Disposable diaper

[0002] This invention relates to a disposable diaper for absorbing and containing body wastes.

[0003] It is well known to use an elastically non-stretchable nonwoven fabric or a plastic film as stock materials for top- and backsheets of a disposable diaper and to provide the diaper along peripheral edges of the waist-opening and the leg-openings with elastic members secured under an appropriate tension to the diaper so that gathers may be formed along these peripheral edges as the elastic members contract and thereby ensure a good fit of the diaper around the waist and the legs of the wearer.

[0004] The diaper of prior art is normally in its shrinked state under contraction of the elastic members and immediately before the diaper is put on the wearer, much time and trouble are required to stretch the gathers so that the waist-opening as well as the leg-openings may be sufficiently widened to facilitate putting the diaper on the wearer. The diaper of prior art is inconvenient also in that when the diaper put on the wearer it is not necessarily able to follow complex movements and therefore is apt to slip down or to become twisted. This is because the diaper is stretchable only in the direction along which the elastic members extend.

[0005] It is an object of this invention to provide a disposable diaper designed so that time and trouble otherwise taken to stretch the gathers in order to put the diaper on the wearer may be eliminated and the diaper may follow movement of the wearer as closely as possible.

[0006] According to this invention, there is provided a disposable diaper comprising a topsheet intended to come in contact with the wearer's skin, a backsheet intended to come in contact with the wearer's garment and an absorbent core disposed between the topsheet and the backsheet wherein, the diaper has a front waist region, a rear waist region and a crotch region extending between the waist regions so that transversely opposite side edges of the crotch region surround the wearer's legs, wherein:

[0007] the topsheet and the backsheet in the front and rear waist regions are elastically stretchable in a transverse direction of the diaper while the topsheet and the backsheet at the transversely opposite side edges of the crotch region are elastically stretchable in a longitudinal direction of the diaper and in the transverse direction and the topsheet and the backsheet in the remaining regions are elastically stretchable at least in the transverse direction.

[0008] The disposable diaper according to the invention has no gathers and facilitates the diaper to be put on the wearer. The diaper according to this invention does not obstruct a movement of the wearer's legs and crotch region because the regions around the legs as well as the crotch region of the diaper are elastically stretchable longitudinally and transversely of the diaper.

[0009] FIG. 1 is a partially cutaway plan view showing a disposable diaper according to one embodiment of this invention;

[0010] FIG. 2 is a sectional view taken along line II—II in FIG. 1;

[0011] FIG. 3 is a view similar to FIG. 2 but showing another embodiment of this invention;

[0012] FIG. 4 is a view similar to FIG. 1 but showing still another embodiment of this invention; and

[0013] FIG. 5 is a sectional view taken along line V—V in FIG. 4.

[0014] Details of a disposable diaper according to this invention will be more fully understood from the description given hereunder with reference to the accompanying drawings.

[0015] FIG. 1 is a partially cutaway plan view showing a disposable diaper 1 and FIG. 2 is a sectional view taken along line II—II in FIG. 1. The diaper 1 comprises a liquid-previous topsheet 2 intended to come in contact with the wearer's skin, a liquid-impervious backsheet 3 intended to come in contact with the wearer's garment and a liquid-absorbent core 4 disposed between these two sheets 2, 3. Longitudinally, the diaper 1 has a front waist region 6, a rear waist region 7 and a crotch region 8 extending between these two waist regions 6, 7. The crotch region 8 has its transversely opposite side edges 9, 9 partially cut away to form curved edges 10, 10 adapted to fit around the wearer's legs. The rear waist region 7 is provided on its transversely opposite side edges with tape fasteners 11, 11, respectively. The top- and backsheets 2, 3 are placed upon and joined to each other by means of hot melt adhesive 12 along their portions extending outward beyond a peripheral edge of the core 4.

[0016] In such diaper 1, both the top- and backsheets 2, 3 are elastically stretchable in the transverse direction which is orthogonal to the longitudinal direction of the diaper 1. It should be understood here that, in the vicinity of the side edges 9, 9 of the crotch region 8, the top- and backsheets 2, 3 are partially cut away and these portions of the sheets 2, 3 thus cut away are replaced by separate top- and backsheets 22, 23 both associated with the leg openings. These top- and backsheets 22, 23 are elastically stretchable longitudinally as well as transversely of the diaper 1. The topsheet 22 associated with the leg-openings is preferably sweat-absorbent and breathable while said backsheet 23 associated with the leg-openings is preferably breathable and liquid-impervious. These top- and backsheets 22, 23 are bonded to the respective inner surface of the top- and backsheet 2, 3, for example, by means of hot melt adhesive 12 applied thereon in a pattern of sine curves. The top- and backsheets 22, 23 associated with the leg-openings are also placed upon and joined to each other by means of hot melt adhesive 13 applied thereon in a pattern of sine curves or small dots (see FIG. 1).

[0017] The diaper 1 can be put on the wearer merely by unfolding it as seen in FIG. 1. This diaper 1 is free from the gathers as in the conventional diaper and therefore can be put on the wearer immediately after the diaper 1 has been unfolded without time and trouble taken to stretch the gathers. The top- and backsheets 2, 3 may be circumferentially stretched to put the diaper 1 on the wearer with a good fit. The diaper 1 put on the wearer does not obstruct a movement of baby's legs because the portion of diaper 1 extending around the wearer's legs is free to be stretched in all directions.

[0018] FIG. 3 is a view similar to FIG. 2 but showing another embodiment of this invention. According to this embodiment of diaper 1, the crotch region 8 is provided along each of its side edges 9 with a single sheet 25 associated with the leg-opening bonded to the respective inner surfaces of the top- and backsheets 2, 3 by means of hot melt adhesive 12, 13. This single sheet 25 associated with the leg-opening serves both as the top- and backsheets 22, 23 associated with the leg-openings in the embodiment shown in FIG. 2.

[0019] FIGS. 4 and 5 are respectively a view similar to FIG. 1 but showing still another embodiment of this invention and a sectional view taken along line V—V in FIG. 4. According to this embodiment of diaper 1, the topsheet 2 is divided into topsheet sections 2A, 2B for the front and rear waist regions and a topsheet section 2C for the crotch region. Similarly, the backsheet 3 is divided into backsheet sections 3A, 3B and a backsheet section 3C for the crotch region. The topsheet sections 2A, 2B for the front and rear waist regions as well as the backsheet sections 3A, 3B for the front and rear waist regions are elastically stretchable transversely of the diaper 1. The topsheet sections 2C, 3C for the crotch region are elastically stretchable longitudinally as well as transversely of the diaper 1. These sheet sections 2A—2C and 3A-3C are bonded one to another along their overlapping zones by means of hot melt adhesive 12, 13 applied thereto in a pattern of sine curves or small dots. Referring to FIG. 5, the core 4 may be appropriately joined to the respective inner surfaces of the top- and backsheet sections 2A-2C and 3A—3C in the front and rear waist regions 6, 7 and in the crotch region 8. Similarly to the diaper 1 of FIG. 1, the diaper 1 according to this embodiment also can be easily put on the wearer and the diaper 1 having been put on the wearer does not obstruct a movement of the wearer legs as well as the wearer's crotch.

[0020] To make the diaper 1 according to this invention, a nonwoven fabric or an elastomer film having a monoaxial stretchability can be used as stock material for the top- and backsheets or their sections 2, 2A, 2B, 3, 3A, 3B. Such nonwoven fabric or elastomer may be formed with a plurality of pores each having an appropriate size to obtain a desired liquid-previous property. A nonwoven fabric or an elastomer having a biaxial stretchability can be used as stock material for the top- and backsheet sections 22, 23 associated with the leg-openings, the single sheet 25 associated with each of the leg-openings and the top- and backsheet sections 2C, 3C of the crotch region. Bonding of such nonwoven fabric and film may be carried out using suitable adhesive agents such as hot melt adhesive or ultrasonic- or heat-sealing technique. It is important to perform operation of sheet-to-sheet bonding without deteriorating the original stretchability of these sheets. When adhesive agent is used, these sheets may be applied with adhesive agent in a pattern of sine curves to avoid an apprehensive deterioration of the sheets' original stetchability and at the same time to prevent the body fluids from flowing between the top- and bakcsheets 2, 3 from the core 4 toward the peripheral edge of the diaper 1.