# Patent

## Title
Absorbent article having stain resistant properties

## Abstract

A sanitary napkin including a body facing surface, a portion adapted to be arranged over the vaginal opening during use, a first colored portion, said colored portion extending over at least the portion of the napkin to be placed over the vaginal opening during use, a noncolored portion, wherein said first colored portion has a first color as measured from said body facing surface prior to staining, wherein the first colored portion has a second color as measured from said body facing surface after staining, wherein the first color has an average L value greater than 80; and wherein a Δa* between said first color and said second color is less than 18.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority to Application No. 60/772,684 filed on Feb. 13, 2006, the entire contents of which are incorporated by reference herein.


FIELD OF THE INVENTION
The present invention generally relates to absorbent articles such as a feminine sanitary napkins. More particularly, the present invention relates to a sanitary napkin having improved stain resistant properties.
BACKGROUND OF THE INVENTION
Sanitary napkins intended to absorb menstrual fluid are well known in the art. Most sanitary napkins in use today include a liquid permeable cover layer, a liquid impermeable barrier layer, and an absorbent system arranged between the cover layer and the barrier layer. The absorbent system may comprise a single layer absorbent material or may comprise multiple layers.
A disadvantage of prior art articles of the type described above is that once menstrual fluid is absorbed into the article the red color of the menstrual fluid is visible from the top surface of the article. The observation of the red color of the menstrual fluid from the top surface of the article has been identified as being unsightly and undesirable by users.
In view of the above problem, attempts have been made in the prior art to “mask” the stain produced by menstrual fluid, that is to minimize the visibility of the menstrual fluid from the top surface of the article after the fluid has been absorbed into the article. Various article configurations have been disclosed in the prior art adapted to mask menstrual fluid, i.e. intended to prevent the menstrual fluid from being viewed
Although some prior art articles are effective at masking menstrual fluid, it has been discovered that such articles have certain shortcomings. For example, many of the prior art articles adapted to mask menstrual fluid disclosed in the prior art employ a dark colored layer that functions to hide the menstrual fluid from view. However, such dark layers are also visible form the top surface of the napkin and are perceived as undesirable since the dark color suggests that the napkin is not hygienic or clean.
It has been also been discovered that although users do not like the red appearance of menstrual fluid when visible form the top surface of a sanitary napkin they do not desire that the menstrual fluid be completely blocked or masked from view. In particular, it has been discovered that users desire that the menstrual fluid be visible from the top surface of the napkin since the presence of the menstrual fluid reassures the user that they are menstruating in a healthy manner.
In view of the foregoing, it is an object of the present invention to provide a sanitary napkin that permits menstrual fluid be visible from the top surface of the napkin while at the same time minimizing the red appearance of the menstrual fluid from the top surface of the napkin. In addition, it is another object of the present invention to provide a sanitary napkin having these properties that does not have a dark colored appearance from the body facing surface of the napkin prior to use.
SUMMARY OF THE INVENTION
In view of the foregoing objectives, the present invention provides a sanitary napkin including a body facing surface, a portion adapted to be arranged over the vaginal opening during use, a first colored portion, said colored portion extending over at least the portion of the napkin to be placed over the vaginal opening during use, a noncolored portion, wherein said first colored portion has a first color as measured from said body facing surface prior to staining, wherein the first colored portion has a second color as measured from said body facing surface after staining, wherein the first color has an average L value greater than 80; and wherein a Δa* between said first color and said second color is less than 18.



BRIEF DESCRIPTION OF THE FIGURES
FIG. 1a is a schematic view of a three-dimensional film for use in absorbent articles according the present invention;
FIG. 1b is a partially broken-away perspective view of the film shown in FIG. 1a taken along line 1B in FIG. 1a; 
FIG. 1c is an enlarged photomicrograph of the three-dimensional film schematically shown in FIG. 1a, showing a top surface thereof;
FIG. 1d is an enlarged photomicrograph of the three-dimensional film shown in FIG. 1c, showing a bottom surface thereof;
FIG. 1e is a schematic view of a three-dimensional film, according a second embodiment, for use in absorbent articles according to the present invention;
FIG. 1f is a partially broken away perspective view of the film shown in FIG. 1e taken along line “1f” in FIG. 1e; 
FIG. 1g is a photomicrograph of the top surface of the three-dimensional film schematically shown in FIG. 1e; 
FIG. 1h is a photomicrograph of the bottom surface of the three-dimensional film shown in FIG. 1g; 
FIG. 1i is an enlarged photomicrograph of a portion of the three-dimensional film shown in FIG. 1g, said portion corresponding to the portion of the film encircled by the circle “1f” in FIG. 1e; 
FIG. 1j is an photomicrograph of the portion of the three-dimensional film shown in FIG. 1i showing a bottom surface thereof;
FIG. 2 is a schematic illustration of one type of three dimensional topographical support member useful to make films useful in absorbent articles according to the present invention;
FIG. 3 is a schematic illustration of an apparatus for laser sculpting a workpiece to form a three dimensional topographical support member useful to make a film used in absorbent articles according to the present invention;
FIG. 4 is a schematic illustration of a computer control system for the apparatus of FIG. 3;
FIG. 5 is a graphical representation of a file to laser sculpt a workpiece to produce a three dimensional topographical support member for producing an apertured film shown in FIGS. 1a-1d; 
FIG. 5a is a graphical representation of the file shown in FIG. 5 showing an enlarged portion thereof;
FIG. 5b is a graphical representation of a file to laser sculpt a workpiece to produce a three dimensional topographical support member for producing the apertured film shown in FIGS. 1e-1j; 
FIG. 5c is an enlarged portion of the graphical representation of the file shown in FIG. 5b showing the portion of the file encircled by the circle 5c in FIG. 5b; 
FIG. 5d is an enlarged portion of the graphical representation of the file shown in 5b showing the portion of the file encircled by the circle 5d in FIG. 5b; 
FIG. 5e is an enlarged portion of the graphical representation shown in FIG. 5d showing the portion of the file encircled by the circle 5e in FIG. 5d; 
FIG. 6 is a photomicrograph of a workpiece after it was sculpted utilizing the file of FIG. 5;
FIG. 6a is a photomicrograph of a workpiece after it was sculpted using the file shown in FIGS. 5b-5e; 
FIG. 6b is a enlarged portion of the workpiece shown in FIG. 6a, said enlarged portion corresponding to the area encircled by the circle 6b in FIG. 6a; 
FIG. 7 is a view of a support member used to make a film according to the invention in place on a film-forming apparatus;
FIG. 8 is a schematic view of an apparatus for producing an apertured film according to the present invention;
FIG. 9 is a schematic view of the circled portion of FIG. 8;
FIG. 10 is a graphical representation of a file to drill a workpiece using raster scan drilling to produce a three dimensional topographical support member for producing an apertured film;
FIG. 11 is a top plan view of an absorbent article according to the present invention;
FIG. 12 is an exploded perspective view of the absorbent article shown in FIG. 10; and
FIG. 13 is a perspective view of a portion of the absorbent article shown in FIG. 10 with the layers thereof partially cut away to reveal the underlying structure.



DETAILED DESCRIPTION OF THE INVENTION
The present invention is directed to an absorbent article, such as a feminine sanitary napkin, having improved stain resistant properties. More particularly the sanitary napkin according to the present invention minimizes the “red” appearance of the menstrual fluid after fluid is absorbed by the napkin while the napkin prior to staining has a light overall appearance.
Color measurements provided herein use the CIE La*b* color system. The La*b* color system, also known as the Hunter color scale, is well know to those skilled in the art. The La*b* system correlates to the sensitivity of the eye towards brightness or luminance and to color changes. The L value reflects the eye's sensitivity to brightness as one observes colors ranging from dark color to bright color and from gray to white. L is defined as 0 for a surface that is non-reflecting black and 100 for a surface that is non-fluorescing white. The variable a* represents the ratio of reflectance in the green region to reflectance in the red region and the variable b* represents the ratio of reflectance in the blue region to the yellow region of the electromagnetic spectrum.
The term “color” typically includes every value of the color space which includes black and white. However, for purposes of this application, when the term “color” or “colored” is used herein in describing the “colored portions” of the article it is intended to exclude black and white. As used herein, black is defined as L<25, −2<a*<2 and −2<b*<2. As used herein, white is defined as L>90, −2<a*<2 and −2<b<2. The terms “noncolored” and white are used interchangeably herein.
The L, a*, and b* values for the “colored” areas of the sanitary napkin 800, described in detail below, are the values as measured by a Minolta CR-321 color measurement system, using the 3 mm aperture, from the body-facing surface 801 of the napkin, unless otherwise specified.
Referring to FIG. 11, there is shown a first embodiment of the present invention, a sanitary napkin 800, showing the body-facing surface 801 thereof. The sanitary napkin 800 generally includes at least a first colored portion 802 and at least a noncolored portion 803. The colored portion 802 is arranged on the napkin so at least a portion of the colored portion 802 is located in the area of the napkin intended to be placed over the vaginal opening of the napkin during use. The napkin 800 includes an imaginary transverse center line “a” and an imaginary longitudinal center line “b”. In the embodiment of the napkin 800 shown in FIG. 11, the colored portion 802 extends along the longitudinally extending center line “b”. In addition, the colored portion 802 is symmetrical with respect to the longitudinal center line “b” and the transverse center line “a”.
The napkin 800 may optionally include a second colored portion 804. In the embodiment of the invention shown in FIG. 11, the second colored portion 804 consists of a substantially oval shaped colored ring 805 that is arranged to surround the first colored 802. The ring 805 is arranged in spaced relationship to the first colored portion 802 such that the ring 805 is separated from the first colored portion 802 by a noncolored area 806. The ring 805 preferably has a width “c” (See FIG. 12) of between 1 mm and 5 mm. Preferably, as shown in FIGS. 11-13, the ring 805 is “continuous”, i.e. the ring 805 is not interrupted by any noncolored portions but rather is a continuous colored band that entirely surrounds the first colored portion 802.
The first colored portion 802 preferably extends over about 15% to about 40% of the surface of the absorbent portion of the napkin 800 as viewed from the body facing surface 801 of the napkin. For purposes of the this invention “absorbent portion of the napkin” does not include the area of napkin defined by the wing areas 807. In the embodiment of the invention shown in FIG. 11, the terminal edge of the absorbent portion of the napkin is defined by the peripheral edge 847 of the transfer layer 846. The colored ring 805 preferably extends over about 3% to about 12% of the surface of the absorbent portion of the napkin 800 as viewed from the body facing surface of the napkin. Thus, the total colored portions of the napkin 800, e.g. including the first colored portion 802 and the second colored portion 804, extend over about 18% to about 52% of the absorbent portion of the napkin 800 as viewed from the body facing surface of the napkin.
The embodiment of the sanitary napkin 800 shown in FIGS. 12-13 includes a cover layer 842, a first absorbent layer 846, a second absorbent layer 848, a colored layer 849, and a barrier layer 850.
The colored layer 849 in one embodiment of the invention is an “internal layer” of the article, i.e. a layer located between the cover layer 842 and barrier layer 850. The colored layer 849 may be a separate layer from the absorbent layers 846 and 848 as shown in FIG. 12. For example, the colored layer 849 may comprise a tissue layer or the like arranged between the cover 842 and the transfer layer 846, the tissue layer having the colored portions preprinted thereon. Alternatively, the colored layer may comprise either the first absorbent layer 846 and/or the second absorbent layer 848. The colored layer may alternatively comprise the cover layer or the internal surface, i.e. non-garment facing surface of the barrier. The colored areas, e.g. 802 and 804, are preferably generated by applying a pigment or dye to the selected layer. The types of dyes and pigments suitable for use in the present invention, and their method of application, are well known to those of skill in the art.
Although the colored portions 802 and 804 described above may be a number of colors within the color spectrum it has been found that certain blue colors are particularly useful in the present invention. In particular, blue colors having L values between about 60 and about 85, a* between about −3.0 and −12.0, and b* between about −6.5 and about −15.0 are particularly useful in the present invention. These L, a* and b* values are as measured using as measured by a Minolta CR-321 color measurement system, using the 3 mm aperture, directly from the layer to which the color is applied.
When measured from the body facing surface of the article, the colored portions 802 and 804 preferably has an L value of between about 80 and about 92, an a* value of between about −6.0 and −3.5 and a b* value of between about −5.0 and about −10.0. More preferably, the colored portion has an L value of between about 85 and about 92, an a* value of between about −5.5 and about −4.0, and a b* value of between about −7.0 and −9.0.
Each of the cover layer 842, first absorbent layer 846, second absorbent layer, and barrier layer 850 layers is described in further detail below.
Cover Layer
The cover layer 842 is preferably an apertured film material and more preferably the cover layer 842 is an apertured film material of the type described in greater detail below with reference to FIGS. 1a-1j. A preferred apertured film cover layer for use in the present invention is commercially available on the Stayfree DryMax Ultrathin Napkin, distributed by the Personal Products Company division of McNeil-PPC, Inc., Skillman, N.J.
Reference is now made to FIGS. 1a-1d which depict an apertured film 10 according to one embodiment of the present invention. The film 10 includes a plurality of repeating interconnected frames 12. In the embodiment shown in FIGS. 1a-1d, each frame 12 includes opposed end regions 12a and 12b and opposed side walls 12c and 12d. Each of the end regions 12a and 12b being in spaced relationship to one another and each of the opposed side walls 12c and 12d being in spaced relationship to one another. In the specific embodiment shown in FIGS. 1a-1d, each of the frames 12 are interconnected to an adjacent frame 12. More particularly, as shown, each frame 12 “shares” a common side wall 12c, 12d, with a directly adjacent frame 12. Likewise, each frame 12 shares a common end region 12a, 12b with a directly adjacent frame 12. The apertured film 10 further includes first and second cross members 14a and 14b. As shown, cross member 14b extends from a first side wall 12c to an opposed side wall 12d of the frame 12. Likewise, cross member 14a extends from an end region 12a to the opposed end region 12b. In the embodiment of the invention shown in FIGS. 1a-1e, the cross members 14a and 14b intersect at the center of the frame is shown. In addition, in the embodiment of the invention shown in FIGS. 1a-1e, the cross members 14a and 14b are orthogonally arranged to one another.
Although the embodiment of the invention shown in FIGS. 1a-1d shows the apertured film 10 as having two cross members 14a and 14b, it is possible that only a single cross member could be employed as long as the cross member extends across the open area defined by the frame 12. Also, although the frame 12 has been shown as being generally hexagonal in shape, it is possible that other shapes could be used for the frame 12. Each of the cross members 14a and 14b preferably have a width “a” (See FIG. 1b) in the range of about 4.0 mils to about 24.0 mils (1 mil=0.001 inch). Each of the cross members 14a and 14b preferably have a length “b” (See FIG. 1b) in the range of about 30.0 mils to about 150.0 mils. The film 10 may optionally include a plurality of bumps 11 or the like arranged on the surface of the film as best seen in FIG. 1a. 
The film 10 further includes a plurality of apertures 16. Each aperture 16 is bound by at least a portion of the frame 12 and at least a portion of one of the cross members 14a and 14b. Reference is now made to FIG. 1b which is an illustration of a partially broken away perspective view of the film 10 shown in FIG. 1 taken along line 1B of FIG. 1a. Each aperture is bound by at least a portion of each of the cross members 14a and 14b as well as by a portion of the frame 12. More particularly, as best seen in FIG. 1b, each of the apertures 16 is bound by a corresponding interior wall 22, 24 of a respective side wall 12c, 12d of the frame portion 12. Each aperture 16 is further bound by a corresponding interior wall 26 or 28 of cross member 14b and a corresponding interior wall 30, 32 of cross member 14a. Finally, each aperture 16 is bound by a respective interior wall 34, 36 of a corresponding end region 12a, 12b. 
Again referring to FIG. 1b, film 10 generally includes a first generally planar top surface 18 in imaginary plane 23 and an opposed, generally planar, second bottom surface 21 in imaginary plane 25. The top surface 38 of the side walls 12c and 12d and the top surface 40 of the end regions 12a and 12b are coplanar with plane 23. However, the top surfaces 42 and 44 of cross members 14a and 14b are recessed relative to plane 23. More particularly, the top surfaces 42 and 44 of cross members 14a and 14b are located in a plane 27 located below both planes 23 and 25. Preferably the top surfaces 42 and 44 of the cross members 14a and 14b are recessed relative to the top surface 18 of the film, i.e. recessed relative to plane 23, to a depth in the range of about 3.0 mils to about 17.0 mils. The top surfaces 42 and 44 of cross members 14a and 14b are preferably substantially parallel to the imaginary planes 23 and 25.
The interior walls 22, 24 of side walls 12c and 12d, interior walls 26, 28 of cross member 14a, interior walls 30, 32 of cross member 14b, and interior walls 34, 36 of end regions 12a, 12b cooperate to define the apertures 16 and each of these interior walls extend below plane 25 such that the bottom opening of each aperture 16 is located below the bottom planar surface 21 of the film, i.e., below imaginary plane 25. More specifically, interior walls 22, 24 of side walls 12c and 12d, interior walls 26, 28 of cross member 14a, interior walls 30, 32 of cross member 14b, and interior walls 34, 36 of end regions 12a, 12b extend downwardly such that the bottom opening of each aperture is located in imaginary plane 29 which is located below imaginary planes 23, 25 and 27. It is noted that imaginary planes 23, 25, 27 and 29 are all substantially parallel to one another.
Since the top surfaces 42, 44 of the cross members 14a and 14b are recessed relative to the top surface 18 of the film 10, i.e. recessed relative to imaginary plane 23, a first relatively large aperture is effectively defined from the top surface 18 of the film 10 to the top surfaces 42, 44 of the cross members. The cross members 14a and 14b act to divide this larger aperture into four relatively smaller apertures which are in communication with the larger aperture from the top surfaces 42, 44 of the cross members 14a and 14b through the bottom opening of each aperture 16. Stated another way, within each frame member 12, a relatively large aperture is defined from plane 23 to plane 27 and a plurality of relatively smaller apertures, that are communication with the larger aperture, are defined from plane 27 to plane 29. In the embodiment shown in FIGS. 1a-1d, each of the smaller apertures defined from plane 27 to plane 29 have an area that is less than one quarter of the total area of the larger aperture defined from plane 23 to 27. In an embodiment in which a single cross member was employed, each of the smaller apertures defined by the cross member would have an area less than one half the total area of the larger aperture. The reader is advised that for simplicity and clarity in the drawings, both the “smaller” and “larger” apertures discussed above are generally identified by reference numeral 16 herein.
Reference is now made to FIGS. 1e-1j which depict an apertured film 100 according to a second embodiment of the present invention. The same or similar reference numbers are used in FIGS. 1e-1j as those used in FIGS. 1a-1d to identify the same and/or corresponding structure as identified in FIGS. 1a-1d and described above.
As best seen in FIGS. 1e and 1g, the film 100 includes at least a first portion 102 and at least a second portion 104. The first portion 102 is defined by a plurality of repeating interconnected frames 12 defining a plurality of apertures 16 as described above. In the embodiment shown in FIGS. 1e-1j, each frame 12 includes opposed end regions 12a and 12b and opposed side walls 12c and 12d. The apertured film 100 also includes first and second cross members 14a and 14b. The cross members 14a and 14b preferably have a width “a” in the range of about 4.0 mils to about 24.0 mils. Each of the cross members 14a and 14b preferably have a length “b” in the range of about 30.0 mils to about 150.0 mils. Preferably the top surfaces 42 and 44 of the cross members 14a and 14b are recessed relative to the top surface 18 of the film, i.e. recessed relative to plane 23, to a depth in the range of about 3.0 mils to about 17.0 mils.
Referring to FIG. 1f, the film 100 generally includes a substantially planar top surface 18 in imaginary plane 23 and an opposed, substantially planar, second bottom surface 21 in imaginary plane 25. The end regions 12a and 12b, and the portions 12c′ and 12d′ of the side walls 12c and 12d in the areas where the cross member 14b intersects with the side wall 12c and 12d, are formed such that at a least a portion of the top surface of the film in these areas is recessed relative to the imaginary plane 23. In the particular embodiment of the film 100 shown in FIG. 1f, the end regions 12a and 12b, and the portions 12c′ and 12d′ of the side walls 12c and 12d in the areas where the cross member 14b intersects with the side wall 12c and 12d, have a substantially “w” shape, or sinusoidal shape, cross section defining a pair of swales 111 and a peak 113 arranged between the swales 111. As shown, the top surface of the film 115 in the area of the swales 111 is located in a plane 35 which is recessed relative to the imaginary plane 23. In particular, plane 35 is located between plane 23 and plane 25. Preferably the swales 111, at their most recessed point relative to plane 23, have a depth in the range of about 2 to about 5 mils, relative to plane 23.
Although in the particular embodiment 100 the end regions 12a and 12b and the portions 12c′ and 12d′ of the side walls 12c and 12d in the areas where the cross member 14b intersects with the side wall 12c and 12d are formed to have a substantially “w” shaped cross section, these areas may be formed to have other shapes and configurations wherein at least a portion of the top surface of the film in the those areas where the cross members 14a and 14b intersect the frame 12 is recessed relative to plane 23. By forming the film 100 in those areas where the cross member 14a intersects the end regions 12a and 12 b, and in those areas where the cross member 14b intersects the side walls 12c and 12d, such that at least a portion thereof is recessed relative to plane 23 the perceived softness of the film is enhanced. Although in the specific embodiment of the invention shown in FIG. 1f the film 100 is formed in the end regions 12a and 12b, and in the portions 12c′ and 12d′ of the side walls 12c and 12d, such that at least a portion of the surface of the film is recessed relative to plane 23 it is possible to construct the film such that only one of these regions is recessed relative to plane 23. For example only portions 12c′ and 12d′ may be recessed or in the alternative only end regions 12a and 12b may be recessed.
As best seen in FIG. 1e, the second portion 104 of the apertured film 100a includes a second plurality of apertures 106 that are visually distinguishable from the first plurality of apertures 16. The term “visually distinguishable” as used herein means that each of the second plurality of apertures 106 has a shape and/or size that is sufficiently different from the shape and/or size of each of the apertures 16 of the first plurality of apertures 16 such that, when observed by the naked eye, each of the second plurality of apertures 106 is visually distinguishable from each of the first plurality of apertures 16. In one embodiment of the invention, shown in FIGS. 1e-1j each of the second plurality of apertures 106 has a generally elliptical shape with a major axis “y” and a minor axis “z”. Each of the major axis “y” and minor axis “z” preferably have a length in the range of about 5 mils to about 150 mils. In one specific embodiment, the major axis has a length of about 43 mils and the minor axis has a length of about 16 mils. In one preferred embodiment of the invention, each of the second plurality of apertures 106 are spaced from one another by a distance “n” of about 10 mils to about 100 mils when measured from the center of one aperture to the center of a horizontally adjacent aperture along a horizontal line, and each of the second plurality of apertures 106 are spaced from a vertically adjacent aperture 106 by a distance “o” of about 10 mils to about 70 mils when measured from the center of one aperture to the center of a vertically adjacent aperture along a diagonal connecting the center of each of the apertures. In a specific embodiment of the invention, the distance “n” is 40 mils and the distance “o” is 34 mils.
The second plurality of apertures 106 may be arranged in a pattern to define a design, indicia, text or the like, or combinations thereof. For example, in the embodiment of the invention shown in FIGS. 1e and 1g, the second plurality of apertures 106 are arranged to define a butterfly design. Although in the particular embodiment of the invention shown and described with reference to FIGS. 1e-1j, a butterfly design is depicted, any other number of designs are possible.
The film 100 shown in FIGS. 1e-1j is also provided with a border 108 that separates the first plurality of apertures 16 from the second plurality of apertures 106. Preferably, the border has a shape and size such that it is visually distinguishable, when viewed by the naked eye, from each of the first plurality of apertures 16 and each of the second plurality of apertures 106. Preferably the border 108 has a width “x” (See FIG. 1e) in the range of between about 25 mils and 90 mils. In one preferred embodiment of the invention the border 108 is not apertured. The surface of the film 109 located within the area defined by the border 108 is preferably recessed related to the top substantially planar surface 18 of the film. In other words, the surface of the film 109 bound within the border 108 is recessed relative to plane 23. Preferably the surface of the film 109 is recessed relative to plane 23 in an amount from about 2 mils to about 5 mils. The surface of the film defining the border 108 itself is preferably located within plane 23.
Preferably the border 108 cooperates with the second plurality of apertures 106 to visually define the design, indicia, text or the like. For example, in the embodiment of the film 100 shown, the border cooperates with the second plurality of apertures 106 to define a butterfly design.
Although a single butterfly is shown in FIG. 1e for simplicity a plurality of such elements may be spaced over the surface of the film. For example, in one specific embodiment the film may have a plurality of such butterflies spaced over the film material. In addition, different sized designs may be employed, for example in one specific embodiment a plurality of relatively large butterflies and a plurality of smaller butterflies are employed in the same film.
The apertured films according to the present invention preferably have an open area in the range about 20% to about 30%. Open area may be determined by using image analysis to measure the relative percentages of apertured and unapertured, or land, areas. Essentially image analysis converts an optical image from a light microscope into an electronic signal suitable for processing. An electronic beam scans the image, line-by-line. As each line is scanned, an output signal changes according to illumination. White areas produce a relatively high voltage and black areas a relatively low voltage. An image of the apertured formed film is produced and, in that image, the holes are white, while the solid areas of thermoplastic material are at various levels of gray.
The more dense the solid area, the darker the gray area produced. Each line of the image that is measured is divided into sampling points or pixels. The following equipment can be used to carry out the analysis described above: a Quantimet Q520 Image Analyzer (with v. 5.02B software and Grey Store Option), sold by LEICA/Cambridge Instruments Ltd., in conjunction with an Olympus SZH Microscope with a transmitted light base, a plan 1.0.times objective, and a 2.50 times eyepiece. The image can be produced with a DAGE MTI CCD72 video camera.
A representative piece of each material to be analyzed is placed on the microscope stage and sharply imaged on the video screen at a microscope zoom setting of 10 times. The open area is determined from field measurements of representative areas. The Quantimet program output reports mean value and standard deviation for each sample.
A suitable starting film for making a three-dimensional apertured film according to the present invention is a thin, continuous, uninterrupted film of thermoplastic polymeric material. This film may be vapor permeable or vapor impermeable; it may be embossed or unembossed; it may be corona-discharge treated on one or both of its major surfaces or it may be free of such corona-discharge treatment; it may be treated with a surface active agent after the film is formed by coating, spraying, or printing the surface active agent onto the film, or the surface active agent may be incorporated as a blend into the thermoplastic polymeric material before the film is formed. The film may comprise any thermoplastic polymeric material including, but not limited to, polyolefins, such as high density polyethylene, linear low density polyethylene, low density polyethylene, polypropylene; copolymers of olefins and vinyl monomers, such as copolymers of ethylene and vinyl acetate or vinyl chloride; polyamides; polyesters; polyvinyl alcohol and copolymers of olefins and acrylate monomers such as copolymers of ethylene and ethyl acrylate and ethylenemethacrylate. Films comprising mixtures of two or more of such polymeric materials may also be used. The machine direction (MD) and cross direction (CD) elongation of the starting film to be apertured should be at least 100% as determined according to ASTM Test No. D-882 as performed on an Instron test apparatus with a jaw speed of 50 inches/minute (127 cm/minute). The thickness of the starting film is preferably uniform and may range from about 0.5 to about 5 mils or about 0.0005 inch (0.0013 cm) to about 0.005 inch (0.076 cm). Coextruded films can be used, as can films that have been modified, e.g., by treatment with a surface active agent. The starting film can be made by any known technique, such as casting, extrusion, or blowing.
A method of aperturing the films according to the present invention involves placing the film onto the surface of a patterned support member. The film is subjected to a high fluid pressure differential as it is on the support member. The pressure differential of the fluid, which may be liquid or gaseous, causes the film to assume the surface pattern of the patterned support member. If the patterned support member has apertures therein, portions of the film overlying the apertures may be ruptured by the fluid pressure differential to create an apertured film. A method of forming an apertured film is described in detail in U.S. Pat. No. 5,827,597 to James et al., incorporated herein by reference.
Such a three dimensional apertured film is preferably formed by placing a thermoplastic film across the surface of an apertured support member with a pattern corresponding to desired final film shape. A stream of hot air is directed against the film to raise its temperature to cause it to be softened. A vacuum is then applied to the film to cause it to conform to the shape of the surface of the support member. Portions of the film lying over the apertures in the support member are further elongated until rupture to create apertures in the film.
A suitable apertured support member for making these three-dimensional apertured films is a three-dimensional topographical support member made by laser sculpting a workpiece. A schematic illustration of an exemplary workpiece that has been laser sculpted into a three dimensional topographical support member is shown in FIG. 2.
The workpiece 102 comprises a thin tubular cylinder 110. The workpiece 102 has non-processed surface areas 111 and a laser sculpted center portion 112. A preferred workpiece for producing the support member of this invention is a thin-walled seamless tube of acetal, which has been relieved of all residual internal stresses. The workpiece has a wall thickness of from 1-8 mm, more preferably from 2.5-6.5 mm. Exemplary workpieces for use in forming support members are one to six feet in diameter and have a length ranging from two to sixteen feet. However, these sizes are a matter of design choice. Other shapes and material compositions may be used for the workpiece, such as acrylics, urethanes, polyesters, high molecular weight polyethylene and other polymers that can be processed by a laser beam.
Referring now to FIG. 3, a schematic illustration of an apparatus for laser sculpting the support member is shown. A starting blank tubular workpiece 102 is mounted on an appropriate arbor, or mandrel 121 that fixes it in a cylindrical shape and allows rotation about its longitudinal axis in bearings 122. A rotational drive 123 is provided to rotate mandrel 121 at a controlled rate. Rotational pulse generator 124 is connected to and monitors rotation of mandrel 121 so that its precise radial position is known at all times.
Parallel to and mounted outside the swing of mandrel 121 is one or more guide ways 125 that allow carriage 126 to traverse the entire length of mandrel 121 while maintaining a constant clearance to the top surface 103 of workpiece 102. Carriage drive 133 moves the carriage along guide ways 125, while carriage pulse generator 134 notes the lateral position of the carriage with respect to workpiece 102. Mounted on the carriage is focusing stage 127. Focusing stage 127 is mounted in focus guide ways 128. Focusing stage 127 allows motion orthogonal to that of carriage 126 and provides a means of focusing lens 129 relative to top surface 103. Focus drive 132 is provided to position the focusing stage 127 and provide the focusing of lens 129.
Secured to focusing stage 127 is the lens 129, which is secured in nozzle 130. Nozzle 130 has means 131 for introducing a pressurized gas into nozzle 130 for cooling and maintaining cleanliness of lens 129. A preferred nozzle 130 for this purpose is described in U.S. Pat. No. 5,756,962 to James et al. which is incorporated herein by reference.
Also mounted on the carriage 126 is final bending mirror 135, which directs the laser beam 136 to the focusing lens 129. Remotely located is the laser 137, with optional beam bending mirror 138, to direct the beam to final beam bending mirror 135. While it would be possible to mount the laser 137 directly on carriage 126 and eliminate the beam bending mirrors, space limitations and utility connections to the laser make remote mounting far preferable.
When the laser 137 is powered, the beam 136 emitted is reflected by first beam bending mirror 138, then by final beam bending mirror 135, which directs it to lens 129. The path of laser beam 136 is configured such that, if lens 129 were removed, the beam would pass through the longitudinal center line of mandrel 121. With lens 129 in position, the beam may be focused above, below, at, or near top surface 103.
While this apparatus could be used with a variety of lasers, the preferred laser is a fast flow CO2 laser, capable of producing a beam rated at up to 2500 watts. However, slow flow CO2 lasers rated at 50 watts could also be used.
FIG. 4 is a schematic illustration of the control system of the laser sculpting apparatus of FIG. 3. During operation of the laser sculpting apparatus, control variables for focal position, rotational speed, and traverse speed are sent from a main computer 142 through connection 144 to a drive computer 140. The drive computer 140 controls focus position through focusing stage drive 132. Drive computer 140 controls the rotational speed of the workpiece 102 through rotational drive 123 and rotational pulse generator 124. Drive computer 140 controls the traverse speed of the carriage 126 through carriage drive 133 and carriage pulse generator 134. Drive computer 140 also reports drive status and possible errors to the main computer 142. This system provides positive position control and in effect divides the surface of the workpiece 102 into small areas called pixels, where each pixel consists of a fixed number of pulses of the rotational drive and a fixed number of pulses of the traverse drive. The main computer 142 also controls laser 137 through connection 143.
A laser sculpted three dimensional topographical support member may be made by several methods. One method of producing such a support member is by a combination of laser drilling and laser milling of the surface of a workpiece.
Methods of laser drilling a workpiece include percussion drilling, fire-on-the-fly drilling, and raster scan drilling.
A preferred method is raster scan drilling. In this approach, the pattern is reduced to a rectangular repeat element 141, an example of which is depicted in FIG. 11. This repeat element contains all of the information required to produce the desired pattern. When used like a tile and placed both end-to-end and side-by-side, the larger desired pattern is the result.
The repeat element 141 is further divided into a grid of smaller rectangular units or “pixels” 142. Though typically square, for some purposes, it may be more convenient to employ pixels of unequal proportions. The pixels themselves are dimensionless and the actual dimensions of the image are set during processing, that is, the width 145 of a pixel and the length 146 of a pixel are only set during the actual drilling operation. During drilling, the length of a pixel is set to a dimension that corresponds to a selected number of pulses from the carriage pulse generator 134. Similarly, the width of a pixel is set to a dimension that corresponds to the number of pulses from the rotational pulse generator 124. Thus, for ease of explanation, the pixels are shown to be square in FIG. 5a; however, it is not required that pixels be square, but only that they be rectangular.
Each column of pixels represents one pass of the workpiece past the focal position of the laser. This column is repeated as many times as is required to reach completely around workpiece 102. A white pixel represents an off instruction to the laser and each black pixel represents an on instruction to the laser. This results in a simple binary file of 1's and 0's where a 1, or white, is an instruction for the laser to shut off and a 0, or black, is an instruction for the laser to turn on.
Referring back to FIG. 4, the contents of an engraving file are sent in a binary form where 1 is off and 0 is on by the main computer 142 to the laser 137 via connection 143. By varying the time between each instruction, the duration of the instruction is adjusted to conform to the size of the pixel. After each column of the file is completed, that column is again processed, or repeated, until the entire circumference is completed. While the instructions of a column are being carried out, the traverse drive is moved slightly. The speed of traverse is set so that upon completion of a circumferential engraving, the traverse drive has moved the focusing lens the width of a column of pixels and the next column of pixels is processed. This continues until the end of the file is reached and the file is again repeated in the axial dimension until the total desired width is reached.
In this approach, each pass produces a number of narrow cuts in the material, rather than a large hole. Because these cuts are precisely registered to line up side-by-side and overlap somewhat, the cumulative effect is a hole.
A highly preferred method for making the laser sculpted three dimensional topographical support members is through laser modulation. Laser modulation is carried out by gradually varying the laser power on a pixel by pixel basis. In laser modulation, the simple on or off instructions of raster scan drilling are replaced by instructions that adjust on a gradual scale the laser power for each individual pixel of the laser modulation file. In this manner, a three dimensional structure can be imparted to the workpiece in a single pass over the workpiece.
Laser modulation has several advantages over other methods of producing a three dimensional topographical support member. Laser modulation produces a one-piece, seamless, support member without the pattern mismatches caused by the presence of a seam. With laser modulation, the support member is completed in a single operation instead of multiple operations, thus increasing efficiency and decreasing cost. Laser modulation eliminates problems with the registration of patterns, which can be a problem in a multi-step sequential operation. Laser modulation also allows for the creation of topographical features with complex geometries over a substantial distance. By varying the instructions to the laser, the depth and shape of a feature can be precisely controlled and features that continuously vary in cross section can be formed. Also, with laser sculpting the regular positions of the apertures relative to one another can be maintained.
Referring again to FIG. 4, during laser modulation the main computer 142 may send instructions to the laser 137 in other than a simple “on” or “off” format. For example, the simple binary file may be replaced with an 8 bit (byte) format, which allows for a variation in power emitted by the laser of 256 possible levels. Utilizing a byte format, the instruction “11111111” instructs the laser to turn off, “00000000” instructs the laser to emit full power, and an instruction such as “10000000” instructs the laser to emit one-half of the total available laser power.
A laser modulation file can be created in many ways. One such method is to construct the file graphically using a gray scale of a 256 color level computer image. In such a gray scale image, black can represent full power and white can represent no power with the varying levels of gray in between representing intermediate power levels. A number of computer graphics programs can be used to visualize or create such a laser-sculpting file. Utilizing such a file, the power emitted by the laser is modulated on a pixel by pixel basis and can therefore directly sculpt a three dimensional topographical support member. While an 8-bit byte format is described here, other levels, such as 4 bit, 16 bit, 24 bit or other formats can be substituted.
A suitable laser for use in a laser modulation system for laser sculpting is a fast flow CO2 laser with a power output of 2500 watts, although a laser of lower power output could be used. Of primary concern is that the laser must be able to switch power levels as quickly as possible. A preferred switching rate is at least 10 kHz and even more preferred is a rate of 20 kHz. The high power-switching rate is needed to be able to process as many pixels per second as possible.
FIG. 5 is a graphical representation of a laser modulation file, including a repeat element 141a, that may be used to form a support member for forming the apertured film shown in FIGS. 1a-1e. FIG. 5a is an enlarged portion of the laser modulation file shown in FIG. 5.
FIG. 5b is a graphical representation of a laser modulation file, including a repeat element 141b, that may be used to form a support member for forming the apertured film shown in FIGS. 1e-1j. FIG. 5c is an enlarged portion of the laser modulation file shown in FIG. 5b corresponding to the portion of file encircled by the circle “5c” in FIG. 5b. FIG. 5d is an enlarged portion of the laser modulation file shown in FIG. 5b corresponding to the portion of file encircled by the circle “5d” in FIG. 5b. FIG. 5e is an enlarged portion of the laser modulation file shown in FIG. 5b corresponding to the portion of file encircled by the circle “5e” in FIG. 5d. 
In FIGS. 5 through 5e the black areas 154a indicate pixels where the laser is instructed to emit full power, thereby creating a hole in the support member, which corresponds to apertures 16 in the three-dimensional apertured film 10 illustrated in FIGS. 1a-1d. The light gray areas 155 indicate pixels where the laser receives instructions to apply a very low level power, thereby leaving the surface of the support member essentially intact. These areas of the support member correspond to the protuberances 11 shown in FIG. 1a. The other areas depicted in FIGS. 5-5e, which are depicted in various levels of gray, represent corresponding levels of laser power and correspond to various features of the films 10 and 100 shown in FIGS. 1a-1d and FIGS. 1e-1j respectively. For example, areas 157 and 159 correspond to cross members 14a and 14b of the film 10 and the film 100.
FIG. 6 is a photomicropgraph of a portion 161 of a support member after it was engraved using the file shown in FIG. 5. The pattern on the portion of support member shown in FIG. 6 is repeated over the surface of the support member to thereby produce the repeating pattern of the film 10 shown in FIGS. 1a-1d. 
FIG. 6a is a photomicropgraph of a portion 162 of a support member after it was engraved using the file shown in FIG. 5. The pattern on the portion of support member shown in FIG. 6a is repeated over the surface of the support member to thereby produce a film having repeating butterfly pattern of the type shown in FIGS. 1e-1j. FIG. 6b is an enlarged portion of the support member shown in FIG. 6a corresponding to the portion of the support member in FIG. 6a encircled by the circle “6”b. Upon completion of the laser sculpting of the workpiece, it can be assembled into the structure shown in FIG. 7 for use as a support member. Two end bells 235 are fitted to the interior of the workpiece 236 with laser sculpted area 237. These end bells can be shrink-fit, press-fit, attached by mechanical means such as straps 238 and screws 239 as shown, or by other mechanical means. The end bells provide a method to keep the workpiece circular, to drive the finished assembly, and to fix the completed structure in the aperturing apparatus.
A preferred apparatus for producing such three dimensional apertured films is schematically depicted in FIG. 8. As shown here, the support member is a rotatable drum 753. In this particular apparatus, the drum rotates in a counterclockwise direction. Positioned outside drum 753 is a hot air nozzle 759 positioned to provide a curtain of hot air to impinge directly on the film supported by the laser sculpted support member. Means is provided to retract hot air nozzle 759 to avoid excessive heating of the film when it is stopped or moving at slow speed. Blower 757 and heater 758 cooperate to supply hot air to nozzle 759. Positioned inside the drum 753, directly opposite the nozzle 759, is vacuum head 760. Vacuum head 760 is radially adjustable and positioned so as to contact the interior surface of drum 753. A vacuum source 761 is provided to continuously exhaust vacuum head 760.
Cooling zone 762 is provided in the interior of and contacting the inner surface of drum 753. Cooling zone 762 is provided with cooling vacuum source 763. In cooling zone 762, cooling vacuum source 763 draws ambient air through the apertures made in the film to set the pattern created in the aperturing zone. Vacuum source 763 also provides means of holding the film in place in cooling zone 762 in drum 753 and provides means to isolate the film from the effects of tension produced by winding up the film after its aperturing.
Placed on top of laser sculpted support member 753 is a thin, continuous, uninterrupted film 751 of thermoplastic polymeric material.
An enlargement of the circled area of FIG. 8 is shown in FIG. 9. As shown in this embodiment, vacuum head 760 has two vacuum slots 764 and 765 extending across the width of the film. However, for some purposes, it may be preferred to use separate vacuum sources for each vacuum slot. As shown in FIG. 23, vacuum slot 764 provides a hold down zone for the starting film as it approaches air knife 758. Vacuum slot 764 is connected to a source of vacuum by a passageway 766. This anchors the incoming film 751 securely to drum 753 and provides isolation from the effects of tension in the incoming film induced by the unwinding of the film. It also flattens film 751 on the outer surface of drum 753. The second vacuum slot 765 defines the vacuum aperturing zone. Immediately between slots 764 and 765 is intermediate support bar 768. Vacuum head 760 is positioned such that the impingement point of hot air curtain 767 is directly above intermediate support bar 768. The hot air is provided at a sufficient temperature, a sufficient angle of incidence to the film, and at a sufficient distance from the film to cause the film to become softened and deformable by a force applied thereto. The geometry of the apparatus ensures that the film 751, when softened by hot air curtain 767, is isolated from tension effects by hold-down slot 764 and cooling zone 762 (FIG. 22). Vacuum aperturing zone 765 is immediately adjacent hot air curtain 767, which minimizes the time that the film is hot and prevents excessive heat transfer to support member 753.
Referring to FIGS. 8 and 9, a thin flexible film 751 is fed from a supply roll 750 over idler roll 752. Roll 752 may be attached to a load cell or other mechanism to control the feed tension of the incoming film 751. The film 751 is then placed in intimate contact with the support member 753. The film and support member then pass to vacuum zone 764. In vacuum zone 764 the differential pressure further forces the film into intimate contact with support member 753. The vacuum pressure then isolates the film from the supply tension. The film and support member combination then passes under hot air curtain 767. The hot air curtain heats the film and support member combination thus softening the film.
The heat-softened film and the support member combination then pass into vacuum zone 765 where the heated film is deformed by the differential pressure and assumes the topography of the support member. The heated film areas that are located over open areas in the support member are further deformed into the open areas of the support member. If the heat and deformation force are sufficient, the film over the open areas of the support member is ruptured to create apertures.
The still-hot apertured film and support member combination then passes to cooling zone 762. In the cooling zone a sufficient quantity of ambient air is pulled through the now-apertured film to cool both the film and the support member.
The cooled film is then removed from the support member around idler roll 754. Idler roll 754 may be attached to a load cell or other mechanism to control winding tension. The apertured film then passes to finish roll 756, where it is wound up.
Absorbent System—First Absorbent Layer
U.S. Pat. No. 6,515,195 discuses an absorbent system that may be employed in the absorbent article according, the subject matter of which is hereby incorporated by reference.
Adjacent to the cover layer 842 on its inner side and bonded to the cover layer 842 is a first absorbent layer 846 that forms part of the absorbent system. The first absorbent layer 846 provides the means of receiving body fluid from the cover layer 842 and holding it until an underlying second absorbent layer has an opportunity to absorb the fluid and therefore acts as a fluid transfer or acquisition layer.
The first absorbent layer 846 is, preferably, more dense than and has a larger proportion of smaller pores than the cover layer 842. These attributes allow the first absorbent layer 846 to contain body fluid and hold it away from the outer side of the cover layer 842, thereby preventing the fluid from rewetting the cover layer 842 and its surface. However, the first absorbent layer 846 is, preferably, not so dense as to prevent the passage of the fluid through the layer 846 into the underlying second absorbent layer 848.
The first absorbent layer 846 may be composed of fibrous materials such as wood pulp, polyester, rayon, flexible foam, or the like, or combinations thereof. The first absorbent layer 846 may also comprise thermoplastic fibers for the purpose of stabilizing the layer and maintaining its structural integrity. The first absorbent layer 846 may be treated with surfactant on one or both sides in order to increase its wettability, although generally the first absorbent layer 846 is relatively hydrophilic and may not require treatment. The first absorbent layer 846 is preferably bonded or adhered on both sides to the adjacent layers, i.e., the cover layer 842 and an underlying second absorbent layer 848.
Materials particularly suitable for use in the first absorbent layer 846 have a density in the range of about 0.04 to 0.05 g/cc, a basis weight in the range from about 80 to 110 g/m2(gsm), a thickness in the range of about 2 to 3 mm and in particular a thickness of 2.6 mm. Examples of suitable materials for the first absorbent layer are through air bonded pulp sold by Buckeye of Memphis, Tenn., under the designation VIZORB 3008, which has a basis weight of 110 gsm, VIZORB 3010, which has a basis weight of 90 gsm, VIZORB 3003, which has a basis weight of 100 gsm, and VIZORB 3042 which has a basis weight of 100 gsm.
Absorbent System—Second Absorbent Layer
Immediately adjacent to and bonded to the first absorbent layer 846 is the second absorbent layer 848. In one embodiment, the second absorbent layer 848 is a blend or mixture of cellulosic fibers and superabsorbent disposed in and amongst fibers of that pulp. In a specific example, the second absorbent layer 848 is a material containing from about 40 weight percent to about 95 weight percent cellulosic fibers and from about 5 weight percent to about 60 weight percent SAP (superabsorbent polymers). The material has a water content of less than about 10 weight percent. As used herein, the phrase “weight percent” means weight of substance per weight of final material. By way of example, 10 weight percent SAP means 10 gsm SAP per 100 gsm basis weight of the material.
Cellulosic fibers that can be used in the second absorbent layer 848 are well known in the art and include wood pulp, cotton, flax and peat moss. Wood pulp is preferred. Pulps can be obtained from mechanical or chemi-mechanical, sulfite, kraft, pulping reject materials, organic solvent pulps, etc. Both softwood and hardwood species are useful. Softwood pulps are preferred. It is not necessary to treat cellulosic fibers with chemical debonding agents, cross-linking agents and the like for use in the present material.
The second absorbent layer 848 can contain any superabsorbent polymer (SAP), which SAPs are well known in the art. For the purposes of the present invention, the term “superabsorbent polymer” (or “SAP”) refers to materials which are capable of absorbing and retaining at least about 10 times their weight in body fluids under a 0.5 psi pressure. The superabsorbent polymer particles of the invention may be inorganic or organic crosslinked hydrophilic polymers, such as polyvinyl alcohols, polyethylene oxides, crosslinked starches, guar gum, xanthan gum, and the like. The particles may be in the form of a powder, grains, granules, or fibers. Preferred superabsorbent polymer particles for use in the present invention are crosslinked polyacrylates, such as the product offered by Sumitomo Seika Chemicals Co., Ltd. Of Osaka, Japan, under the designation of SA60N Type II*, and the product offered by Chemical International, Inc. of Palatine, Ill., under the designation of 2100A*.
In a specific example, the second absorbent layer 848 is a material containing from about 40 to about 95 weight percent cellulosic fibers and, more specifically, from about 60 to about 80 weight percent cellulosic fibers. Such a material may contain from about 5 to about 60 weight percent SAP, preferably from about 20 to about 55 weight percent SAP, even more preferably from about 30 to about 45 weight percent SAP, and most preferably about 40 weight percent SAP.
In a preferred embodiment, the second absorbent layer 848 is manufactured by using air-laying means. The second absorbent layer 848 of the present invention is of high density and in a specific example has a density of greater than about 0.25 g/cc. Specifically, the second absorbent layer 848 may have a density in the range of from about 0.30 g/cc to about 0.50 g/cc. More specifically, the density is from about 0.30 g/cc to about 0.45 g/cc and, even more specifically, from about 0.30 g/cc to about 0.40 g/cc.
Air-laid absorbents are typically produced with a low density. To achieve higher density levels, such as the examples of the second absorbent layer 848 given above, the air-laid material is compacted using calendars. Compaction is accomplished using means well known in the art. Typically such compaction is carried out at a temperature of about 100 degrees C. and a load of about 130 Newtons per millimeter. The upper compaction roll is typically made of steel while the lower compaction roll is a flexroll having a hardness of about 85 SH D. It is preferred that both the upper and lower compaction rolls be smooth, although the upper roll can be engraved.
The second absorbent layer 848 can be prepared over a wide range of basis weights. The second absorbent layer 848 can have a basis weight in the range of from about 100 gsm to about 700 gsm. In a specific example, the basis weight ranges from about 150 gsm to about 400 gsm.
Preferably, the basis weight ranges from about 200 gsm to about 350 gsm and, more preferably, to about 300 gsm. The second absorbent layer 848 functions synergistically with the first absorbent layer to reduce the rewet potential. The first absorbent layer, having a relatively open pore structure, readily absorbs and disperses liquid laterally within its bulk and readily transfers the liquid to the receiving surface of the second absorbent layer. In turn, the second absorbent layer, having good capillarity efficiently draws liquid into its bulk from the first absorbent layer. Once the liquid has been absorbed into superabsorbent polymer, the liquid cannot be subsequently released by applying pressure. Therefore, the liquid absorbed into the superabsorbent material becomes permanently entrapped. At the same time, the strength with which the second absorbent layer intakes liquid from the first absorbent layer helps to reduce the proportion of liquid held in the first absorbent layer, thereby reducing the amount of liquid that returns to the cover layer when the napkin is subjected to mechanical loading. Furthermore, the first absorbent layer has a relatively high capillarity so that any concentration of liquid in the first absorbent layer resulting from mechanical loading can be redistributed within the material to lower concentrations, again reducing the amount of liquid which can return to the cover layer.
In a specific embodiment, the second absorbent layer contains in the range from about 30 to 40 weight percent superabsorbent material, has a basis weight in the range from about 200 to 400 gsm and a density in the range from about 0.2 to 0.45 g/cc. Even where prepared as from multiple layers, the final thickness of the formed second absorbent layer 848 is low. The thickness can vary from about 0.5 mm to about 2.5 mm. In a specific example, the thickness is from about 1.0 mm to about 2.0 mm and, even more specifically, from about 1.25 mm to about 1.75 mm.
For further details on the structure and the method of construction of the second absorbent layer 848, the reader is invited to refer to the U.S. Pat. No. 5,866,242 granted on Feb. 2, 1999 to Tan et al. The contents of this document are hereby incorporated by reference.
Barrier Layer
Underlying the absorbent system 848 is a barrier layer 850 comprising liquid-impervious material so as to prevent liquid that is entrapped in the absorbent system 848 from egressing the sanitary napkin and staining the wearer's undergarment. The barrier layer 850 is preferably made of polymeric film, although it may be made of liquid-impervious air-permeable material such as repellent-treated, non-woven or microporous films or foams.
The cover layer 842 and the barrier layer 850 are joined along their marginal portions so as to form an enclosure or flange seal that maintains the absorbent system 848 captive. The joint may be made by means of adhesives, heat-bonding, ultrasonic bonding, radio frequency sealing, mechanical crimping, and the like and combinations thereof.
Test Articles
Comparative Test Sample #1—Always Regular Ultrathin, commercially available from the Procter & Gamble, Co., Cincinnati, Ohio. The Always Regular Ultrathin product includes a substantially centrally arranged green colored area.
Comparative Test Sample #2—Always Regular Maxi, commercially available from the Procter & Gamble, Co., Cincinnati, Ohio. The Always Regular Maxi product includes a substantially centrally arranged blue colored area.
Inventive Test Sample #1—An article according the present invention was constructed as follows:
(1) Cover Layer—was constructed by first creating an apertured film as described above with reference to FIGS. 1e-1j, and described below. The upper surfaces of cross members 14a and 14b were recessed relative to the upper surface of film by 4.5 mils and the width of each cross member 14a and 14b was 5 mils and 9 mils respectively. The length of each of the cross members 14a and 14b was 100 mils and 60 mils respectively. The film included a plurality of larger butterfly patterns of the type shown in FIG. 1e and a plurality of smaller butterfly patterns of the type shown in FIG. 1e. The size of the larger butterfly was 1.0 inch when measured from the most distal point of one wing to the most distal point of the other wing, and 0.6 inch when measured at the most narrow waist portion of the butterfly. The size of the smaller butterfly was 0.6 inch when measured from the most distal point of one wing to the most distal point of the other wing, and 0.4 inch when measured at the most narrow waist portion of the butterfly. The larger and smaller butterflies were equally spaced such that a 9 inch (length)×6 inch (width) swatch of the apertured film had 9 large and 9 small butterflies equally spaced over the swatch of the film. Each of the large and small butterflies included a border 108 and a plurality of apertures 106 arranged within the area defined by the border. The border 108 of each of the larger butterflies had a width of 78 mils and the border 108 for each of the smaller butterflies had a width of 31 mils. The surface of the film within the area 109 of the film defined by the of the borders 108, for both the larger and smaller butterflies, was recessed relative to the top surface of the film by an amount of about 4.5 mils. The areas bound by border 109 of both the smaller and larger butterflies had a plurality of apertures 106, each of the apertures 106 having a elliptical shape with a major axis of 43 mils and a minor axis of 16 mils. The distance “n” between horizontally adjacent apertures 106 was 40 mils and the distance “o” between vertically adjacent apertures was 34 mils.
(2) Transfer Layer—100 gsm through air bonded pulp commercially available from Buckeye Technologies Incorporated, Memphis, Tenn., under product code VIZORB 3042. The transfer layer was printed on the top surface thereof, i.e. cover facing surface, with AcryjetTM fabric ink jet CV inks commercially available from Rohm & Haas Co., Philadelphia, Pa., under product codes RH-10246118 (Black), RH-10246119 (Cyan), RH-10246120 (Yellow), RH-10246171 (Magenta). The transfer layer was printed using a Mimaki Ink Jet Printer and the inks were applied so that the resultant pattern on the transfer layer corresponded to the colored portions 802 and 804 of the article shown in FIG. 1. The L, a* and b* values of colored portions of the transfer layer, as measured directly from the transfer layer, using a Minolta CR-321 color measurement system (SN209810050), using the 3 mm aperture, were L=81.01, a*=−4.87 and b*=−7.99. The transfer layer was constructed so that the total absorbent area of the napkin has an area of 15,300 mm2, the first colored portion had an area of 3,900 mm (26% of the total absorbent area), and the second colored portion had an area of 1,100 mm2 (7% of total absorbent area).
(3) A 225 gsm compressed pulp/superabsorbent core, commercially available from EAM Corporation, Jessup, Ga., under product code J2250525.
(4) A 20 gsm polyethylene film barrier commercially available from Pliant Corporation, Schaumburg, Ill., under product code XP-3492B.
Test Fluid
The test fluid used in the test method described below had the following composition:

    
    
        (1) 49.45% of 0.9% sodium chloride solution (VWR catalog # VW 3257-7);
        (2) 49.00% Glycerin (Emery 917);
        (3) 1% Phenoxyethanol (Clariant Corporation PhenoxetolTM);
        (4) 0.45% Sodium Chloride (Baker sodium chloride crystal #9624-05);
        (5) 0.11% FD&C #40 red dye (Waner Jenkinson, South Plainfield, N.J.).

The percentages provided above are percentages by weight.

Test Method for Measuring Color Change In Response to Staining Within Colored Portion of the Article

    
    


Five specimens of each of the comparative samples and inventive sample were tested according to the test method set forth below.
An apparatus capable of measuring L, a* and b* values is required to carry out test method, a Minolta CR-321 color measurement system, using the 3 mm aperture, was employed to determine the L, a* and b* values set forth herein.
Each of the specimens are removed from any packaging and the specimens are conditioned by leaving them in a room that is 21° C., +/−1° C. and 50%, +/−2.0%, relative humidity for a period of one hour.
A specimen for a particular product sample is placed upon a flat surface with the cover of the article facing up. L, a* and b* readings are taken of the article at a location intended to placed over the vaginal opening during use of the product. The aperture of the apparatus should be placed to it is arranged entirely within the colored area. The L, a* and b* values of the unstained or “clean” napkin are recorded.
A test plate having a centrally arranged elliptical orifice is placed on top of the cover of the product such that the center of the elliptical orifice is arranged over the portion of the article intended to be placed over the vaginal opening during use. The test plate consists of a 7.6 cm×25.4 cm plate of 1.3 cm thick polycarbonate with an elliptical orifice in its center. The elliptical orifice measures 3.8 cm along its major axis and 1.9 cm along its minor axis. A graduated 10 cc syringe containing 7 cc of test fluid is used to place the test fluid within the elliptical orifice. The test plate is removed once fluid has been absorbed and the cover is again visible.
After staining, the article should be permitted to equilibrate at room temperature for a period of five minutes. L, a* and b* measurements are taken over the stained portion article at the location intended to placed over the vaginal opening during use of the product.
The above described process is repeated for five product samples and the average L, a* and b* values for the clean article and stained article are calculated. After the average L, a* and b* values have been calculated for both the clean and stained article, the average change in L, i.e. ΔL, the average change in a*, i.e. Δa*, and the average change in b*, i.e. Δb*, are calculated. Tables are provided below setting forth the measured values for Comparative Test Sample #1, Comparative Test Sample #2, and Inventive Test Sample #1.







TABLE 1







Comparative Test Sample #1 - Colored Area, Pre-Staining












Specimen
L
a*
b*







#1
86.71
−5.97
0.13



#2
87.42
−5.79
0.09



#3
86.59
−6.04
0.22



#4
87.13
−6.11
0.27



#5
85.73
−6.49
0.60



Average
86.72
−6.08
0.26

















TABLE 2







Comparative Test Sample #1 - Colored Area, Post-Staining












Specimen
L
a*
b*







#1
67.99
13.85
0.84



#2
65.88
15.80
1.41



#3
67.43
14.44
0.86



#4
67.44
13.46
0.15



#5
66.83
13.59
0.45



Average
67.11
14.23
0.74

















TABLE 3







Comparative Test Sample #1 - Colored Area, Average ΔL, Δa*, Δb*









ΔL
Δa*
Δb*





19.61
20.31
1.00
















TABLE 4







Comparative Test Sample #2 - Colored Area, Pre-Staining












Specimen
L
a*
b*







#1
87.67
−5.76
−7.64



#2
87.39
−5.05
−7.25



#3
86.62
−5.32
−7.29



#4
87.55
−5.64
−7.49



#5
88.16
−5.26
−7.06



Average
87.48
−5.47
−7.35

















TABLE 5







Comparative Test Sample #2 - Colored Area, Post-Staining












Specimen
L
a*
b*
















#1
75.03
12.37
0.64



#2
74.08
13.37
1.40



#3
72.95
14.41
1.69



#4
71.99
15.52
2.34



#5
70.59
18.08
3.24



Average
72.93
14.75
1.86

















TABLE 6







Comparative Test Sample #2 - Colored Area, Average ΔL, Δa*, Δb*









ΔL
Δa*
Δb*





14.55
20.22
9.21
















TABLE 7







Inventive Test Sample #1 - Colored Area, Pre-Staining












Specimen
L
a*
b*







#1
90.74
−4.38
−7.49



#2
89.95
−4.35
−7.55



#3
90.03
−4.73
−8.31



#4
90.35
−4.45
−7.76



#5
90.54
−4.56
−7.64



Average
90.32
−4.49
−7.75

















TABLE 8







Inventive Test Sample #1 - Colored Area, Post-Staining












Specimen
L
a*
b*







#1
77.11
6.83
−2.18



#2
71.30
6.91
−3.79



#3
76.32
6.94
−2.10



#4
76.47
5.61
−3.18



#5
78.95
5.75
−2.93



Average
76.03
6.41
−2.84

















TABLE 9







Inventive Test Sample #1 - Colored Area, Average ΔL, Δa*, Δb*









ΔL
Δa*
Δb*





14.29
10.90
4.91









As shown above absorbent articles according to the present invention are resistant to red staining, or in other words resistant to Δa*. In addition, the colored portion of absorbent articles provide resistance to red staining while at the same time being “light” in color prior to use. Preferably, the colored portion of the absorbent articles according to the present invention has an average L value prior to staining of L>80 and more preferably L>85. In addition, the inventive article in the colored portion, after staining, has a Δa* of less than 18, more preferably less than 15, and most preferably less than 12. In this manner, the absorbent articles of the present invention provide a clean, light, appearance to the user prior to use while at the same time minimizing the red characteristics of the stain after use.
Test Method for Measuring Color Change In Response to Staining Within Noncolored Portion of the Article
After testing each of products within the colored portions of the article, each of the articles should be tested in an identical fashion in the noncolored portion of the article. In order to carry out this test method, five new clean samples of each product to be tested are required. Five specimens of each of the comparative samples and inventive sample were tested.
The noncolored portion of the article should be tested for L, *a, and b* values at a noncolored area that is closest to the portion of the article adapted to be arranged over the vaginal opening during use. In this manner, the article is tested at a noncolored area that is likely to be stained by menstrual fluid during use. L, a*, and b* values are measured for the noncolored portion for five specimens and the average L, a* and b* values are calculated. Thereafter, the noncolored portion is stained in the same manner described above for with respect to the colored portion. L, a*, and b* values are recorded for five different stained specimens and the average L, a*, b* values are recorded.
After the average L, a* and b* values have been calculated for both the clean and stained article, the average change in L, i.e. ΔL, the average change in a*, i.e. Δa*, and the average change in b*, i.e. Δb*, are calculated. Tables are provided below setting forth the measured values for Comparative Test Sample #1, Comparative Test Sample #2, and Inventive Test Sample #1.







TABLE 10







Comparative Test Sample #1 - Noncolored Area, Pre-Staining












Specimen
L
a*
b*







#1
94.73
−0.81
0.44



#2
95.29
−0.87
0.43



#3
95.09
−0.74
0.45



#4
95.84
−0.70
0.40



#5
93.82
−0.78
0.45



Average
94.95
−0.78
0.43

















TABLE 11







Comparative Test Sample #1 - Noncolored Area, Post-Staining












Specimen
L
a*
b*







#1
68.35
15.92
1.64



#2
67.78
16.08
1.50



#3
68.14
15.03
0.94



#4
67.17
15.39
1.08



#5
67.94
16.11
1.41



Average
67.88
15.71
1.31

















TABLE 12







Comparative Test Sample #1 - Noncolored Area, Average ΔL, Δa*, Δb*









ΔL
Δa*
Δb*





27.07
16.49
0.88
















TABLE 13







Comparative Test Sample #2 - Noncolored Area, Pre-Staining












Specimen
L
a*
b*







#1
97.05
−0.60
1.07



#2
96.17
−0.79
1.89



#3
94.94
−0.82
1.35



#4
95.30
−0.76
1.51



#5
94.83
−0.88
1.50



Average
95.66
−0.77
1.46

















TABLE 14







Comparative Test Sample #2 - Noncolored Area, Post-Staining












Specimen
L
a*
b*







#1
72.20
20.91
5.43



#2
72.94
21.84
5.90



#3
73.33
21.42
5.97



#4
72.63
20.94
4.97



#5
72.16
22.84
6.23



Average
72.65
21.59
5.70

















TABLE 15







Comparative Test Sample #2 - Nonolored Area, Average ΔL, Δa*, Δb*









ΔL
Δa*
Δb*





23.01
22.36
4.24
















TABLE 16







Inventive Test Sample #1 - Noncolored Area, Pre-Staining












Specimen
L
a*
b*
















#1
93.10
−0.80
−0.20



#2
95.85
−0.96
1.23



#3
96.84
−0.74
1.29



#4
96.45
−0.86
1.42



#5
92.73
−0.70
−0.12



Average
94.99
−0.81
0.72

















TABLE 17







Inventive Test Sample #1 - Noncolored Area, Post-Staining












Specimen
L
a*
b*







#1
76.83
11.02
0.66



#2
77.82
12.68
1.40



#3
77.40
11.66
1.37



#4
77.60
12.14
1.17



#5
77.20
13.61
2.37



Average
76.97
12.22
1.39

















TABLE 18







Inventive Test Sample #1 - Colored Area, Average ΔL, Δa*, Δb*









ΔL
Δa*
Δb*





18.02
13.03
0.67









The above data shows that even the noncolored portions of the napkin according the present invention show resistance to red staining as indicated by the low Δa* reading.

## Claims

1. A sanitary napkin comprising:
a body facing surface;
a portion adapted to be arranged over the vaginal opening during use;
a first colored portion, said colored portion extending over at least the portion of the napkin to be placed over the vaginal opening during use;
a noncolored portion;
wherein said first colored portion has a first color as measured from said body facing surface prior to staining;
wherein said first colored portion has a second color as measured from said body facing surface after staining;
wherein said first color has an average L value greater than 80; and
wherein a Δa* between said first color and said second color is less than 18.

2. The sanitary napkin according to claim 1, wherein said Δa* between said first color said second color is less than 15.

3. The sanitary napkin according to claim 1, wherein said Δa* between said first color said second color is less than 12.

4. The sanitary napkin according to claim 1, wherein said first color has an average L value greater than 85.

5. The sanitary napkin according to claim 1, wherein said napkin includes an imaginary longitudinal centerline and an imaginary transverse centerline and said first colored portion extends along said longitudinal centerline.

6. The sanitary napkin according to claim 5, wherein said first colored portion is arranged such that it is symmetrical with respect to the longitudinal centerline and the transverse centerline.

7. The sanitary napkin according to claim 1, further comprising:
a second colored portion.

8. The sanitary napkin according to claim 7, wherein said second colored portion comprises a ring that extends around said first colored portion.

9. The sanitary napkin according to claim 8, wherein said ring is spaced from said first colored portion such that a noncolored area is located between said first colored portion and said second colored portion.

10. The sanitary napkin according to claim 9, wherein said ring has a width in the range of about 1 mm to about 5 mm.

11. The sanitary napkin according to claim 1, wherein said first colored portion extends over about 15% to about 40% of the surface of an absorbent portion of the napkin.

12. The sanitary napkin according to claim 11, further comprising a second colored portion, wherein said second colored portion extends over about 3% to about 12% of the surface of an absorbent portion of the napkin.

13. The sanitary napkin according to claim 1, further comprising:
a cover layer;
a barrier layer; and
a colored layer arranged between said cover layer and said barrier layer.

14. The sanitary napkin according to claim 1, wherein said first color has an average L value of between about 80 and about 92, an average a* value of between −6.0 and −3.5 and an average b* value of between about −5.0 and about −10.

15. The sanitary napkin according to claim 14, wherein said first color has an average L value of between about 85 and 92, an average a* value of between about −5.5 and about −4.0 and an average b* value of between about −7.0 and about −9.0.

16. The sanitary napkin according to claim 1, wherein noncolored portion has an average, L, a*, and b* value as measured from said body facing surface prior to staining;
wherein said noncolored portion has an average, L, a* and b* value as measured from said body facing surface after staining; and
wherein a Δa* between the average a* value before staining and the average a* value after staining is less than 16.

17. The sanitary napkin according to claim 16, wherein said Δa* is less than 15.

18. The sanitary napkin according to claim 16, wherein said Δa* is less than 14.