WO2001056526A1

WO2001056526A1 - Improved crimp seal for absorbent articles

Info

Publication number: WO2001056526A1
Application number: PCT/US2001/003189
Authority: WO
Inventors: Stephanie A. Rutter; Ronald R. Mcfall; Steven R. Gilbert
Original assignee: The Procter & Gamble Company
Priority date: 2000-02-04
Filing date: 2001-01-31
Publication date: 2001-08-09
Also published as: AU2001233188A1

Abstract

Absorbent articles having an improved crimp seal are disclosed. The absorbent articles comprise a liquid pervious topsheet, an liquid impervious backsheet, and an absorbent core positioned between the topsheet and backsheet. The topsheet and backsheet are joined to each at a plurality of discrete spaced apart bonding sites. The bonding sites have a plan view which is in the shape of a simple closed figure with rounded sides. The bond sites may be arranged in rows where each row is offset with respect to the adjacent row of bonds. The disclosed crimp seal is particularly effective when used with a thermoplastic formed film topsheet. A sanitary napkin provided with the improved crimp seal is also disclosed. Such a sanitary napkin with integrity bonding on the topsheet of the napkin particularly demonstrates the advantages of the improved crimp seal.

Description

IMPROVED CRIMP SEAL FOR ABSORBENT ARTICLES

FIELD OF THE INVENTION

This invention relates to absorbent articles such as sanitary napkins, panty liners, diapers, and adult incontinence pads having an improved crimp seal for prevention of tearing and improper seal formation.

BACKGROUND OF THE INVENTION

Disposable absorbent articles are commercially available in a wide variety of configurations for the specific purpose of absorbing and retaining discharged body fluids. For example, disposable diapers and incontinent briefs are intended to absorb and contain urine and feces, bandages are intended to absorb and contain blood and other body exudates while catamenial pads (for example, sanitary napkins, pantiliners, and interlabial devices) are intended to absorb and retain menstrual fluids and other vaginal discharges. Regardless of the specific application, each absorbent article is intended to isolate the discharged fluids for preventing the undergarments, clothing, bedding etc. surrounding the disposable article from becoming soiled.

It is common for the topsheet layer to be affixed to the backsheet in a manner defining a continuous and relatively thin border segment which surrounds the perimeter of the thicker absorbent core. While the border segment may be continuous, disposable absorbent articles in which such a border segment is not continuous (for example, a border found only at the ends of the article) are also known. One effective manner of joining the topsheet layer to the backsheet layer is through the use of a crimp seal in which the application of heat and pressure causes the topsheet to be bonded to the backsheet layer. A typical crimp seal may be formed at a plurality of discrete bonding sites. For example, some currently marketed sanitary napkin disposable absorbent articles have a crimp seal which comprises a plurality of discrete bond sites which are square in shape and which are aligned in rows with respect to one another. While previously known crimp seals such as those described above function reasonably well for their intended purpose, they do demonstrate some drawbacks. For example, the use of a square shaped or similarly shaped bond site pattern for the formation of a crimp seal may create localized points of stress at the corners of such sites. Additionally, if the bond sites are aligned in rows, the layers of the topsheet and backsheet may "zipper" apart from one another if a tear in an individual bond site (created, for example, at a corner at a location of high stress) propagates along a row of bond sites. These drawbacks are particularly pronounced when the topsheet of the absorbent article is constructed from an apertured formed thermoplastic film or similar material.

These and other manufacturing challenges have resulted in a continued search for a manner of providing a crimp seal in a disposable absorbent article which will be both practical to manufacture and which will demonstrate superior performance.

SUMMARY OF THE PRESENT INVENTION

The present invention is directed to disposable absorbent articles such as sanitary napkins, panty liners, interlabial devices, tampons, diapers, and adult incontinence pads having an improved crimp seal. In one embodiment, the disposable absorbent article of the present invention has a pair of longitudinal side edges and a pair of end edges which form the periphery of the article. The absorbent article further has a length in a longitudinal direction and a width in a transverse direction. The absorbent article of this embodiment also comprises an absorbent core which has a body facing surface, a garment facing surface and an outer boundary. The article also comprises a substantially liquid impervious backsheet overlaying the garment facing surface of the absorbent core. The backsheet extends beyond at least a portion of the outer boundary of the core. The article also comprises a thermoplastic formed film liquid pervious topsheet. The tospsheet overlays the body facing surface of the absorbent core and extends beyond at least a portion of the core's outer boundary. The backsheet is at least partially peripherally joined to the topsheet. The article also comprises a plurality of discrete bonding sites for joining the topsheet to the backsheet. Each of the discrete bonding sites has the plan view shape of a simple closed figure with rounded sides. Additionally, each of the plurality of discrete bonding sites is offset with respect to the next adjacent bond site in at least one of the longitudinal direction or the transverse direction. In one preferred embodiment, each of the discrete bond sites may comprise a circular shape. Similarly, in another preferred embodiment, each of the discrete bond sites comprises an oval shape. In one preferred embodiment, the liquid impervious backsheet comprises a thermoplastic film of material.

Another embodiment of the present invention comprises a sanitary napkin having a pair of longitudinal side edges and a pair of end edges forming. These edges form the periphery of the sanitary napkin. The sanitary napkin further has a length in a longitudinal direction and a width in a transverse direction. The sanitary napkin includes an absorbent core having a body facing surface, a garment facing surface and an outer boundary. The sanitary napkin also includes a substantially liquid impervious backsheet overlaying the garment facing surface of the absorbent core. The backsheet extends beyond at least a portion of the outer boundary of the core. The sanitary napkin also includes a liquid pervious topsheet overlaying the body facing surface of the absorbent core and extending beyond at least a portion of the outer boundary of the core. The backsheet it at least partially peripherally joined to the topsheet. Additionally, in this embodiment, the sanitary napkin also includes a plurality of discrete bonding sites for joining the topsheet to the backsheet. Each of the discrete bonding sites has the plan view shape of a simple closed figure with rounded sides. Each of the plurality of discrete bonding sites is offset with respect to the next adjacent bond site in at least one of the longitudinal direction or the transverse direction.

Preferably, the plurality of discrete bonding sites may occupy a bond area having a width not greater than 10 mm. Preferably, the plurality of discrete bonding sites have a maximum distance from one such discrete bonding site to the next adjacent bonding site of not greater than 0.1 inches.

Preferably, the liquid pervious topsheet of the sanitary napkin comprises a thermoplastic formed film material. Preferably, the liquid impervious backsheet may comprise a thermoplastic film. In preferred sanitary napkins made according to the present invention, the topsheet and said backsheet are joined together solely through the application of discrete bonding sites without the need for a supplemental adhesive. The bonding sites may preferably have a bond density in the range of from about 175 to about 300 bonds per square inch. Preferably, the bonding area has a substantially uniform bond site density over the entire bonding area. Preferably, the topsheet is peripherally joined to the backsheet around the entire periphery of the sanitary napkin. BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter which is regarded as forming the present invention, it is believed that the invention will be better understood from the following description which is taken in conjunction with the accompanying drawings in which:

FIG. 1 is a top plan view of a preferred sanitary napkin embodiment of the present invention.

FIG. 2 is a lateral cross-sectional view taking along line 2—2 of FIG. 1.

FIG. 3 is an expanded view of a portion of FIG. 1 showing a preferred embodiment of discrete bonding sites according to the present invention.

FIG. 4 is a top plan view of an additional preferred sanitary napkin embodiment of the present invention. The sanitary napkin of this embodiment has a continuous peripheral crimp seal according to the present invention.

FIG. 5 is an expanded view of a portion of FIG. 4 showing an additional preferred embodiment of discrete bonding sites according the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to absorbent articles such as sanitary napkins, panty liners, interlabial devices, and adult incontinence pads which have an improved crimp seal formed therein.

A preferred embodiment of a sanitary napkin 20 of the present invention is shown in FIG. 1. As shown in FIG. 1, the sanitary napkin 20 preferably comprises an absorbent means (or "main body portion") 22, and two optional flaps 24. The sanitary napkin 20 has two surfaces, a body-facing surface or "body surface" 20A and a garment surface 20B. The sanitary napkin 20 is shown in FIG. 1 as viewed from its body surface 20A. The body surface 20A is intended to be worn adjacent to the wearer's body. The garment surface 20B is intended to be placed adjacent to the wearer's undergarments when the sanitary napkin 20 is worn.

The sanitary napkin 20 has two centerlines, a principal longitudinal centerline L and a principal transverse centerline T. The term "longitudinal", as used herein, refers to a line, axis or direction in the plane of the sanitary napkin 20 that is generally aligned with (e.g., approximately parallel to) a vertical plane which bisects a standing wearer into left and right body halves when the sanitary napkin 20 is worn. The terms "transverse" or "lateral" used herein, are interchangeable, and refer to a line, axis or direction which lies within the plane of the sanitary napkin 20 that is generally perpendicular to the longitudinal direction.

FIG. 1 shows that the main body portion 22 of the sanitary napkin 20 comprises the portion of the sanitary napkin without the flaps 24. The main body portion 22 has two spaced apart longitudinally oriented or side edges 26, two spaced apart transversely oriented end edges (or "ends") 28, which together form the periphery 30 of the main body portion. The main body portion 22 also has two end regions, which are designated first end region 32 and second end region 34. A central region 36 is disposed between the end regions 32 and 34. The end regions 32 and 34 extend outwardly in the longitudinal direction from the edges of the central region 36 about 1/8 to about 1/3 of the length of the main body portion. A detailed description of the characteristics of a central region and two end regions for a sanitary napkin is contained in U.S. Patent 4,690,680 issued to Higgins on September 1, 1987. The sanitary napkin 20 has a longitudinal central region 16 disposed along the length of at least a portion of the principal longitudinal centerline L, and longitudinal side regions 18 transversely outboard of the longitudinal central region 16.

The main body portion 22 of the sanitary napkin 20 can be of any thickness, including relatively thick, intermediate thickness, relatively thin, or even very thin (or "ultra thin"). An "ultra-thin" sanitary napkin 20 as described in U.S. Patents 4,950,264 and 5,009,653 issued to Osborn preferably has a caliper of less than about 3 millimeters. The embodiment of the sanitary napkin 20 shown in FIGS. 1-2 of the drawings is intended to be an example of an ultra-thin sanitary napkin. The main body portion 22 of the sanitary napkin 20 may also be relatively flexible, so that it is comfortable for the wearer. It should, however, be understood that the sanitary napkins shown are merely two examples of embodiments, and that the present invention is not limited to absorbent articles of the type or having the specific configurations shown in the drawings.

FIG. 2 shows the individual components of the main body portion 22 of the sanitary napkin 20 of the present invention. The main body portion 22 of the sanitary napkin preferably comprises at three primary components. These include a liquid pervious topsheet 38, a liquid impervious backsheet 40, and an absorbent core 42 positioned between the topsheet 38 and the backsheet 40. Other optional components, such as acquisition component 44 may also be included. The acquisition component 44 may either be a separate component positioned between the topsheet 38 and the absorbent core 42, or it may comprise part of a composite topsheet or part of the absorbent core 42.

The topsheet 38 is a liquid pervious component that permits liquids (e.g., menses and/or urine) to readily penetrate through its thickness. The topsheet 38 is preferably as compliant, soft feeling, and non-irritating to the wearer's skin as possible. A suitable topsheet 38 may be manufactured from a wide range of materials such as woven and nonwoven materials; polymeric materials such as apertured formed thermoplastic films, apertured plastic films, and hydroformed thermoplastic films; porous foams; reticulated foams; reticulated thermoplastic films; and thermoplastic scrims. Suitable woven and nonwoven materials can be comprised at least partially of natural fibers (e.g., wood or cotton fibers), synthetic fibers (e.g., polymeric fibers such as polyester, polypropylene, or polyethylene fibers) or from a combination of natural and synthetic fibers.

A preferred type of topsheet comprises an apertured formed film. Apertured formed films are preferred for the topsheet because they are pervious to body exudates and, if properly apertured, have a reduced tendency to allow liquids to pass back through and rewet the wearer's skin. Thus, the surface of the formed film which is in contact with the body remains dry, thereby reducing body soiling and creating a more comfortable feel for the wearer. Additionally, the benefits of the improved crimp seal of the present invention are more pronounced when the tophsheet material is a thermoplastic formed film or similar material. Therefore, the present invention allows the high strike-through and low re-wet fluid handling benefits of a formed film described above to be realized while reducing or eliminating topsheet tearing or improper seal formation issues which may otherwise arise from the use of such materials.

Suitable formed films are described in U.S. Patent 3,929,135, entitled "Absorptive Structures Having Tapered Capillaries", which issued to Thompson on December 30, 1975; U.S. Patent 4,324,246 entitled "Disposable Absorbent Article Having A Stain Resistant Topsheet", which issued to Mullane, et al. on April 13, 1982; U.S. Patent 4,342,314 entitled "Resilient Plastic Web Exhibiting Fiber-Like Properties", which issued to Radel, et al. on August 3, 1982; U.S. Patent 4,463,045 entitled "Macroscopically Expanded Three-Dimensional Plastic Web Exhibiting Non-Glossy Visible Surface and Cloth-Like Tactile Impression", which issued to Ahr et al. on July 31, 1984; U.S. Patent 4,637,819 entitled "Macroscopically Expanded Three-Dimensional Polymeric Web for Transmitting Both Dynamically Deposited and Statically Contacted Fluids From One Surface to the Other", which issued to Ouellette, et al. on January 20, 1987; U.S. Patent 4,780,352 entitled "Covering Structure For Absorbent Hygienic Sanitary Products, and an Absorbent Product Having Such A Covering", which issued to Palumbo on October 25, 1988; U.S. Patent 5,006,394 "Multilayer Polymeric Film" issued to Baird on April 9, 1991; and U.S. Patent Application Serial No. 08/442,935 entitled "Fluid Transport Webs Exhibiting Surface Energy Gradients" filed in the name of Ouellette, et al. on May 31, 1995 (PCT Publication WO 96/00548, published January 11, 1996).

The terms "apertures" and "apertured" may include holes and/or slits which create passageways though the film layer from one surface to the other. The apertures can all be of the same size and shape, or they may be of different sizes and shapes. The apertures may be localized or they may extend across the entire surface of the film 38. When the aperturing is localized, it may be in the form of a longitudinal central portion or strip which separates two longitudinal side portions of the film which are not apertured. In addition, the entire topsheet can be made from a film or the longitudinal central portion can be made from a film and the longitudinal side portions can be made from another material such as a fibrous nonwoven web.

The apertured film 38 can be made of a number of suitable materials. Suitable polymers from which to form the apertured film 38 include any material which can be formed into a film including, but not limited to, polyolefins and polyacrylates, as well as copolymers and blends thereof. Specific polymers include, but are not limited to, polyethylene (PE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE) and ethylene vinyl acetate (EVA). Combinations of these materials such as LDPE and LLDPE used (especially when used in the three-dimensional apertured formed films referenced above) are particularly effective. Typically the apertured film 38 will have a thickness between about 0.025 and about 1.0 millimeters and a percent open area due to the aperturing of between about 10 and about 40% based upon the surface area of the apertured film 38. Percent open area is calculated by specifying a unit area, calculating the surface area of all open areas within the specified unit area, dividing this total open area by the total surface within the specific unit area and then multiplying the quotient by 100 to yield percent open area. The size and number of apertures can be varied depending upon the viscosity and other properties of the body fluid being transported through the apertured film 38.

In preferred embodiments of the present invention, the body surface of the topsheet 38 is hydrophilic so that liquids will be transferred through the topsheet more readily. This diminishes the likelihood that menstrual fluid will flow off the topsheet rather than flowing into and being absorbed by the absorbent core. The body surface of the topsheet 38 can be made hydrophilic by treating it with a surfactant. Suitable methods of treating a topsheet with a surfactant are described in U.S. Patent 4,950,254 issued to Osborn.

In a preferred embodiment, the topsheet 38 comprises an apertured formed film made in accordance with U.S. Patents 4,342,314 issued to Radel, et al. and 4,463,045 issued to Ahr, et al., which is marketed on sanitary napkins as the DRI- WEAVE topsheet by The Procter & Gamble Company of Cincinnati, OH. Such an apertured film is preferably obtained as product No. X-5652 from Tredegar Film Products of Terre Haute, IN. In this preferred embodiment, during manufacture the resin used to form the apertured film is preferably provided with a surfactant incorporated therein.

If used, the acquisition component (or "acquisition layer") 44 preferably lies beneath the topsheet 38. The terms "layer" or "web", as used herein, include but are not limited to single unfolded sheets, folded sheets, strips of material, loose or bonded fibers, multiple layers or laminates of material, or other combinations of such materials. These two terms are thus, not limited to single unfolded layers or sheets of material. The acquisition component 44 may provide void volume beneath the topsheet 38 to increase the ability of the sanitary napkin to draw liquids through the topsheet 38. In the preferred embodiment described herein, the acquisition component 44 preferably provides resiliency to lateral compressive forces so that the sanitary napkin 20 has improved resistance to bunching. The acquisition component 44 may have an effective average pore size that is equal to that of the topsheet 38, or less than that of the topsheet. The acquisition component 44 should be liquid permeable. The acquisition component 44 is also preferably compliant, soft feeling, and non-irritating to the user's skin. The acquisition component 44 has a body-facing face (or side), and a garment- facing face. The acquisition component 44 may be of any suitable size and shape. In the embodiment shown in FIG. 1, the acquisition component 44 is in the shape of a race track with slightly concave side edges, as is the portion of the topsheet 38 that overlies the main body portion 22 of the sanitary napkin 20. The dimensions of the acquisition component 44, however, are preferably not as large as those of the topsheet 38. In other embodiments, the acquisition component may be in the form of a piece of material that is smaller than the absorbent core 42.

Preferably, acquisition components 44 are be made from materials suitable for the above purposes that are capable of having the topsheet 38 fused to them. The acquisition component 44 may, for example, be comprised of woven or nonwoven materials. The fibers or other components of these materials may be synthetic, or partially synthetic and partially natural. Suitable synthetic fibers include polyester, polypropylene, polyethylene, nylon, viscose rayon, or cellulose acetate fibers. Suitable natural fibers include cotton, cellulose, or other natural fibers. The acquisition component 44 may also be at least partially comprised of cross-linked cellulose fibers. The acquisition component 44, if nonwoven, can be made by a number of different processes. These include, but are not limited to: air laid, wet laid, meltblown, spunbonded, carded, thermally bonded, air-through bonded, powder bonded, latex bonded, solvent bonded, spunlaced, and combinations of the foregoing.

Suitable thermally bonded wet laid nonwoven webs (which may be referred to as "TBOWL" for brevity) are described in U.S. Patent 5,549,589 entitled "Fluid Distribution Member for Absorbent Articles Exhibiting High Suction and High Capacity" issued to Horney, et al. on August 27, 1996.

In the embodiment shown in the drawings, the acquisition component 44 preferably comprises a laminate of two materials. The uppermost portion of this laminate preferably comprises an 19 g/yd^ (22.5 g/m^) spunbonded polypropylene nonwoven material referred to as product No. 065MLPV60U (or "P-9") obtained from Fiberweb, North America of Washougal, WA. The uppermost portion preferably has a void volume of about 11.2 cc/g measured at 689 dynes per square centimeter (0.01 psi.), and an average pore size, measured using the Laplace/Washburn equation for capillary tension of between about 60 and about 70 microns.

The underlying portion of the laminate preferably comprises a multi-bonded air laid material that is thermally bonded using powder bonding and latex bonding. In a preferred embodiment, this multi-bonded air laid material comprises about 77% cellulose fibers, about 20% powder binder, and about 3% latex coating (1.5% sprayed on each side of the web) and has a basis weight of about 50 g/yd^ (about 60 g/m^). (Unless otherwise stated, all percentages herein are by weight.) Such a multi-bonded air laid material is preferably obtained as product No. 90830X312 from Merfin Hygienic Products, Ltd. of Delta, British Columbia, Canada.

The laminate is preferably manufactured by depositing the multi-bonded air laid material on the spunbonded polypropylene nonwoven material. The spunbonded material is used as a process aid or carrier web in the process of forming this laminate. The laminate preferably has a caliper of about 1.2 mm measured at a pressure of 68.9 Pascals, and a void volume of about 13.6 cc/g measured at 689 dynes per square centimeter. The acquisition component 44 is preferably hydrophilic. The acquisition component 44 may be more hydrophilic than the absorbent core, or it can have the same hydrophilicity as the absorbent core. If desired, the acquisition component 44 can be treated with a surface active agent to provide make it more hydrophilic. Preferably, it has the same hydrophilicity as the absorbent core.

In alternative embodiments, the spunbonded polypropylene nonwoven material may have a greater or a lower basis weight, or it may be replaced by an air laid tissue, a wet laid tissue, or any of the materials described above. If a wet laid tissue is used instead of a polypropylene nonwoven material, the orientation of the laminate is preferably reversed so that in the finished product, the multi-bonded air laid nonwoven material lies above the wet laid tissue layer. In the case of thicker sanitary napkins, any of the acquisition components described above can be used. Additionally, in one preferred thicker sanitary napkin embodiment, a low density latex bonded air laid material can be used as the entire acquisition component (that is, no lamination is required). A low density latex bonded air laid material suitable for this purpose is a material having a basis weight of about 80 g/m^ known as product No. FG413MHB, which is obtained from Walkisoft, USA of Mt. Holly, NC. The topsheet 38 may optionally be fused to one or more other underlying components. This fusion or bonding may be present in addition to the discrete spaced upon bond sites of the crimp seal of the present invention described below. For simplicity, the optional bonding of the topsheet to one or more other components will be described as "integrity bonding." The bonding of the topsheet to the backsheet to form the crimp seal of the present invention will generally be referred to as "crimp bonding." As noted, the use of integrity bonding of the topsheet is preferred, but optional. It should be noted, however, that the use of such integrity bonding may result in higher levels of stress on the topsheet 38, thereby resulting in more pronounced benefit of the improved crimp bonding of the present invention.

The integrity bonding of the topsheet 38 is generally described herein as being between the topsheet 38 and the acquisition component 44. This has been done for simplicity of description. (It is easier to discuss one preferred embodiment than it is to simultaneously describe all possible embodiments.) In the broadest sense, the topsheet may comprise a first component that may be fused to an underlying second component. The second component may be a separate component. Alternatively, the second component could be part of another component, such as part of the topsheet, part of the core, or part of some other component. In still other alternative embodiments, the acquisition component 44 may be omitted entirely. In embodiments where the acquisition component 44 is an integral layer of the core 42 or omitted entirely, the topsheet 38 may be considered to be fused to part of the absorbent core 42. In embodiments without an acquisition component 44, the absorbent core 42 can be comprised of at least some types of fibers (preferably synthetic fibers) that the topsheet 38 can be fused to. A sufficient amount of these fibers are preferably located near the body-facing surface of the absorbent core 42 to facilitate the fusion. Alternatively, if the absorbent core (or other underlying component) comprises powder binder, the topsheet 38 can be fused to the powder binder in the absorbent core 42 (or such underlying component).

In the preferred embodiment shown in the drawings, the acquisition component 44 is preferably joined to the apertured film topsheet 38 by integrity bonding of the faces of the apertured film 38 and acquisition component 44. These components are bonded across a region of their surfaces that forms a "bonded region" 50 on the body-facing side

20A of the sanitary napkin 20. The topsheet 38 and the acquisition component 44 are preferably bonded at a plurality of discrete bonded areas (or "integrity bonds") 52. (However, it is also possible for one or more of the individual integrity bonds 52 to contact each other so that they are not spaced apart and discrete.) In the embodiment shown in FIG. 1, the integrity bonded areas 52 are preferably spaced apart and distributed over the body-facing side 20A of the sanitary napkin 20, with the exception of a portion thereof that defines an unbonded window 54 in a liquid receiving zone of the sanitary napkin.

The discrete integrity bonded areas preferably comprise fusion bonds 52. The fusion can be accomplished by heat and/or pressure bonds, ultrasonic bonds, dynamic mechanical bonds, and the like. Pressure can be applied in any suitable manner, such as by moving the components to be bonded between counter-rotating rolls, placing the materials on an anvil and forcing a platen down on the materials, applying vacuum pressure, and the like. Suitable means that can be adapted for use in fusing the topsheet 38 to the acquisition component 44 are described in at least some of the following patents: U.S. Patent 4,430,148 Schaefer; U.S. Patent 4,515,595 Kievit, et al.; U.S. Patent 4,531,999 Persson, et al.; U.S. Patents 4,710,189 and 4,808,252 issued to Lash; U.S. Patent 4,823,783 Willhite, Jr., et al.; and U.S. Patents 4,854,984 and 4,919,756 issued to Ball, et al.; and in allowed U.S. Patent Application Serial No. 07/944,764 filed in the name of Cree, et al. on September 14, 1992, the parent application which published June 24, 1993 as PCT Publication No. WO 93/11725.

The fusion bonding preferably comprises a plurality of individual fusion bonds 52 that are arranged in a pattern. The integrity bonds 52 can be arranged in many different patterns. FIG. 1 shows one preferred bonding pattern. Other preferred bonding patters are shown in U.S. Patents Des. 399,310; Des. 399,953; Des. 403,763; Des. 403,764; and Des. 403,765. The individual integrity bonds 52 that make up the pattern can be of any plan view shape. For instance, the bonds 52 can be in the form of straight or curved lines, geometric shapes such as circles, squares, rectangles, diamonds, and the like, or irregular shapes. In this embodiment, the integrity bonds 52 comprise a plurality of circular bonds.

A more complete description of the integrity bonds 52 which may be incorporated into an absorbent article of the present invention is found in PCT Publication No.

98/27904 published on July 2, 1998 in the name of Lynard, et al. The use of an unbonded window 54 of integrity bonds such as that shown in FIG. 1 is also a preferred feature as described in the above referenced PCT Publication No. 98/27904. The use of integrity bonding over the body- facing side 20A provides several advantages. The bonding of the topsheet to underlying absorption layers maintains an absorbent component in constant contact with the topsheet for improved acquisition. It also prevents the topsheet from separating from the underlying absorbent component and moving into the crevices in the wearer's body to cause discomfort.

In addition, the unbonded window 54 provides the body-facing side 20A of the sanitary napkin 20 with a region in the liquid receiving zone that is free of bonded areas to eliminate any interference with the acquisition of liquids caused by the presence of the bonds and to maximize the liquid handling capability of the sanitary napkin.

While the use of integrity bonds 52 between the topsheet 38 and one or more underlying components such as an acquisition component 44 is preferred, such is not necessary in order to practice the improved crimp seal of the present invention. Nevertheless, the use of such integrity bonding 52 may result in more stress on the topsheet 38 during manufacture and/or use of the absorbent article. Therefore, the benefits of the improved crimp seal of the present invention may be more pronounced when used in conjunction with such integrity bonding 52 of the absorbent article.

The absorbent core 42 lies between the topsheet 38 and backsheet 40. Preferably, the absorbent core 42 lies under the acquisition component 44, if such is used. The absorbent core 42 may be any absorbent means that is capable of absorbing or retaining liquids (e.g., menses and/or urine). The absorbent core 42 has a body-facing surface, a garment-facing surface, side edges, and end edges. Collectively, the edges of the absorbent core 42 make up the outer boundary 53 of the core 42. The absorbent core 42 may be manufactured in a wide variety of sizes and shapes (e.g., rectangular, oval, hourglass, dog bone, asymmetric, etc.). In the preferred embodiment shown in FIG. 1 of the drawings, the absorbent core 42 is rectangular and is of a size that is slightly smaller than the periphery of the acquisition component 44. In the embodiment shown in FIG. 4, the absorbent core 42 is dog bone shaped, and is larger than the acquisition component 44.

The absorbent core 42 can be manufactured from a wide variety of liquid-absorbent materials commonly used in sanitary napkins and other absorbent articles. Examples of suitable absorbent materials include comminuted wood pulp which is generally referred to as airfelt; creped cellulose wadding; meltblown polymers including coform; chemically stiffened, modified or cross-linked cellulosic fibers; synthetic fibers such as crimped polyester fibers; peat moss; tissue including tissue wraps and tissue laminates; absorbent foams; absorbent sponges; superabsorbent polymers; absorbent gelling materials; or any equivalent material or combinations of materials, or mixtures of these. The configuration and construction of the absorbent core may also be varied (e.g., the absorbent core may have varying caliper zones (e.g., profiled so as to be thicker in the center), hydrophilicity gradients, superabsorbent gradients, or lower density and lower average basis weight acquisition zones; or may comprise one or more layers or structures). The total absorbent capacity of the absorbent core should, however, be compatible with the design loading and the intended use of the sanitary napkin. Further, the size and absorbent capacity of the absorbent core may be varied to accommodate different uses such as incontinence pads, pantiliners, regular sanitary napkins, or overnight sanitary napkins.

In the preferred embodiment shown in the drawings, the absorbent core 42 preferably comprises a multi-bonded air laid material. In this preferred embodiment, this multi-bonded air laid material comprises about 50% to about 70%> cellulose fibers, about 12%) to about 20%> bi-component fibers, about 10%> to about 30% superabsorbent hydrogel-forming material (or absorbent gelling material) particles, and about 3% latex. The absorbent core 42 preferably has a caliper of about 1.5 mm under a pressure of 68.9 Pascals, and a basis weight of about 125 g/yd^ (about 150 g/m^), including the particles of absorbent gelling material (although much higher basis weight materials can also be used). Preferably, this multi-bonded air laid absorbent core 42 is formed by depositing three streams of cellulose and bi-component fibers, with absorbent gelling material particles 58 laid down with the last stream of fibers to form the bottom portion of the absorbent core. In such structures, the absorbent core 42 may be formed as a laminate or, preferably, the fibers may be blended together to form a single web. Such a multi-bonded air laid material is preferably obtained in roll form as product 915000X313 from Merfin Hygienic Products.

In alternative embodiments, the multi-bonded air laid material used for the absorbent core can be bonded using some material other than latex (such as starch or PVA, for example). In another alternative embodiment, the absorbent core can be formed as a laminate that preferably also has a basis weight of about 150 g/m^ and comprises two (or more) layers of multi-bonded air laid nonwoven material with the particles of absorbent gelling material therebetween. Suitable laminate absorbent core structures are described generally in U.S. Patents 4,950,264 and 5,009,653 issued to Osborn, U.S. Patent 5,460,623 issued to Emenaker, et al. Another suitable absorbent core is described in U.S. Patent Application Serial No. 08/122,114, entitled "Sanitary Napkin Having Core Predisposed To A Convex Upward Configuration", filed in the name of Hines, et al. on September 16, 1993 (PCT Publication No. WO 95/07674, published March 23, 1995).

In the above embodiments, or in other alternative embodiments, the absorbent core 42 can be provided with a feature to further improve its flexibility. Such a feature could include, but is not limited to one or more slits, perforations, embossments, or score lines in the absorbent core 42 or acquisition component 44. This type of feature is preferably arranged to improve flexibility about the principal longitudinal centerline L of the sanitary napkin. The slits, perforations, embossments, or score lines can be in any suitable configuration. Suitable configurations include, but are not limited to straight or curved lines, slits, dots, V-shaped patterns, W-shaped patterns, or the like. The slits, perforations, embossments, or score lines, or any combination thereof can be provided in any of the layers of the laminate absorbent cores described above. One example of a feature that will improve the flexibility of the absorbent core 42 is a score line in the absorbent core that runs along the principal longitudinal centerline L of the sanitary napkin 20.

In the case of thicker sanitary napkins, the absorbent core 42 is preferably comprised of airfelt. Suitable absorbent cores for thicker sanitary napkins are described in U.S. Patent 5,234,422 issued to Sneller, et al. In a preferred embodiment, the topsheet 38, acquisition component 44, and absorbent core 42 can be provided with embossed channels as shown in the Sneller, et al. patent.

The backsheet 40 prevents the exudates absorbed and contained in the absorbent core 42 from wetting articles which contact the sanitary napkin 20 such as pants, pajamas and undergarments. The backsheet 40 is preferably resistant to the flow of liquids, and more preferably is impervious to liquids (e.g., menses and/or urine). The backsheet 40 is preferably manufactured from a flexible material. As used herein, the term "flexible" refers to materials which are compliant and will readily conform to the general shape and contours of the human body. The backsheet 40 may comprise a woven or nonwoven material, polymeric films such as thermoplastic films of polyethylene or polypropylene, or composite materials such as a film-coated nonwoven material. Preferably, the backsheet 40 is a polyethylene film having a thickness of from about 0.012 mm (0.5 mil) to about 0.051 mm (2.0 mils). The backsheet 40 may be embossed and/or matte finished to provide a more clothlike appearance. Further, the backsheet 40 may permit vapors to escape from the absorbent core 42 (i.e., breathable) while still preventing exudates from passing through the backsheet 40. A suitable backsheet material is obtained as product No. 18-1401 from the Clopay Corporation of Cincinnati, Ohio. A suitable breathable backsheet material is a laminate of an apertured film such as that described in U.S. Patent 3,929,135 issued to Thompson which is inverted so that the smaller openings of the tapered capillaries face the absorbent core 42 which is adhesively laminated to a microporous film such as that described in Exxon's U.S. Patent 4,777,073.

The topsheet 38, the backsheet 40, the absorbent core 42 (and any additional components such as an acquisition component 44) are assembled in a sandwich construction such as is shown in FIGS. 1-2. In FIG. 1-2, the topsheet 38 and the backsheet 40 have length and width dimensions generally larger than those of the absorbent core 42. The topsheet 38 and the backsheet 40 extend beyond the edges of the absorbent core 42 to form portions of the periphery 30. The garment-facing side of the topsheet 38 is preferably joined to the body-facing side of the acquisition component 44 as described above. The acquisition component 44 may be joined to the absorbent core 42, if desired. If these components are joined, they can be joined in any suitable manner. However, in the embodiment shown in the drawings, the acquisition component 44 is not directly joined to the absorbent core 42. The backsheet 40 is preferably joined to the garment- facing side of the absorbent core by adhesives.

The portions of the topsheet 38 and backsheet 40 that extend beyond the outer boundary 53 (or edges) of the absorbent core 42 are joined to each other using the improved crimp seal of the present invention. The term "joined", as used in this specification, encompasses configurations in which an element is directly secured to another element by affixing the element directly to the other element; configurations in which the element is indirectly secured to the other element by affixing the element to intermediate member(s) which in turn are affixed to the other element; and configurations in which one element is integral with another element, i.e., one element is essentially part of the other element. In preferred embodiments of the present invention, the topsheet 38 is directly joined to the backsheet 40. Additionally, in such preferred embodiments it is desirable to avoid the absorbent core 42 or other components from entering the space at which the topsheet 38 and backsheet 40 will be bonded together.

In a preferred embodiment of the crimp seal of the present invention, the topsheet 38 and backsheet 40 are joined to each other at least partially around the periphery of the absorbent article. In the embodiment shown in FIGS. 1-2, the topsheet 38 and backsheet 40 are joined together at a pair of end crimp regions 55. The topsheet and backsheet 40 are bonded together using a plurality of discrete bonding sites such as crimp bond sites 57. The crimp bond sites 57 are a plurality of individual discrete locations at which the topsheet 38 and backsheet 40 are bonded together through the application of heat and pressure. Preferably, both the topsheet 38 and the backsheet 40 comprise thermoplastic materials which are amenable to such crimp bonding. The discrete bond sites 57 may be more or less continuous over the entire bonding region (such as end crimp regions 55) or some unbonded locations may be present. The density of the bond sites 57 may be uniform in the area of the bonded regions or may vary.

In the embodiments shown most closely in FIGS. 3 and 5, the bond sites 57 are more or less uniformly distributed in the bonded region. In alternative embodiments, the bond sites 57 may be non-uniformly distributed, such that some areas or lower bond density, or even some bond free areas are present within the general bonded region. For example, the area of the bonded region nearest the inner edge of the bonded region may have some areas with no bond sites in order to provide localized areas of tensile strength. Some examples of bonded regions with unbonded locations 61 are shown in FIGS. 6-8.

In the sanitary napkin 20 shown in FIG. 1, each of the end crimp regions 55 is preferably 2 or more mm wide, more preferably, from about 2 to about 10 mm wide. The crimp bond sites 57 are preferably present in a density of about 175 to about 275 bonds per square inch, more preferably about 225 to about 250 bonds per square inch. Each bond site 57 may have a size of about 0.0016 in². Preferably, the distance from one bond site to the next adjacent bond site (measured from the center of each site) is less than about 0.1 inches.

Any suitable technique may be used to form the discrete bonds 57 of the crimp seal of the present invention. Typically, the discrete bond sites 57 are created through the use of a system of two counter rotating cylindrical rolls defining a nip therebetween. One roll is machined into a pattern roll containing raised projections corresponding to the desired plan shape of each of the bond sites. These projections are also machined in the offset pattern of the crimp seal of the present invention. The other roll is an anvil roll designed to act as a surface for the pattern roll to press the absorbent article against during formation of the crimp seal. The pressure and temperatures chosen will vary somewhat depending on the materials used for the topsheet and the backsheet. In the embodiment shown in FIG. 1 the backsheet comprises a polyethylene film and the topsheet comprises a formed film of linear low density polyethylene and low density polyethylene. In such an embodiment, the bond sites 57 may be formed using a temperature in the range from about 200°F to about 350°F and a pressure in the range from about 29 psig to about 58 psig.

The crimp bond sites 57 may be the only method of attachment of the topsheet 38 and the backsheet 40, or other supplemental attachment methods such as an adhesive may also be used. Other suitable supplemental techniques for joining the topsheet 38 and backsheet 40 include ultrasonic bonding, heat sealing, or any other means known in the art. Any of the methods described above for creation of the integrity bonds 52 are also suitable for creation of the crimp bonds 57 of the present invention. In the preferred embodiment shown in FIG. 1, no supplemental bonding method other than the crimp bond sites 57 is necessary in the end crimp regions 55.

As shown more closely in FIG. 3, each of the discrete crimp bond sites 57 has a plan view which is in the shape of a simple closed figure with rounded sides. In the preferred embodiment shown in FIG. 3, each of the discrete bonds 57 comprises a circular plan view shape. This avoids the use of shapes with shaφ corners such as a square which may result in undesirable stress concentration points at such corners. Other plan view shapes with rounded sides such as the oval shape shown more closely in FIG. 5 are also suitable for the discrete bonds sites 57 of the present invention. The lack of shaφ corner also may allow for higher temperatures during formation of the bond sites 57 than would otherwise be possible.

Each of the discrete crimp bond sites 57 is preferably offset with respect to the next adjacent bond site. As can be seen more closely in FIGS. 3 and 5, rows of the bond sites 57 are staggered with respect to one another. Such staggering may be done in the longitudinal direction, in the transverse direction, in both the longitudinal and transverse directions, or in some other combination. FIG. 3 shows an embodiment in which the discrete crimp bond sites 57 are arranged in rows which follow the contour of the periphery 30 of the main body portion 22. Each row is staggered in the transverse direction (at the end 28 of the sanitary napkin 20) with respect to the next adjacent row. Such an arrangement acts to prevent any perforations which may form from propagating in the longitudinal direction. Preferably, the amount of stagger is about one-half to about two-thirds the size of an individual bond site 57. In other variations, differing amounts of stagger from one row of bond sites to the next may also be employed.

In particularly preferred embodiments of the present invention, care is taken to ensure that the innermost portion of the end crimp region 55 contains a row of complete discrete bond sites 57. In other words, partial bonds (such an one-half of a complete circular bond) are avoided. This reduces the likelihood that such "half-crimped" locations can serve as the basis for a perforation to propagate in the transverse direction and result in opening of the crimp seal.

The crimp sealing of the topsheet 38 to the backsheet 40 may be located at selected locations of the article such as at end crimp regions 55, or may be located around the entire periphery of the article. FIG. 4 shows an alternate sanitary napkin 20 in which the crimp seal of the present invention is located in a bonding region 59 which extends around the entire periphery 30 of the article. The sanitary napkin 20 shown in FIG. 4 is a type which does not contain flaps such as those shown in the napkin of FIG. 1. Nevertheless, a sanitary napkin with flaps may be provided with a crimp seal of the present invention in a bonding region 59 which extends around its entire perimeter. Similarly, a sanitary napkin without flaps may be provided with a crimp seal around only portions of its perimeter. Preferably, if the crimp seal of the present invention is provided around only a portion of the perimeter of the absorbent article (such as at end crimp regions 55), some portion of the remainder of the article is sealed with other means. In the embodiment shown in FIG. 1, the layers which comprise the flaps 24 are joined with a suitable adhesive. It may also be desirable to use a "glue free window" at a suitable location in the flaps 24 as is described in PCT Publication WO 98/27904 published on July 2, 1998 in the name of Lynard, et al.

The sanitary napkin 20 shown in FIGS. 1-2, as discussed above, comprises an optional pair of flaps 24 that are joined to the main body portion 22. The flaps 24 extend laterally outward beyond the longitudinal side edges 26 of the main body portion 22 from their proximal edges 60 to their distal edges (or "free end") 62. The flaps 24 extend outward from at least the central region 36 of the main body portion 22.

The flaps 24 can be joined to the main body portion 22 in any suitable manner.

Preferably, in the embodiment shown in FIGS. 1-2, the flaps 24 are integral with the main body portion 22 (that is, the flaps 24 comprise integral extensions of the topsheet 38 and backsheet 40). In other alternative embodiments, the flaps 24 can comprise separate components that are joined to the main body portion 22. The flaps 24 are each joined to (or associated with) main body portion 22 along a juncture. This is typically a longitudinally-oriented (or "longitudinal") juncture, such as lines of juncture 68. As used herein, the terms "juncture" (or "line of juncture") refer to regions where the flaps 24 extend from or are joined to the main body portion 22. The line of juncture 68 in the embodiment illustrated in the drawings can be considered to be defined by concave inwardly-oriented regions or lines.

The flaps 24 can be in any suitable configuration. Suitable flaps are described in Reexamined Patent No. Bl 4,589,876 entitled "Sanitary Napkin", issued to Van Tilburg, Certificate of Reexamination issued April 27, 1993; U.S. Patent 4,687,478 entitled "Shaped Sanitary Napkin With Flaps", which issued to Van Tilburg on August 18, 1987; U.S. Patent 5,389,094 entitled "Absorbent Article Having Flaps and Zones of Differential Extensibility" issued to Lavash, et al. on February 14, 1995; U.S. Patent 5,558,663 entitled "Absorbent Article Having Undergarment Covering Components With Zones of Extensibility" issued to Weinberger, et al. on September 24, 1996 (which describes an alternative to flaps that are applied by the wearer); and in International Patent Application Serial No. PCT US 96/15957 entitled "Absorbent Article Having Flaps With Step Configuration and Zones of Extensibility" filed on October 3, 1996, in the name of Lash, et al. Particularly preferred flaps and the associated features, characteristics, and properties of such are described in PCT Publication WO 98/27904 published on July 2, 1998 in the name of Lynard, et al.

The garment surface 20B of the sanitary napkin 20 may include, and preferably does include, fasteners for attaching the sanitary napkin to the wearer's undergarment. Figure 2 shows the central pad fastener 82 which is adapted to secure the main body portion 22 of the sanitary napkin to the crotch region of an undergarment. Any types of fasteners known in the art, such as adhesive fasteners and mechanical fasteners can be used. Fasteners comprising adhesives have been found to work well for this puφose, with pressure-sensitive adhesives being preferred. In a preferred embodiment, the central pad fastener 82 comprises a pair of spaced apart longitudinally-oriented strips or zones of adhesive that are centered about the longitudinal centerline L.

The outer surface of the flaps 24, adjacent the distal edges 62 of the flaps, is preferably provided with a flap adhesive 84. The flap adhesive 84 is used to assist in maintaining the flaps 24 in position after they are wrapped around the edge of the crotch portion of the panty. Suitable adhesive fasteners are described in greater detail in U.S. Patent 4,917,697. The flaps 24 can be maintained in position by attaching the flaps 24 to the undergarment, or to the opposing flap.

The fasteners used with the present invention are not limited to adhesive attachment means. Any type of fastener used in the art can be used for such puφose. For example, the sanitary napkin 20 could be secured to the wearer's undergarment by mechanical fasteners, such as VELCRO, or the fasteners described in U.S. Patent 4,946,527 entitled "Pressure-Sensitive Adhesive Fastener and Method of Making the Same" issued to Battrell on August 7, 1990, or U.S. Patent 5,392,498 entitled "Non- Abrasive Skin Friendly Mechanical Fastening System" issued to Goulait, et al. on February 28, 1995. For simplicity, however, the fasteners will be described in terms of adhesive attachment means.

The adhesive attachment means are respectively covered by removable release liners, central pad release liner and flap release liner, both designated 86. The pressure- sensitive adhesives should be covered with release liners 86 to keep the adhesives from sticking to extraneous surfaces prior to use. Suitable release liners are described in U.S. Patent 4,917,697. A particularly preferred release liner which also serves as an individual package for wrapping the sanitary napkin is described in U.S. Patent 4,556,146 issued to Swanson, et al.

The sanitary napkin 20 of the present invention is utilized by removing the release liners 86 and placing the sanitary napkin 20 in a panty. The main body portion 22 is placed in the crotch portion of the panty with one end of the main body portion 22 extending towards the front section of the panty and the other end towards the back section of the panty. The backsheet 40 is placed in contact with the inner surface of the center of the crotch portion of the panty. The central pad adhesive fastener 82 maintains main body portion 22 in position. The distal portions of the flaps 24 are folded around the side edges of the panty. The flap adhesives 84 secure the flaps 24 to the underside of the panty or to the opposing flap.

The disclosures of all patents, patent applications (and any patents which issue thereon, as well as any corresponding published foreign patent applications), and publications mentioned throughout this patent application are hereby incoφorated by reference herein. It is expressly not admitted, however, that any of the documents incoφorated by reference herein teach or disclose the present invention. It is also expressly not admitted that any of the commercially available materials or products described herein teach or disclose the present invention.

While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention.

Claims

WHAT IS CLAIMED IS:

1. A disposable absorbent article having a pair of longitudinal side edges and a pair of end edges forming the periphery of said article, said absorbent article further having a length in a longitudinal direction and a width in a transverse direction, said absorbent article comprising:

an absorbent core, said absorbent core having a body facing surface, a garment facing surface and an outer boundary;

a substantially liquid impervious backsheet overlaying said garment facing surface of said absorbent core and extending beyond at least a portion of said outer boundary thereof;

a thermoplastic formed film liquid pervious topsheet overlaying said body facing surface of said absorbent core and extending beyond at least a portion of said outer boundary thereof, said backsheet being at least partially peripherally joined to said topsheet characterized in that said absorbent article further comprises

a plurality of discrete bonding sites for joining said topsheet to said backsheet, each of said discrete bonding sites having the plan view shape of a simple closed figure with rounded sides, wherein each of said plurality of discrete bonding sites is offset with respect to the next adjacent bond site in at least one of the longitudinal direction or the transverse direction.

2. The absorbent article of Claim 1 wherein each of said discrete bond sites comprises a circular or oval shape.

3. A sanitary napkin having a pair of longitudinal side edges and a pair of end edges forming the periphery of said sanitary napkin, said sanitary napkin further having a length in a longitudinal direction and a width in a transverse direction, characterized in that said sanitary napkin comprises:

an absorbent core, said absorbent core having a body facing surface, a garment facing surface and an outer boundary; a substantially liquid impervious backsheet overlaying said garment facing surface of said absorbent core and extending beyond at least a portion of said outer boundary thereof;

a liquid pervious topsheet preferably comprising a thermoplastic formed film material said topsheet overlaying said body facing surface of said absorbent core and extending beyond at least a portion of said outer boundary thereof, said backsheet being at least partially peripherally joined to said topsheet; and

4. The sanitary napkin of Claim 5 wherein said plurality of discrete bonding sites occupy a bond area said bond area having a width not greater than 10mm.

5. The sanitary napkin of Claim 5 wherein said plurality of discrete bonding sites have a maximum distance from one such discrete bonding site to said next adjacent bonding site of not greater than 0.04 in.

6. The sanitary napkin of Claim 1 or 5 wherein said liquid impervious backsheet comprises a thermoplastic film.

7. The sanitary napkin of Claim 5 wherein said topsheet and said backsheet are joined together solely through the application of said discrete bonding sites without the need for a supplemental adhesive.

8. The sanitary napkin of Claim 5 wherein said discrete bonding sites have a bond density in the range of from about 175 to about 275 bonds per square inch.

9. The sanitary napkin of Claim 5 wherein said discrete bonding sites are located over a bonding area, said bonding area having a substantially uniform bond site density over said entire bonding area.

0. A sanitary napkin having a pair of longitudinal side edges and a pair of end edges forming the periphery of said sanitary napkin, said sanitary napkin further having a length in a longitudinal direction and a width in a transverse direction, said sanitary napkin comprising:

a liquid pervious topsheet overlaying said body facing surface of said absorbent core and extending beyond at least a portion of said outer boundary thereof, said backsheet being at least partially peripherally joined to said topsheet; characterized in that said sanitary napkin further comprises

a plurality of discrete bonding sites for joining said topsheet to said backsheet, each of said discrete bonding sites having the plan view shape of a simple closed figure with rounded sides, wherein said discrete bonding sites are located over a bonded region, and wherein said bonding region is free from partially formed discrete bonding sites.