# Patent

## Title
Dark colored absorbent articles

## Abstract

Dark colored absorbent articles, such as pantiliners or sanitary napkins. More specifically, dark colored absorbent articles are disclosed comprising an apertured topsheet, an underlying layer visible through the apertures of the topsheet and a backsheet, wherein both the topsheet and underlying layer have a L Hunter value of less than 60. Preferably the topsheet, the backsheet and the underlying layer have the same color (e.g., black).

## Background
CROSS REFERENCE TO RELATED REFERENCES
This is a continuation of International Application PCT/US01/22786 with an International filing date of Jul. 19, 2001.


FIELD OF THE INVENTION
The present invention relates to dark colored disposable absorbent articles, in particular sanitary napkins and panty liners.
The absorbent articles according to the present invention have the benefit of not becoming easily apparent by visual inspection when they are worn with dark colored undergarments (e.g. black, gray, navy blue and the like).
BACKGROUND OF THE INVENTION
It has historically been common that absorbent articles, in general including diapers, adult incontinence products, underarm sweat products, collar inserts, sanitary napkins and pantiliners are provided in a color communicating a hygienic condition. This conventionally resulted in white or predominantly white articles. This did fit well with the historically predominant undergarment color in which these articles are worn, namely white undergarments. As a result white pantiliners or white sanitary napkins are not easily recognizable when used in such white undergarments.
Very recently fashion has led women more frequently to use other colors than white undergarments. This has been dictated not only by fashion itself but also as a result of the development of clothing which has a certain translucency and allows the color of the undergarment to be recognized. Furthermore very recently so-called G-String undergarments or “Tanga-Slips” have become widely used in particular by a younger generation women. These so-called string tangas are particularly used to prevent easy recognition of the contour of the undergarment through tight fitting clothes.
It has thus become a need to have sanitary napkins or pantiliners available which match the color of the undergarments (and typically the garments) in order to prevent a color-based recognition of the presence of such articles (under the assumption that modern clothing can be translucent).
For sanitary napkins or pantiliners having so-called wings which are folded around the outside of the undergarment this is even more important since the wing part of the sanitary napkin or pantiliner is on purpose folded onto the outside of the undergarment and therefore easily visible, depending on the clothing worn over the undergarment.
Sanitary towels comprising an absorbent material and a backsheet (side directed towards the garment), which is skin tone coloured are disclosed in Fl 9602361 to Anja Levoranta. The coloring can simulate the real skin colour. DE 19821821 to Buetow Geb Wantulla, discloses pantiliners that can be separated in two tanga pantiliners along their diagonal line. They are preferably produced in a variety of different colors. Indeed, the topsheet and the backsheet of these pantiliners might be colored.
Traditionally the absorbent cores used in absorbent articles, like pantiliners and/or sanitary napkins, are available in white color to communicate a hygienic condition. However, it has now been observed that the use of such white absorbent cores in dark colored absorbent articles provided with dark colored so called “apertured topsheet” conflicts with the need of discretion in use of such articles, as the white color would be visible through the apertures of the dark colored topsheet.
It is thus an object of the present invention to provide absorbent articles, like pantiliners and/or sanitary napkins, being discreet in use when worn with a dark colored undergarment. It is a further object of the present invention to provide absorbent articles, particularly sanitary napkins or pantiliners, which are made such that when worn they are not easily recognizable on dark colored undergarments or more generally under translucent garments in which they are worn, which are simple and cheap to mass manufacture.
This has now been achieved by providing an absorbent article having an apertured topsheet, an underlying layer visible through the apertures of the topsheet and a backsheet, wherein both the topsheet and underlying layer have a color L Hunter value of less than 60. Preferably the difference in L Hunter value ΔL between the underlying layer (e.g., secondary topsheet and/or absorbent core) and the topsheet is less than 20.
Advantageously a masking effect of the absorbent core typically of light color (white color) is provided, which is hence not recognizable through the apertures of the topsheet, thereby providing discretion in use of the entire absorbent article of the present invention. Masking the absorbent core in dark colored absorbent articles provides enhanced discretion in use, especially in more intimate moment of woman life, where the woman may have to remove her undergarment.
Another benefit associated to the dark colored absorbent articles according to the present invention in use is the masking effect of the bodily discharge absorbed and retained in the absorbent articles. Bodily fluids like vaginal secretions, urine lost and/or menstruation will be masked by the presence of an underlying layer (e.g., secondary topsheet and/or absorbent core) having a L Hunter value of less than 60, preferably matching the color of the topsheet of the absorbent articles of the present invention. This contributes to overall comfort and discretion. Indeed optimum masking of any bodily fluid discharge especially menstrual blood discharge, into the absorbent article, is achieved when both the topsheet and the underlying layer have a L hunter value of less than 30 and are preferably of black color.
In one embodiment herein the absorbent articles of the present invention might comprise in their absorbent core odor control materials like for instance active carbon, which is from far one of the most active and cost effective odor control material. This odor control material was traditionally not desired in conventional hygienic white absorbent articles due to its inherent black color. Active carbon (also called charcoal) might advantageously be used in the dark colored absorbent articles of the present invention especially the black ones, without impairing on the comfort and discretion of the article.
SUMMARY OF THE INVENTION
The present invention encompasses an absorbent article comprising an apertured topsheet, an underlying layer visible through the apertures of the topsheet and a backsheet, wherein the topsheet and the underlying layer independently have a L Hunter value of less than 60, when defined according to the Hunter Color system as described herein after.



BRIEF DESCRIPTION OF THE DRAWINGS
The invention is further described with reference to the accompanying drawings.
FIG. 1 is a top plan view of a preferred black pantiliner according to the present invention, the topsheet facing the viewer (darkness/color not shown).
FIG. 2 is an enlarged lateral cross sectional view of a pantiliner according to the present invention.
FIG. 3 is an enlarged lateral cross-sectional view taken along line I-I of FIG. 1.
FIG. 4 is an enlarged lateral cross sectional view of another pantiliner according to the present invention.
FIG. 5 is a top plan view of another preferred black pantiliner according to the present invention, namely a thong pantiliner, the topsheet facing the viewer.
FIG. 6 is a top plan view of a black thong pantiliner according to the present invention, the topsheet facing the viewer, the topsheet being provided with a series of bonding locations 1 at which the topsheet is bonded at least partially to the respective underlying layer in line with the teaching of EP-A-617 602. (darkness/color not shown)



DETAILED DESCRIPTION OF THE INVENTION
Definitions
“Absorbent articles” as referred to herein are primarily sanitary napkins, pantiliners, or incontinence pads that are worn in the crotch region of an undergarment. However, articles such as sweat-absorbent underarm pads, nursing pads or collar inserts can also benefit from the present invention. It is even conceivable that baby diapers, adult incontinence diapers, and human waste management devices benefit from the present invention even though they are conventionally not worn in conjunction with an undergarment.
The term ‘disposable’ is used herein to describe absorbent articles that are not intended to be launched or otherwise restored or reused as absorbent articles (i.e., they are intended to be discarded after a single use and, preferably to be recycled, composted or otherwise disposed of in an environmentally compatible manner).
The absorbent article according to the present invention is conventionally constructed of three main elements: The topsheet, facing the user of the article during use and being liquid pervious in order to allow liquids to pass into the article, the topsheet is an apertured topsheet; the backsheet, providing liquid containment such that absorbed liquid does not leak through the article, this backsheet conventionally provides the garment facing surface of the article; a layer underlying the apertured topsheet, said layer being visible trough the apertures of the topsheet. Preferably such underlying layer is provided by at least a portion of a secondary layer also called herein secondary topsheet and/or at least a portion of an absorbent core sandwiched between the topsheet and the backsheet and providing the absorbent capacity of the article to acquire and retain liquid which has entered the article through the topsheet. In some embodiments as described herein after, the underlying layer might be provided by at least a portion of the backsheet and/or by at least a portion of an intermediate layer positioned between the absorbent core and the backsheet.
Many absorbent articles and constructions, including particular materials, are known in the art and have been described in ample detail over time. All of such materials are useful in the context of the present invention, provided that they meet the dark color requirement as defined herein by the Hunter color scale values. Typically this will require only moderate modification of the material composition while maintaining the majority of the conventional material characteristics. In the following, examples of materials, which are particularly beneficial for the use in the absorbent articles according to the present invention, are mentioned. Those skilled in the art will readily be able to identify alternative materials, which can also be used in the context of the absorbent articles according to the present invention.
According to the present invention the topsheet and the underlying layer of the absorbent articles independently have an L Hunter value of less than 60.
The L Hunter scale values, utilized herein to define the darkness/lightness of the materials of the absorbent articles according to the present invention, are units of color measurement in the Hunter Color system. A complete technical description of the system can be found in an article by R. S. Hunter, ‘photoelectric color difference Meter’, Journal of the Optical Society of America, Vol. 48, pp.985-95, 1958. Devices specially designed for the measurement of color on the Hunter scales are described in U.S. Pat. No. 3,003,388 to Hunter et al., issued Oct. 10, 1961. In general, Hunter Color “L” scale values are units of light reflectance measurement, and the higher the value is, the lighter the color is since a lighter colored material reflects more light. In particular, in the Hunter Color system the “L” scale contains 100 equal units of division, absolute black is at the bottom of the scale (L=0) and absolute white is at the top of the scale (L=100). Thus in measuring Hunter Color values of the materials used in the absorbent articles according to the present invention, the lower the “L” scale value, the darker the material.
The absorbent articles herein, and hence the materials of which the absorbent articles are made of, might be of any color provided that the L Hunter value defined herein is meet.
‘Color’ as referred to herein include any primary color, i.e., white, black, red, blue, violet, orange, yellow, green, and indigo as well as any declination thereof or mixture thereof.
Colors can be measured according an internationally recognized 3D solid diagram of colors where all colors that are perceived by the human eye are converted into a numerical code. This system is based on three dimensions (x,y,z) and specifically L*, a*, b*.
When a color is defined according to this system L* represents lightness (0=black, 100=white), a* and b* independently each represent a two color axis, a* representing the axis red/green (+a=red, −a=green), while b* represents the axis yellow/blue (+b=yellow, −b=blue).
Any color is identified by a unique AE value, which is mathematically expressed by the equation:

ΔE=[(L*ref.−L*sample)2+(a*ref.−a*sample)2+(b*ref.−b*sample)2]1/2 

ΔE represents graphically the distance between the reference color and the no color point (i.e. centre of sphere L*ref=50, a*ref=0, b*ref=0) of the 3d model.
Color can be measured using the calorimeter MINOLTA mode CR-300 instrument (available from the Minolta Company, Japan) which provides the coordinates L*, a*, b* and from which the ΔE value can be determined.
It is to be understood that the L Hunter values and color values ΔE considered herein are those measured on the materials of interest (e.g., topsheet or backsheet or underlying layer), taken in layer or folded upon it self, so that upon additional layering of the same material or additional folding thereof, the L Hunter value and color value stay constant. Indeed the L Hunter value and ΔE are those of the material perse without any influence of the support onto which the material is disposed in the instrument for its measure. In other words, when measuring the L Hunter value of for example the apertured topsheet layer, several layers of this material are superposed or a layer thereof is folded upon itself several times before measuring its L Hunter value, the same material is measured again after additional layering or folding, this later operation is performed as needed until upon additional layering or folding the L Hunter value does not change any more. This value is the one to be considered herein.
Topsheet
The term apertured topsheet as used herein refers to topsheets having apertures. In general the apertured topsheet is compliant, flexible, soft feeling and non-irritating to the wearer's skin.
Typically the topsheet comprises a plurality of apertures having a pore size of 0.0001 mm to 5 mm. All apertures might have the same dimensions or apertures of different dimensions might be present. The open area of the apertured topsheet is typically from 1% to 50%, preferably from 5% to 45%, more preferably from 10% to 40% and most preferably from 20% to 35%.
The apertured topsheet is typically an apertured polymeric film. Suitable apertured polymeric film topsheets for use herein include polymeric apertured formed films, apertured formed thermoplastic films, apertured plastic films, and hydroformed thermoplastic films; porous foams; reticulated foams; reticulated thermoplastic films; and thermoplastic scrims.
Apertured formed films are particularly suitable for use herein as the apertured topsheet because they are pervious to body exudates and yet nonabsorbent and have a reduced tendency to allow fluids to pass back through and rewet the wearer's skin. Thus, the surface of the formed film that is in contact with the body remains dry, thereby reducing body soiling and creating a more comfortable feel for the wearer. Suitable formed films are described in U.S. Pat. No. 3,929,135 (Thompson), issued Dec. 30, 1975; U.S. Pat. No. 4,324,246 (Mullane, et al.), issued Apr. 13, 1982; U.S. Pat. No. 4,342,314 (Radel. et al.), issued Aug. 3, 1982; U.S. Pat. No. 4,463,045 (Ahr et al.), issued Jul. 31, 1984; and U.S. Pat. No. 5,006,394 (Baird), issued Apr. 9, 1991. Particularly preferred microapertured formed film topsheets are disclosed in U.S. Pat. No. 4,609,518 (Curro et al), issue Sep. 2, 1986 and U.S. Pat. No. 4,629,643 (Curro et al), issued Dec. 16, 1986.
A formed film which is suitable for use herein is a black polyethylene apertured formed film, black CPM DH® code 45105/99 available from BP Chemicals, Wasserburg-Germany.
The body surface of the polymeric film topsheet can be hydrophilic so as to help liquid to transfer through the topsheet faster than if the body surface was not hydrophilic. In a preferred embodiment, surfactant is incorporated into the polymeric materials of the formed film topsheet such as is described in PCT Publication No. WO93/09741, “Absorbent Article Having A Nonwoven and Apertured Film Coversheet” filed on Nov. 19, 1991 by Aziz, et al. Alternatively, the body surface of the topsheet can be made hydrophilic by treating it with a surfactant such as is described in the above referenced U.S. Pat. No. 4,950,254.
Other suitable apertured topsheet for use herein are made of woven or nonwoven materials or knit materials. Such materials might be comprised 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.
Particularly suitable apertured topsheet for use herein are nonwoven topsheet. Suitable nonwoven materials/layers include fibrous nonwoven materials/layers formed by a carding process or a spunbond process or meltblown process whereby molten polymeric material is extruded through a die, attenuated to lengthen the extruded polymer into fibers and decrease the diameter thereof and is subsequently deposited on a forming surface. Methods of forming such nonwoven materials/layers are known to those skilled in the art. Polymeric materials suitable for use in forming such fibrous nonwoven materials/layers include polyolefins such as polyethylene and polypropylene, polyesters, nylons, ethylene vinyl acetate, ethylene methacrylate, copolymers of the above materials, block copolymers such as A-B-A block copolymers of styrene and butadiene, and the like.
A conventional nonwoven material, which is suitable for use herein, is a black spunbonded polyethylene layer commercially available from BBA under code name T27CXC.
Beside the conventional nonwoven materials described herein before, the apertured topsheet for use herein can be made of conventional nonwoven materials typically provided by any process mentioned herein before like spunbond process, into which additional apertures can be formed by any conventional method known to those skilled in the art for this purpose after the nowoven materials have been formed per se.
In yet a preferred embodiment herein the apertured topsheet comprises an apertured polymeric film, preferably an apertured formed film, together with a nonwoven outer layer (the nonwoven layer being directed towards the wearer surface). Typically the nonwoven layer is disposed onto the apertured polymeric film in a discontinuous way so that at least the region where liquid is expected to be discharged onto the absorbent article is free of the nonwoven layer. Indeed, it is particularly preferred that the topsheet be a so-called hybrid topsheet in which the wearer contacting surface is provided in its longitudinal center by an apertured polymeric film while a region not including the center is provided with a non-woven such as e.g. the high loft non-woven or other non-woven which does provide particularly skin friendliness. Such topsheets have been disclosed in EPA-523 683, EP-A-523 719, EP-A-612 233, or EP-A-766 953. FIG. 1 illustrates a pantiliner 1 with such a preferred topsheet comprising a nonwoven outer layer 2 and an apertured polymeric formed film layer 3 (apertures not shown). The nonwoven outer layer 2 has an opening 20 positioned in the central zone of the wearer facing surface of the absorbent article. The opening 20 is provided in the nonwoven outer layer 2 as a passageway for body exudates to be deposited directly onto the apertured formed film layer 3 to take advantage of its superior fluid handling properties so that fluid will rapidly pass into the absorbent core. Typically the nonwoven outer layer 2 comprises two strips 21, 22, spaced apart on top of the apertured formed layer 3 so that the spaced region between the strips 21, 22 forms the opening 20. The two layers can be continuously, partially or intermittently bonded together. In a preferred embodiment the nonwoven outer layer and apertured formed film layer are spot-bonded at a plurality of positions of the strips 21 and 22 with a heat bond 23. The heat bonds 23 provide an embossed seal pattern that can also convey an aesthetic effect in its pattern design, e.g. undulated lines.
The apertured topsheet herein can be made from a nonwoven or woven material or a polymeric film. Such films and nonwovens or wovens can be made for example from polymers such as polyethylene or polypropylene compositions. Conventionally such polymers have been provided with a coloring material such as titanium dioxide to provide a white opacity. Simply using other coloring materials (e.g., dyes, pigments and so on) namely dark coloring materials (like black, navy bleu, gray and the like) provides a dark colored film or nonwoven. The use of other coloring materials instead of titanium dioxide so as to meet the L Hunter values for the materials to be used herein, has the advantage to not cause any substantial material change. Also selecting particular coloring materials to be used in the material from which the topsheet can be made also provides the additional benefit of better material characteristics (besides less costs and a reduced environment burden).
It is to be understood herein that any conventional method known to those skilled in the art to provide dark colored apertured topsheet (i.e., material meeting the L Hunter value requirement herein) is suitable for use herein. Dark colored topsheet can typically be provided made of any of the materials mentioned above by different methods well known to those skilled in the art, including pigmenting the materials, dying the materials or color printing the materials.
A preferred example of dark colored topsheet is an hybrid topsheet with black polyethylene-based apertured formed film CPM DH® code 45105/99 available from BP Chemicals together with black nonwoven spunbonded polyethylene outer layer available from BBA under code name T27CXC. Both these black materials are obtained by using carbon-based pigments.
According to the present invention the apertured topsheet herein has a L Hunter value of less than 60, preferably less than 50, more preferably less than 40, even more preferably less than 30 and most preferably less than 20. In the embodiment herein wherein different layers are used for the topsheet like an apertured polymeric film layer together with a nonwoven outer layer, all the layers individually match this requirement. Preferably the L Hunter value of the different layers/materials of the topsheet is the same.
In a preferred embodiment the difference in color value ΔE between different layers/materials of the topsheet, for example between the nonwoven outer layer and the apertured polymeric film layer, is preferably less than 30, more preferably less than 15 and most preferably less than 10. Most preferably the colors of the different layers/materials of the topsheet match each other (are the same (i.e., have same ΔE)).
In a highly preferred embodiment the topsheet is black and is typically provided by using carbon-type pigment as the coloring agent.
It has surprisingly been found that the addition of carbon-type pigments like graphite to nonwoven delivers improved softness to the nonwoven. Without to be bound by theory, it is speculated that this softness benefit is most likely due to the fact that the carbon-type pigment, namely graphite, acts as an impurity, lowering the bonding of polymer base material, thereby delivering a fuzzier finished material which is hence softer at skin contact. Hence in a preferred embodiment of the invention, the absorbent articles have a dark colored nonwoven topsheet wherein the color is provided by the presence of carbon-type pigment like graphite. Such absorbent articles having a dark colored nonwoven topsheet wherein darkness is provided by carbon-type pigment are not only more discrete in use when dark colored undergarments are considered but also more comfortable.
Backsheet
In general the backsheet is compliant, flexible and soft feeling. The backsheet prevents the exudates absorbed and contained in the absorbent core from wetting clothes that contact the absorbent article such as undergarments. Preferably the backsheet is impervious to liquids (e.g., menses, sweat and/or urine). It can be manufactured from a thin plastic film, although other flexible liquid impervious materials can also be used. As used herein, the term “flexible” refers to materials that are compliant and will readily conform to the general shape and contours of the human body. The backsheet preferably also can have elastic characteristics allowing it to stretch in one or two directions.
The backsheet can 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 or fiber coated film. Conventionally absorbent articles comprise a backsheet of a polyethylene film having a thickness of from about 0.012 mm to about 0.051 mm.
The backsheet is preferably breathable, i.e., allows the transmission of water vapor, or even more preferable the transmission of air, however without sacrificing its main purpose to provide leakage protection for absorbed liquids. The backsheet can also comprise more than one breathable layer so as to replace a single breathable backsheet layer by at least 2 or 3 layers of a different or the same material. In particular two breathable layers forming together the breathable backsheet are preferred.
Preferably the backsheet of the absorbent articles of the present invention has a L Hunter value of less than 60, more preferably less than 40, even more preferably less than 30 and most preferably less than 20. Preferably the difference of L Hunter value ΔL between the backsheet and the topsheet is less than 20, preferably less than 15 and more preferably less than 10. Preferably the backsheet has the same L Hunter value than the topsheet of the absorbent article.
In a preferred embodiment the difference in color value ΔE between the topsheet and the backsheet is less than 40, preferably less than 30, more preferably less than 20 and most preferably less than 15. Typically the backsheet has the same color (i.e., same ΔE) than the topsheet. In a preferred execution herein the topsheet and the backsheet are black.
According to the present invention a polyethylene backsheet, or in fact any backsheet made from polymeric material can be provided in any color including dark color by using a color filler matching the color of interest. For instance dark colored backsheet might be provided by using the suitable among of a color filler/pigments and preferably a dark color filler/pigment, instead of the conventional white materials like titanium dioxide. As will be recognized by those skilled in the art the dark color of the backsheet can be provided in the same manner as in the dark colored topsheet.
Underlying Layer
The absorbent articles of the present invention comprise as an essential element an underlying layer visible through the apertures of the topsheet.
The underlying layer has an L Hunter value of less than 60, preferably less than 50, more preferably less than 40, even more preferably less than 30 and most preferably less than 20. The difference in L Hunter value ΔL between the topsheet and the underlying layer is typically less than 20, preferably less than 15, more preferably less than 8, even more preferably less than 5, and most preferably less than 3. Preferably the L Hunter value of the underlying layer is the same as those of the topsheet or less than the L Hunter value of the topsheet.
In a preferred embodiment the difference in color value ΔE between the topsheet and the underlying layer is less than 40, preferably less than 30, more preferably less than 20 and most preferably less than 10. In yet a preferred embodiment the color of the underlying layer is the same as those of the topsheet (i.e., same ΔE), preferably black color.
The underlying layer can be provided by a single layer/material or by a plurality of layers/materials. Importantly the underlying layer visible through the apertures of the topsheet is provided by any material directly adjacent to the topsheet and visible through said topsheet. Thus the underlying layer might be provided by different materials/layers in the instance where one single layer/material does not extend through the entire surface adjacent the topsheet.
As for the topsheet and backsheet any conventional method known to those skilled in the art for providing dark colored underlying layer is suitable for use herein.
In one embodiment of the present invention the underlying layer is provided by at least a portion of a secondary layer (also called secondary topsheet). Such a secondary layer might be manufactured from a wide range of materials such as woven, nonwoven materials, polymeric materials such as apertured formed thermoplastic films, apertured plastic film, hydroformed thermoplastic films, porous foams, reticulated foams, reticulated thermoplastic films and thermoplastic scrims. Any material described herein before for the topsheet can be used for the secondary layer.
In a preferred embodiment, the underlying layer is provided by a secondary layer, this secondary layer preferably underlying the apertured topsheet on the entire surface thereof, i.e., the secondary layer extends to the periphery of the topsheet so that the secondary layer underlies the topsheet on the entire surface of the topsheet. This secondary layer is positioned between the absorbent core and the apertured topsheet like for example an apertured polymer film and/or nonwoven. In this preferred embodiment the secondary layer is able to mask any further underlying layer whatever its color, including for example light colored absorbent core having a L hunter value of 65 or higher, preferably more than 70 and more preferably more than 80, like conventional white absorbent core. Advantageously such an execution provides in a timely and cost effective manner a dark colored article, with dark colored apertured topsheet and underlying layer visible trough the apertured topsheet, which is perfectly discrete in use when used on dark colored undergarment, without the need of using dark colored absorbent core per se. Indeed process flexibility and raw material supply is therewith facilitated and more cost effective. Advantageously such an absorbent article is able to mask any bodily fluid, especially menstrual fluid, discharged on it and retained on it in the absorbent core. In such execution the light colored core might extend or not to the periphery of the article and thus be visible on the lateral edges thereof underlying the dark colored topsheet and secondary layer. Although such executions where the absorbent core having a L hunter value of 65 or more (preferably white absorbent core) extends to the edges of the absorbent article and is thus visible on the lateral edges of the absorbent article are not the preferred ones for complete discretion, the light absorbent core visible on the lateral edges of the article might serve as a visual indicator of bodily fluid loading and hence as an indicator of when to change such a dark colored absorbent article. In other executions the light colored absorbent core (e.g., white one) does not extend to the periphery of the article, and thus is neither visible trough the apertured topsheet, nor at the edges of the articles for perfect discretion in use with dark colored undergarments.
Highly preferred underlying layer is a nonwoven secondary layer. The nonwoven secondary layer prevents ‘bunching’, that is twisting of pantiliner/pad per se, or of the absorbent core in the crotch portion. The inner layer of the apertured topsheet is preferably secured in contacting relation with the nonwoven secondary layer. This contacting relationship results in liquid penetrating the apertured topsheet, preferably the formed film, faster than if the apertured topsheet was not in contact with the secondary layer.
The material of the nonwoven secondary layer can be the same as the nonwoven topsheet described herein before.
In another embodiment the underlying layer is provided by at least a portion of the absorbent core. This typically refers to absorbent articles without any layer between the topsheet and the absorbent core, i.e., the topsheet is directly adjacent to the absorbent core. In one execution the absorbent core extends to the periphery of the topsheet, thereby underlying the topsheet upon its entire surface. In other executions the absorbent core does not extend to the periphery of the topsheet. In such later executions the entire absorbent core provides a part of the underlying layer. In such executions the topsheet and the backsheet are joined to each other in the region extending beyond the periphery of the absorbent core.
In such an execution wherein the absorbent core does not underlie the entire surface of the topsheet, the backsheet or any intermediate layer (if present) between the absorbent core and the backsheet might provide the underlying layer in the region extending beyond the periphery of the absorbent core. Accordingly in such an execution the backsheet and/or any intermediate layer meets the requirement of the underlying layer as defined herein. Thus in some embodiments the underlying layer is provided by at least a portion of the backsheet and/or by at least a portion of an intermediate layer positioned between the absorbent core and the backsheet. Such an intermediate layer might be made by any of the material known to those skilled in the art (e.g., nonwoven, woven and the like).
Absorbent Core
Conventionally the absorbent core can be a single entity or comprise several layers. It can includes the following components: (a) optionally a primary fluid distribution layer; (b) optionally a secondary fluid distribution layer; (c) a fluid storage layer; (d) optionally a fibrous layer underlying the storage layer; and (e) other optional components.
a. Optional Primary Fluid Distribution Layer
One optional component of the absorbent core according to the present invention is the primary fluid distribution layer. This primary distribution layer typically underlies the topsheet (if present) and is in fluid communication therewith. The primary distribution layer acquires body fluid for ultimate distribution to the storage layer. This transfer of fluid through the primary distribution layer occurs mainly in the thickness, but may also provide distribution along the longitudinal and transverse directions of the article.
b. Optional Secondary Fluid Distribution Layer
Also optional according to the present invention is a secondary fluid distribution layer. This secondary distribution layer typically underlies the primary distribution layer and is in fluid communication therewith. The purpose of this secondary distribution layer is to readily acquire bodily fluid from the primary distribution layer and distribute it along the longitudinal and transverse directions of the article before transfer to the underlying storage layer. This helps the fluid capacity of the underlying storage layer to be fully utilized.
c. Fluid Storage Layer
Positioned in fluid communication with, and typically underlying the primary or secondary distribution layers, is a fluid storage layer.
The fluid storage layer may be any absorbent means that is capable of absorbing or retaining liquids (e.g., menses and/or urine). The fluid storage layer may be manufactured in a wide variety of sizes and shapes (e.g., rectangular, oval, hourglass, asymmetric, etc.) and from a wide variety of liquid-absorbent materials commonly used in sanitary napkins and other absorbent articles such as comminuted wood pulp that is generally referred to as airfelt. Examples of other suitable absorbent materials include creped cellulose wadding, modified cross-linked cellulose fibres (such as those described in U.S. Pat. No. 5,217,445 issued to Young, et al. on Jun. 8, 1993), capillary channel fibres (that is, fibres having intra-fibre capillary channels such as those described in U.S. Pat. No. 5,200,248 issued to Thompson, et al. on Apr. 6, 1993), absorbent foams (such as those described in U.S. Pat. No. 5,260,345, issued to DesMarais, et al. on Nov. 9, 1993 and U.S. Pat. No. 5,268,244 issued to DesMarais, et al. on Dec. 7, 1993), thermally bonded airlaid materials (such as those material described in U.S. patent application Ser. No. 08/141,156, entitled “Catamenial Absorbent Structures Having Thermally Bonded Layers For Improved Handling of Menstrual Fluids and Their Use In Catamenial Pads Having Improved Fit and Comfort” filed in the name of Richards, et al. on Oct. 21, 1993), absorbent sponges, synthetic staple fibres, polymeric fibres, hydrogel-forming polymer gelling agents, peat moss, tissue including tissue wraps and tissue laminates, or any equivalent materials or combinations of materials. Suitable fluid storage layers comprising foams are described in European Applications 0 598 833, 0 598 823 and 0 598 834. Suitable fluid storage layers comprising tissue laminates with particles of superabsorbent or gelling agents comprised therebetween are described in International Patent Applications WO 94/01069 and WO 95/17868.
Preferably the fluid storage layer comprises super-absorbent or gelling materials usually referred to as “hydrogels,” “superabsorbent”, “hydrocolloid” materials. Absorbent gelling materials are those materials that, upon contact with aqueous fluids, especially body fluids, imbibe such fluids and thus form hydrogels. These absorbent gelling materials are typically capable of absorbing large quantities of aqueous body fluids, and are further capable of retaining such absorbed fluids under moderate pressures. These absorbent gelling materials are typically in a granular form of discrete, non-fibrous particles. However, according to the present invention these super-absorbent gelling materials can also be provided in non-granular form too, preferably in a fibrous form.
In the fluid storage layer these absorbent gelling materials can be dispersed homogeneously or non-homogeneously in a suitable fibrous matrix also referred to as carrier. Suitable carriers include cellulose fibers, in the form of fluff, such as is conventionally utilized in absorbent cores. Modified cellulose fibers such as the stiffened cellulose fibers can also be used. Synthetic fibers can also be used and include those made of cellulose acetate, polyvinyl fluoride, polyvinylidene chloride, acrylics (such as Orion), polyvinyl acetate, non-soluble polyvinyl alcohol, polyethylene, polypropylene, polyamides (such as nylon), polyesters, bicomponent fibers, tricomponent fibers, mixtures thereof and the like. Preferred synthetic and man-made fibers have a denier of from about 3 denier per filament to about 25 denier per filament, more preferably from about 5 denier per filament to about 16 denier per filament. Also preferably, the fiber surfaces are hydrophilic or are treated to be hydrophilic. The storage layer can also include filler materials, such as Perlite, diatomaceous earth, Vermiculite, etc., that lower rewet problems. Further the storage layer may comprise a binder including but not limited to Latex binders which can be sprayed as an aqueous solution onto the surface of the storage layer prior to curing.
If the absorbent gelling materials are dispersed non-homogeneously in a fibrous matrix, the storage layer can be locally homogeneous, i.e. have a distribution gradient in one or several directions within the dimensions of the storage layer. Non-homogeneous distribution thus includes e.g. laminates of the fibrous carriers enclosing the absorbent gelling materials.
Preferably, the storage layer comprises from 5% to 95% absorbent gelling materials, preferably from 5% to 50%, most preferably from 8% to 35%, absorbent gelling materials. Further the storage layer can comprise from 5% to 95% carrier fibers, preferably from 95% to 50%, most preferably from 92% to 65% carrier fibers.
Suitable absorbent gelling materials for use herein will most often comprise a substantially water-insoluble, slightly crosslinked, partially neutralized, polymeric gelling material. This material forms a hydrogel upon contact with water. Such polymer materials can be prepared from polymerizable, unsaturated, acid-containing monomers. Suitable unsaturated acidic monomers for use in preparing the polymeric absorbent gelling material used in this invention include those listed in U.S. Pat. No. 4,654,039 (Brandt et al), issued Mar. 31, 1987, and reissued as RE No. 32,649 on Apr. 19, 1988. Preferred monomers include acrylic acid, methacrylic acid, and 2-acrylamido-2-methyl propane sulfonic acid.
Whatever the nature of the basic polymer components of the hydrogel-forming polymeric absorbent gelling materials, such materials will in general be slightly crosslinked. Crosslinking serves to render the hydrogel-forming polymer gelling materials substantially water-insoluble, and cross-linking thus in part determines the gel volume and extractable polymer characteristics of the hydrogels formed from these polymeric gelling materials. Suitable crosslinking agents are well known in the art and include, for example, those described in greater detail in U.S. Pat. No. 4,076,663 (Masuda et al), issued Feb. 28, 1978. Preferred crosslinking agents are the di- or polyesters of unsaturated mono- or polycarboxylic acids with polyols, the bisacrylamides and the di- or triallyl amines. Other preferred crosslinking agents are N,N′-methylenebisacrylamide, trimethylol propane triacrylate and triallyl amine. The crosslinking agent can generally constitute from about 0.001 mole percent to 5 mole percent of the resulting hydrogel-forming polymer material. More preferably, the crosslinking agent will constitute from about 0.01 mole percent to 3 mole percent of the hydrogel-forming polymeric gelling material.
The slightly crosslinked, hydrogel-forming polymeric gelling materials are generally employed in their partially neutralized form. For purposes of the present invention, such materials are considered partially neutralized when at least 25 mole per-cent, and preferably at least 50 mole percent of monomers used to form the polymer are acid group-containing monomers that have been neutralized with a salt-forming cation. Suitable salt-forming cations include alkali metal, ammonium, substituted ammonium and amines. This percentage of the total monomers utilized which are neutralized acid group-containing monomers is referred to herein as the “degree of neutralization.”
While these absorbent gelling materials have typically been disclosed in the prior art in granular form, it is possible too in the context of the present invention that the absorbent gelling material is in a non-granular form for example as macrostructures such as fibers, sheets or strips. These macrostructures can be prepared by forming the particulate absorbent gelling material into an aggregate, treating the aggregated material with a suitable crosslinking agent, compacting the treated aggregate to densify it and form a coherent mass, and then curing the compacted aggregate to cause the crosslinking agent to react with the particulate absorbent gelling material to form a composite, porous absorbent macrostructure. Such porous, absorbent macrostructures are disclosed, for example, in U.S. Pat. No. 5,102,597 (Roe et al), issued Apr. 7, 1992.
According to a particularly preferred embodiment of the present invention the absorbent core comprises only one layer, preferably one fluid storage layer.
Any method known to those skilled in the art for coloring materials might be used too for coloring absorbent core, including pigmenting the material, dying the material and/or color printing the material.
d. Optional Fibrous Layer
An optional component for inclusion in the absorbent cores according to the present invention is a fibrous layer adjacent to, and typically underlying the storage layer. This underlying fibrous layer would typically provide the same function as the secondary fluid distribution layer.
e. Other Optional Components
The absorbent cores according to the present invention can include other optional components normally present in absorbent webs. For example, a reinforcing scrim can be positioned within the respective layers, or between the respective layers, of the absorbent cores. Such reinforcing scrims should be of such configuration as to not form interfacial barriers to fluid transfer, especially if positioned between the respective layers of the absorbent core. Given the structural integrity that usually occurs as a result of thermal bonding, reinforcing scrims are usually not required for the absorbent structures according to the present invention.
Another component which can be included in the absorbent core according to the invention and preferably is provided close to or as part of the primary or secondary fluid distribution layer are odor control agents. Typically active carbon alone or coated with or in addition to other odor control agents, in particular suitable, zeolite, silica or clay materials, are optionally incorporated in the absorbent core.
Active carbon is the preferred odor control agent for use in the dark colored absorbent articles according to the present invention like black one, as this material provides outstanding odor control properties at low cost.
Physical Characteristics of Absorbent Cores
Absorbent cores are usually non extensible and non-elastic, however, they can be rendered extensible and depending on the selected materials can also be made to have elastic characteristics. The term “extensible” as used hereinafter refers to a structure which under external forces such as those occurring during use extends in the direction of the forces or in the direction of a component of the forces in cases where only mono directional extensibility is provided.
The term “elastic” as used hereinafter refers to extensible structures which return at least partially to their initial state after the forces causing the extension cease to be exerted. Absorbent cores can be corrugated or pleated in one or several directions to provide a certain extensibility while selection of elastic fibers for the structure can provide elasticity.
The absorbent cores should preferably be thin. A thickness of less than mm, preferably less than 3 mm, more preferably less than 1.8 mm, and even more preferable between 0.1 and 1.8 mm is desirable such that the resulting articles can also have a low thickness.
Absorbent Article Design
The dark colored materials as indicated above can be used beneficially in the context of sanitary napkins, panty liners and sweat pads (underarm or collar). A new product design, which is a sub-form of a sanitary napkin or panty liner form, namely thong shaped sanitary napkins or panty liners, so called thong liners, are particularly susceptible to the present invention. The thong liner design is such that it provides the sanitary napkin or panty liner with a shape such that it can be worn in thong slips, G-string undergarments or string panties, hence the thong shape is fundamentally triangular or trapezoidal.
Optional Components of the Absorbent Articles
Optionally, the absorbent articles of the present invention can comprise all those components typical for the intended product use. For example absorbent articles can comprise components such as wings in order to improve their positioning and soiling protection performance especially towards the rear end of the article. Such designs are shown for example in EP 130 848 or EP 134 086, Thong liners with wings are shown in U.S. design No. 394,503, UK designs 2,076,491 and 2,087,071 as well as internationally filed industrial model DM 045544, filed under the Hague Agreement, registered on Oct. 21, 1998.
If present the wings preferably match the color of the remaining article. In fact an article design in which the wings are matching the L Hunter value and preferably color of the remaining article is preferred. The reason is that wings when folded onto the external side of an undergarment are rather easily visible.
Irrespective whether the wings are specially designed for thong liners or for conventional absorbent articles they can be provided as separate pieces and be attached to the thong liner or conventional pantiliners or sanitary napkins, or they can be integral with the materials of the absorbent articles, e.g. by being integral extension of the topsheet, the backsheet or a combination thereof. If the wings are attached then they can be attached in a basic outward pointing position or already be predisposed towards their in-use position, i.e. towards the longitudinal centerline. If the wings are integral extensions of the topsheet or the backsheet or both then they are provided with the same L Hunter value and preferably color as these materials.
In general, all typically used components in absorbent products can also be comprised in the absorbent articles according to the present invention as long as the absorbent articles meet the L Hunter value criteria as set in the claims.
Most preferred absorbent articles will comprise a fastening adhesive for attachment. In the case of sanitary napkins, pantliners or thongliners a so-called panty fastening adhesive is preferred to be present on the backsheet for attachment to an undergarment. However, for sweat pads, e.g. underarm sweat pads, either attachment to an adjacent garment or attachment to the skin of the wearer directly can also be considered. Of course, such direct skin attachment, which is conventionally provided by water gel, hydrogel or oil gel based body adhesives, can also be used in sanitary napkins or body liners (in contrast to pantiliners).
EXAMPLES
Examples of pantiliners according to the present invention are as following:
Option 1
The pantiliner (as illustrated in FIG. 2) comprises:

    
    
        as the topsheet, a black apertured polyethylene formed film 3 having holes of 0.2 square millimeters and holes of 1.6 square millimeters, the open area of the apertured formed film being about 32% (black CPM DH®, code name 45105/99 available from BP Chemicals, Germany),
        as the underlying layer, a secondary layer 4 made of black nonwoven spunbonded polyethylene extending on the entire surface of the topsheet (code T27CXC commercially available from BBA, Linotec),
        a spiral layer of adhesive (H2128®, available from Ato Findley) (not shown),
        a white absorbent tissue core 5 with 10% super absorbent fibers (code GH.100.1004, basis weight 100 gsm commercially available from Concert GmbH, Falkenhagen-Germany),
        a spiral layer of adhesive (PM17®, available from Savare) (not shown),
        as the backsheet, a polyethylene micro embossed film 6 with black pigments type ST 700, commercially available from Britton Taco Ltd. Winsford Chesire UK
        stripes of panty fastening adhesive (HL1461, available from Fuller, Luneburg-Germany)) (not shown) and release paper 7.
    
    


Option 2
The pantiliner (as illustrated in FIG. 3) comprises:

    
    
        as a topsheet, a black apertured polyethylene formed film 3 having holes of 0.2 square millimeters and holes of 1.6 square millimeters, the open area of the apertured formed film being about 32% (black CPM DH®, code name 45105/99 available from BP Chemicals, Germany), together with black nonwoven spunbonded polyethylene outer layer 2 (code name T27CXC commercially available from BBA, Linotec),
        as the underlying layer, a secondary layer 4 made of black nonwoven spunbonded polyethylene extending on the entire surface of the apertured polyethylene formed film layer 3 (code T27CXC commercially available from BBA, Linotec),
        a spiral layer of adhesive (H2128®, available from Ato Findley) (not shown in FIG. 3),
        a white absorbent tissue core 5 with 10% super absorbent fibers (code GH.100.1004, basis weight 100 gsm commercially available from Concert GmbH, Falkenhagen-Germany),
        a spiral layer of adhesive (PM17®, available from Savare) (not shown in FIG. 3),
        as the backsheet, a polyethylene micro embossed film 6 with black pigments type ST 700, commercially available from Britton Taco Ltd. Winsford Chesire UK,
        stripes of panty fastening adhesive (HL1461, available from Fuller, Luneburg-Germany) (not shown in FIG. 3), and release paper 7.
    
    


Option 3

    
    
        The pantiliner (as illustrated in FIG. 4) comprises:
        as a topsheet, a black apertured polyethylene formed film 3 having holes of 0.2 square millimeters and holes of 1.6 square millimeters, the open area of the apertured formed film being about 32% (black CPM DH®, code name 45105/99 available from BP Chemicals, Germany), together with black nonwoven spunbonded polyethylene outer layer 2 (code name T27CXC commercially available from BBA, Linotec),
        the underlying layer is partly provided by a black absorbent tissue core 5 with 10% super absorbent fibers positioned in the center of the article and not extending to the periphery of the topsheet and in the region extending beyond the periphery of the absorbent core, the underlying layer is provided by the portion of the backsheet 6 (which extends beyond the periphery of the absorbent core to the periphery of the topsheet)
        a spiral layer of adhesive (PM17®, available from Savare) (not shown in FIG. 4),
        as the backsheet, a polyethylene micro embossed film 6 with black pigments type ST 700, commercially available from Britton Taco Ltd. Winsford Chesire UK,
        stripes of panty fastening adhesive (HL1461, available from Fuller, Luneburg-Germany) (not shown in FIG. 4), and release paper 7.
    
    


Option 4
The pantiliner (as illustrated in FIG. 2) comprises:

    
    
        as the topsheet, a black nonwoven spunbonded polyethylene 3 extending upon the entire surface of the pantiliner (code name T27CXC commercially available from BBA, Linotec)
        as the underlying layer, a secondary layer 4 made of black nonwoven spunbonded polyethylene extending on the entire surface of the topsheet (code T27CXC commercially available from BBA, Linotec),
        a spiral layer of adhesive (H2128®, available from Ato Findley) (not shown),
        a white absorbent tissue core 5 with 10% super absorbent fibers (code GH.100.1004, basis weight 100 gsm commercially available from Concert GmbH, Falkenhagen-Germany),
        a spiral layer of adhesive (PM17®, available from Savare) (not shown),
        as the backsheet, a polyethylene micro embossed film 6 with black pigments type ST 700, commercially available from Britton Taco Ltd. Winsford Chesire UK
        stripes of panty fastening adhesive (HL1461, available from Fuller, Luneburg-Germany)) (not shown) and release paper 7.
    
    


Option 5
The thong pantiliner 10 (as illustrated in FIG. 5 or 6) comprises:

    
    
        as a topsheet a black nonwoven spunbonded polyethylene extending upon the entire surface of the pantiliner (code name T27CXC commercially available from BBA, Linotec)
        spiral layer of adhesive (code name H2128 available form Ato-Findley)
        as the underlying layer, a full shape one side (top) black colored absorbing tissue core (110 gsm) made of cellulose fibers and synthetic fibers (bico PE/PP) commercially available from Duni, extending upon the entire surface of the topsheet
        a spiral layer of adhesive (PM17® available from Savare')
        as the backsheet, a polyethylene micro embossed film with black pigments type ST 700, commercially available from Britton Taco Ltd. Winsford Chesire UK,
        stripes of panty fastening adhesive (HL1461, available from Fuller, Luneburg-Germany) and release paper.
    
    


For all the pantiliners exemplified herein before the topsheet, underlying layer and backsheet have all an L Hunter value of less than 30.

## Claims

1. An absorbent article comprising an apertured topsheet, an underlying layer visible through the apertures of the topsheet and a backsheet, wherein the topsheet and the underlying layer independently have a L Hunter value of less than about 60.

2. The absorbent article according to claim 1, wherein the topsheet and the underlying layer independently have a L Hunter value of less than about 30.

3. The absorbent article according to claim 1, wherein the difference of L Hunter value ΔL between the underlying layer and the topsheet is less than about 20.

4. The absorbent article according to claim 1, wherein the L Hunter value of the underlying layer is equal or less than the L Hunter value of the topsheet.

5. The absorbent article according to claim 1, wherein the difference in color value ΔE between the topsheet and the underlying layer is less than about 40.

6. The absorbent article according to claim 1, wherein the topsheet and the underlying layer have the same color.

7. The absorbent article according to claim 1 wherein the topsheet comprises apertures having a pore size of 0.0001 mm to 5 mm.

8. The absorbent article according to claim 7, wherein the topsheet is a nonwoven and/or an apertured polymeric film.

9. The absorbent article according to claim 1 wherein the backsheet has a L Hunter value of less than about 60.

10. The absorbent article according to claim 9, wherein the backsheet has the same color as the topsheet.

11. The absorbent article according to claim 1, wherein the underlying layer is provided by at least a portion of a secondary layer.

12. The absorbent article according to claim 1, wherein the underlying layer is provided by at least a portion of an absorbent core.

13. The absorbent article according to claim 1 wherein the underlying layer is provided by at least a portion of the backsheet and/or at least a portion of an intermediate layer positioned between the absorbent core and the backsheet.

14. The absorbent article according to claim 12 wherein the underlying layer is provided by the absorbent core and by the backsheet extending beyond a periphery of said absorbent core.

15. The absorbent article according to claim 1, wherein said article is a sanitary napkin or a pantiliner.