thighs at the distance Lg or more, easily causing outward fall of the leakage preventing walls 30, 30. Particularly when the

wearer lies on her back during sleep, the leakage preventing walls 30, 30 tend to fall flat due to the pressure exerted on the rear portion 1 B from the buttocks.

However, even when the leakage preventing wall 30 is fully developed transversely outward, the leakage preventing wall 30 does not project beyond the edge 42b of the front spreading portion 42B at the distance Lg or more.

Furthermore, even when the leakage preventing wall 30 is developed

transversely outward at a position between the second starting point 45 and the rear end 30b, the free end 30E does not project beyond the edge of the

rear flap 42. Accordingly, menstrual blood on the leakage preventing wall 30 hardly comes into contact with the undergarment 60.

The leakage preventing wall may be of any rising position. For

instance, Fig. 6 shows a leakage preventing wall 30L with a rising base 31 A

over the liquid absorbent layer 6. At an upper end of a rising wall panel 30J,

a skin-contacting panel 30K projects both toward and away from the

longitudinal centerline Oy-Oy.

Although the present invention has been illustrated and described with

respect to exemplary embodiments thereof, it should be understood by those skilled in the art that the foregoing and various other changes, omission and

additions may be made therein and thereto, without departing from the spirit

and scope of the present invention. Therefore, the present invention should

not be understood as limited to the specific embodiments set out above but to

include all possible embodiments which can be embodied within a scope

encompassed and equivalent thereof with respect to the features set out in the

appended claims.

INDUSTRIAL APPLICABILITY According to the present invention, as has been described hereinabove, an undergarment can be effectively prevented from being stained

with menstrual blood flowing obliquely rearward during sleep.

Claims

1. A sanitary napkin comprising: an elongated main body (2) having a skin-side surface (2a) and a garment-side surface (2b) and including a liquid absorbent layer (6); a pair of leakage preventing walls (30) disposed on the skin-side surface (2a) of the main body (2) and extending longitudinally of the main body (2) in parallel with each other; and a pressure-sensitive adhesive layer (54) disposed on the garment-side surface (2b) of the main body (2) for adhering to an inner surface of an undergarment, the main body (2) having a rear portion with rear flaps (42) projecting from transversely opposing sides thereof, each rear flap (42) having a starting point (45) from which a width of the sanitary napkin starts to increase and a spreading portion (42B) in which the width gradually increases rearward from the starting point (45), each leakage preventing wall (30) being composed of: a sheet (4) that is fixed to the skin-side surface (2a) of the main body (2) to have a longitudinally extending rising base (31); and an elastic member that is so tensioned between longitudinal front and rear ends (30a, 30b) of the leakage preventing wall (30) as to raise the sheet (4) from the skin-side surface (2a), the rear end (30b) of the leakage preventing wall (30) being located rearward of the starting point (45) of the rear flap (42), wherein when developed transversely outward at a position between the

starting point (45) and the rear end (30b), the sheet (4) of the leakage

preventing wall (30) rearward of the starting point (45) extends exclusively inside an edge of the rear flap (42).

2. A sanitary napkin according to claim 1 , wherein when developed

transversely outward at a position spaced 80+ 10 mm apart rearwardly from a

transverse reference line (Ox-Ox) on which the sanitary napkin is intended to

face a center of the vaginal opening, the sheet (4) of the leakage preventing wall (30) extends exclusively inside the edge of the rear flap (42).

3. A sanitary napkin according to claim 1 , wherein rearward of the spreading portion (42B), the rear flap (42) has an intermediate portion (42A)

with a linear side edge (42a) extending longitudinally over a length equal to or greater than 60 mm.

4. A sanitary napkin according to claim 3, wherein the linear side edge (42a) is parallel with a longitudinal centerline (Oy-Oy) of the sanitary napkin.

5. A sanitary napkin according to claim 3, wherein the linear side edge (42a) is so inclined as to come closer to a longitudinal centerline (Oy-Oy) of

the sanitary napkin rearwardly.

6. A sanitary napkin according to claim 3, wherein W1/L1 is equal to or

greater than 0.7, where L1 represents a length from the starting point (45) to a

front end (46) of the linear side edge (42a) and W1 represents a width from the

starting point (45) to the front end (46) of the linear side edge (42a).

7. A sanitary napkin according to claim 1 , wherein the skin-side surface (2a) of the main body (2) has an elongated main absorbent region (10) that is surrounded by a compressed groove and intended to face the wearer's body

from the vaginal opening to the cleft of the buttocks, wherein the main absorbent region (10) has a rear end (10a) that is not spaced more than 20 mm apart longitudinally from the rear end (30b) of the leakage

preventing wall (30).

8. A sanitary napkin according to claim 1 , wherein when fully developed transversely outward, the sheet (4) of the leakage preventing wall (30) has a maximum width of 20 to 50 mm from the rising base (31).

9. A sanitary napkin according to claim 1 , which has a length equal to or greater than 400 mm and a width equal to or greater than 180 mm between the linear side edges (42a) of the rear flaps (42).