CA2234154A1 - Microstructured polymeric substrate - Google Patents

Microstructured polymeric substrate

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Publication number
CA2234154A1
CA2234154A1 CA 2234154 CA2234154A CA2234154A1 CA 2234154 A1 CA2234154 A1 CA 2234154A1 CA 2234154 CA2234154 CA 2234154 CA 2234154 A CA2234154 A CA 2234154A CA 2234154 A1 CA2234154 A1 CA 2234154A1
Authority
CA
Canada
Prior art keywords
surface
plurality
polymeric
polymeric substrate
resilient
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
CA 2234154
Other languages
French (fr)
Inventor
Jennifer M. Aamodt
James G. Berg
Harlan L. Krinke
Clyde D. Calhoun
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
3M Co
Original Assignee
Minnesota Mining And Manufacturing Company
Jennifer M. Aamodt
James G. Berg
Harlan L. Krinke
Clyde D. Calhoun
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to US54237995A priority Critical
Priority to US08/542379 priority
Application filed by Minnesota Mining And Manufacturing Company, Jennifer M. Aamodt, James G. Berg, Harlan L. Krinke, Clyde D. Calhoun filed Critical Minnesota Mining And Manufacturing Company
Publication of CA2234154A1 publication Critical patent/CA2234154A1/en
Application status is Abandoned legal-status Critical

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Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C59/00Surface shaping of articles, e.g. embossing; Apparatus therefor
    • B29C59/02Surface shaping of articles, e.g. embossing; Apparatus therefor by mechanical means, e.g. pressing
    • B29C59/022Surface shaping of articles, e.g. embossing; Apparatus therefor by mechanical means, e.g. pressing characterised by the disposition or the configuration, e.g. dimensions, of the embossments or the shaping tools therefor
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C59/00Surface shaping of articles, e.g. embossing; Apparatus therefor
    • B29C59/02Surface shaping of articles, e.g. embossing; Apparatus therefor by mechanical means, e.g. pressing
    • B29C59/022Surface shaping of articles, e.g. embossing; Apparatus therefor by mechanical means, e.g. pressing characterised by the disposition or the configuration, e.g. dimensions, of the embossments or the shaping tools therefor
    • B29C2059/023Microembossing
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C59/00Surface shaping of articles, e.g. embossing; Apparatus therefor
    • B29C59/02Surface shaping of articles, e.g. embossing; Apparatus therefor by mechanical means, e.g. pressing
    • B29C59/04Surface shaping of articles, e.g. embossing; Apparatus therefor by mechanical means, e.g. pressing using rollers or endless belts

Abstract

A method of preparing a polymeric substrate having a surface which includes a plurality of microaberrations (5a, 5b) is provided. A polymeric material (1) in a flowable state is contacted with a resilient surface (9) to form microaberrations (5a, 5b) which are inverted replicas of microaberrations (4a, 4b) present on the resilient surface. A cleaning article and a slip control material which include the microstructured polymeric substrate are also provided.

Description

CA 022341~4 1998-04-06 wo 97/13633 PCT/uss6ll482 MICROSTRUCTURED POLYMERIC SUBSTRATE

Back~round of the Invention Polymeric substrates with a rnicrostructured pattern on their surface have a s wide variety of potential applications. Microstructured polymeric films may be appliecl to a surface in order to improve its slip control plupe~lies, e.g., to improve the grip on tools or athletic equipment. Other surfaces which may benefit from the applica.tion of materials providing el-hAl-ced slip control include traffic bearing surfaces, such as stairs, floors and rarnps.
Polymeric substrates with a suitably textured surface may also be employed in cle~ning articles. For example, non-abrasive polymeric scouring pads may be used for cle~ning dishes or pots or for removing insects and other debris from windows. Polymeric materials have desirable physical properties for fabricating cleaning pads while offering the potential for very economical production costs.A variety of methods for producing polymeric films having a textured surface are known. For example, an embossed therrnoplastic film having a plurality of micro depressions hllpal Led by placing a coarse sandblast pattern on a metalembossing roll is disclosed in U. S. Patent No. 5,229,186 (Tribble et al.). Similarly, U. S. P;atent No. 4,861,635 (Carpenter et al.) describes the replication of negative images of microtopographical features from a metal chill roll or a TeflonTM covered metal roll onto a polypropylene film. U.S. Patent No. 4,463,045 (Ahr et al.) discloses the p~ ep~lion of a plastic web having a microscopic pattern of surface aberrat.ions by cont~cting a heated thermoplastic film with a photoetched metallic laminal which has a microscopic pattern of surface aberrations on the uppermost 2s lamina The formation of a therrnoplastic sheet having a plurality of "nubbles" is disclosed in U.S. Patent Nos. 4,239,286 (Louis et al.) and 4,327,730 (Sorenson).The nubbles are formed by cont~cting a ribbon of thermoplastic film with a texturi:ng cylinder coated with a mixture of particles (e.g., ~ mim~m oxide particles) and cured epoxy. An article with a microstructure-bearing surface is described in U.S. Patent No. 4,576,850 (Martens). The article is formed by filling a mold CA 022341~4 1998-04-06 master, which bears a microstructure, with a radiation curable oligomeric composition.
U.S. Patent Nos.4,772,444 (Curro et al.) and 5,221,276 (Battrell) disclose a microlbubbled polymeric web. The microbubbles are produced by s~lbjectin~ a flats polymleric film supported on a fine woven wire mesh to a high pressure liquid jet.
In order for the articles co"~ , microstructured polymeric materials to realize their full potential, versatile, inexpensive methods of fabricating suchpolymeric materials must be available. Current methods do not readily allow controlled variations in the shape, orientation and positioning of a microscale texturing pattern on a polymer surface. In addition, current methodology typically only permits the generation of polymeric substrates in which the microstructure is limiteld to either the bottom of depressions or the tops of projections; it does not provide microstructure on the sides of macroscopic features such as depressions or projections nor does it permit a choice as to the type of microstructure generated.
A need, the~ erol e, continues to exist for improved methods of producing polynleric substrates having a surface textured with a defined microscopic pattern.
Optimally, such a method would also permit the introduction of macroscopic structural features (e.g., via embossing) and/or would allow the choice of generating a microscopic pattern on either all or a portion of the surface.
Summary of the Invention The present invention provides a method of prepa~ing a polymeric substrate having a surface which inrl~ldes a plurality of microaberrations. The method inclu(les cont~cting a flowable polymeric material with a resilient surface to form 2s the mlicroaberrations. The microaberrations produced on the polymeric surface are typically inverted replicas of microaberrations on the resilient surface, i.e., if the resilient surface incl~ldes a plurality of microdepressions, the polymer substrate which is generated will include a plurality of microprotrusions.
The present method also allows the formation of macroscopic features on the microstructured polymeric substrate. By incorporating embossing techniques, the present method permits the formation of polymeric substrates which include a plurality of projecting elements having microaberrations on their outer surface. In particular, the method allows the formation of microaberrations on the side walls of the projeclh~g rle .~ç~.ls If desired, the present method permits the introduction of microalbel.~lions onto the entire surface ofthe polymeric sub~ le~ i.e., on the portions ofthe surface in between the projecting ele.n~nt~ (the "land area") as well as on the projecting elemçntc themselves. The method also allows microaberrations to be glenerated only on the outer surface of the projecting el~.m~nts and not on the land area.
In addition, the present method allows the production of a microstructured polymeric substrate having microaberrations with a variety of controlled shapes and sizes. The method may be employed with a wide range of polymeric materials capable of existing in a state which is sufficiently flowable to allow the polymer to conforrn to the resilient surface and are capable of being at least partially solidified under the processing conditions. The present method allows the economical production of a wide variety of polymeric articles having a microstructured surface which rnay optionally be sim--lt~neously embossed to introduce macroscopic features.
The present method also provides a polymeric substrate having a plurality of projecting elements. The outer surface of the projecting elements has sidewalls which include a plurality of micl Opl oll usions. The mic- Opl oll llsions typically have a width and heighth of about lO~m to about 400~1m.
In another embodiment, the present method provides a unitary polymeric substral:e which includes a plurality of undercut-shaped solid micloplol"lsions. The polymeric substrate may also include a plurality of projecting clen~enls having the 2s mic~opl ~ sions on their outer surface.
Yet another embodiment of the present invention is directed to a dual structured polymeric substrate which includes a plurality of projecting elements.
The ou1er surfaces of the projecting elements have sidewalls which include a plurality of microaberrations.
'The present invention is also directed to cleaning articles and slip control materials which include the microstructured polymeric substrate. The CA 022341~4 1998-04-06 microstructured polymeric substrate may be formed by a process which inrludes cont~ctin~ a flowable polymeric material with a resilient surface which has a plurality of first microaberrations. A microstructured polymeric substrate formed in this m;mner in~ludes a plurality of second microaberrations which are inverted replica.s of the first microabel I alions.

Brief Desc~ ion of the Dlawin~,s Fig. 1 depicts a simplified schematic illustration of one embodiment of a method for producing a nliclos~ ctured polymeric film according to the present o invention.
Fig. 2 depicts a simplified schematic illustration of another embodiment of a method for producing a microstructured polymeric film according to the present invention.
Fig. 3 depicts a simplified sçhem~tic illustration of a third embodiment of a method for producing a microstructured polymeric film according to the present invention.
Fig. 4 depicts a simplified sch~m~tic illustration of a fourth embodiment of a method for producing a microstructured polymeric film according to the present invention.
Fig. S depicts a cross sectional view of a portion of a polymeric substrate of the present invention.
Fig. 6 shows an electron micrograph (12 X magnification) of a surface of a polymeric substrate of the present invention.
Fig. 7 shows an electron micrograph of one projecting element from the polymeric substrate depicted in Fig. 6 shown at a higher magnification (60 X
magnification) .
Fig. 8 shows an electron micrograph (15 X magnification) of a surface of a polymeric substrate of the present invention. The surface inr.ludes a plurality of projec~il,g elern~nts overlayed with a secondary structure of a plurality of raised ribs.

CA 022341~4 1998-04-06 Fig. 9 shows an electron micrograph (~0 X m~gnific~tion) of a projecting elçment from a polymeric substrate of the present invention. The outer surface of the projecting elçm~nt inçludes a plurality of cube corner out-shaped micr~prc,l, ~lsions.
Fig. 10 shows an electron micrograph (50 X magnification) of a projecting element from a polymeric substrate of the present invention. The outer surface of the projecling Çle~ -n~ inçludes a plurality of cube corner in-shaped microdepressions .
Fig. 11 shows an electron micrograph (95 X magnification) of a projecting lo element from a polymeric substrate of the present invention. The outer surface of the projecting element in~ des a plurality of partially spherical microdepressions.
Fig. 12 shows an electron micrograph (60 X magnification) of a projecting element from a polymeric substrate of the present invention. The outer surface of the projecting elçm~nt inrl~des a plurality of undercut-shaped mic~ op-ol, llsions.
Fig. 13 shows an electron micrograph (18 X magnification) of a projecting elemerlt from a polymeric substrate of the present invention. The outer surface of the projecting elçmçnt in~.lndes a plurality of miclopro~ sions.
Fig. 14 shows an electron micrograph (13 X magnification) of a surface of a polymeric substrate of the present invention. The surface inçlndes a plurality of discontinuous projecting elements in the form ridges incl~lrling a plurality of undercut-shaped micropro~ sions. The substrate surface also in~.ludes a plurality of mic,. opro~ sions.
Fig. 15 shows an electron micrograph (13 X magnification) of a surface of a polymeric substrate of the present invention. The surface in~.lucles a plurality of undercut-shaped micloplo~ sions.
Fig. 16 depicts a cross sectional view of a portion of a master used to prepane a microstructured polymeric substrate of the present invention.

Detailed Description of the Invention Fig. 1 depicts a sch~m~tic illustration of one embodiment of the present invention. A polymeric material 1 in a flowable state is brought into contact with a CA 022341~4 1998-04-06 resilient surface, such as the circull~el e~ al surface of resilient roll 2. Resilient roll 2 includes an outer layer of resilient material 9 covering a cylindrical core 11. The core 11 is typically formed from a subst~nti~lly non-resilient material, such as a metal or a high durometer rubber. In zone A, the polymeric material is in a flowable state and has relatively smooth major surfaces 7 and 8. The polymeric material may enter z;one A already in flowable state, e.g., after exiting the die of an extruder.
Alternatively, the polymer may be treated in zone A, such as by the application of heat, to transform the polymer into a flowable state. During procçs~i~, the flowable polymeric material comes into contact with the surface 3 of resilient roll 2 in zone B. Sufficient pressure is exerted in the nip on the flowable material bysmooth roll 10 and resilient roll 2 to force the polymeric material to conform to the contours of surface 3. The flowable polymer is forced into any l ecesses or crevices defined by the microdepressions 4 present in surface 3. This results in the generation of microscopic projections 5a, 5b ("microprotrusions") on the polymeric surface 7 which comes into contact with resilient surface 3. The microprotrusions 5a, Sb formed on the polymeric surface 7 are inverted replicas of the corresponding microdepressions 4a, 4b in resilient surface 3. While still in contact with the resilient surface 3, the polymeric material solidifies to a sufficient degree to allow the microprotrusions 5a, Sb to retain their shape (see zone C) as the microstructured polymeric film 6 is pulled away from the surface 3 and the microprotrusions 5a, Sb are pulled out of microdepressions 4a, 4b. This may be accoml~!ished, for example, where the polymeric material is formed from a thermoplastic polymer by ~ ;n~ ;n~ the te--~peral-lre of the resilient roll 2 below the softening point of the polymeric material. Alternatively, where the polymeric material has thermoset properties, the solidification may be achieved by applying additional heat to the polymeric material while the material is in zone B, e.g., by ",~ in~ smooth roll 10 at an elevated ten~pe~LLIre.
The material which forms the surface 3 of resilient roll 2 typically permits the mic,rostructured film 6 to be separated from resilient roll 2 without substantially 3n distorting or destroying the microaberrations 5. This requires that the forming microstructured film 6 does not adhere to resilient surface 3. The outer surface of CA 022341~4 1998-04-06 3 pcTluss6ll482s resilient roll 2 may also be forrned from a number of resilient materials which perrnit the processed polymer to be removed without problems of adhesion. In a prerel,c;d embodiment of the invention, resilient surface 3 is formed from a silicone rubber.
iellt materials formed from polyurethane or silicone permit the present method to be carried out under a wide range of processing conditions, e.g., temperatures from albout 0~C to about 400~C or even higher.
The interaction belween microaberrations 5, which are at least partially solidified, and the resilient roll surface 3 is such that the microaberrations 5subst~nti~lly retain their shape as the microstructured polymeric film 6 is pulled 0 away firom the resilient roll 2. To some extent this may be due to some resiliency on the part of the microaberrations 5 themselves, as where the solidifying polymeric material exhibits some degree of elasticity. More typically, the resilient interaction is achieved by the resiliency of the resilient roll surface material 9.
The resilient roll 2 may be covered with an outer layer of a porous resilient material, such as a polymeric foam. Exall~ples of suitable foams for the resilient surface include polyurethane foams and silicone foams. The foam may be a closed cell polyurethane foam such as LS1525 polyurethane foam (available from EAR
Specialty Composites Corporation, Tn~i~n~polis, IN) or PORONlM polyurethane foam (available from Rogers Corporation, East Woodstock, CT). The closed cell polyurethane foams disclosed in U.S. Patents 3,772,224 and 3,849,156, may also be employed for the resilient surface. Another example of a suitable polymeric foam is a closed cell silicone foam such as Bisco BF-1000 foam (available from Bisco Products, Elk Grove, IL). The resilient polymeric material may also include an open cell polymeric foam. Alternatively, the resilient surface may be covered with a layer of a nonporous flexible material, e.g., a flexible polymeric material such as a silicone rubber. For example, the resilient surface may include SilasticlM brand J-RT~ silicone rubber (col",l,er-,ially available from Dow Corning Corp., Midland,MI). Resilient surfaces having defined microstructural features preferably include a silicone rubber. Alternatively, where the resilient surface has a foam microstructure, the resilient material preferably inrll~des a closed cell polyurethane foam, such as described in U.S. Patents 3,772,224 and 3,849,156.

CA 022341~4 1998-04-06 The resilient material which forms resilient surface 3 may inherently include microaberrations 4, e.g., the pocket-like depressions present in the surface~of a polymeric foam. Where the resilient surface includes a polymeric foam material, the resilient surface may also include a thin outer layer of a nonporous flexible material s covering the foam. For example, the resilient surface may include a foam layer covered by a thin layer (e.g., about 0.5 mm to about 1.0 mm) of silicone rubber.The thin silicone rubber layer may include microaberrations on its surface.
The resilient surface may also be formed by w~ ai)p;.,g the roll with a nonporous flexible microstructured material. For example, a variety of substantially lo rigid microstructured surfaces may be coated with a thin layer of material (e.g., liquid silicone rubber) which is then cured into a flexible material reflecting the microstructure of the underlying rigid structure. A desired pattern and shape ofmicroprotrusions in a flexible material may also be generated by embedding a plurality of microscopic particles in the surface of a resilient material, such as by embed~ing inorganic particles (e.g., glass beads) in a silicone rubber layer.
Microdepressions may be formed in silicone rubber layer (or other nonporous flexible material) by removing microparticles embedded in the silicone rubber toleave a plurality of microdepressions in the rubber surface.
A wide variety of polymers may be processed according to the present methocl into a polymeric substrate having a microstructured surface. Polymeric materials capable of being sufflciently flowable to allow the polymer to conform to the mic:roscopic features of the resilient surface and capable of being solidified sl.ffi~ ntly to generate microscopic features on the polymer surface are suitable for use in the present invention. Typically, the polymeric material in~ludes a 2s thermoplastic polymer such as a polyolefin, although other polymeric materials capable of being processed in a flowable state, such as a B-staged thermoset polymer or a plastisol, may also be employed.
Typically, the polymeric material in~ dec a thermoplastic polymer having a melt tempe~ re above about 50~C. However, polymeric materials which exist in a flowable state at a considerably higher te"lpe,al~lre may also be employed. The physica.l p~ opc, lies of the resilient surface and the polymeric material must be CA 022341~4 1998-04-06 ,.,atched such that the microstructural features of the resilient surface are stable and resilient under conditions which permit the flowable polymer to co"ro"" t~- the resilient surface and then at least partially solidify. Preferably, thermoplastic materials which can be passed through an embossing nip at or slightly above their s glass transition te~pe~alLlre are employed, as such materials may be processed with short cycle times.
F.Y~ , les of suitable thc.",oplastic polymeric materiials which may be employed in the present process include polyolefins such as poly,~ropylene, polyethylene, and pol~l,rop~lene/polyethylene copolymers. Blends of polypropylene and/or polyethylene, such as a high/low molecular weight polyethylene blend (e.g., HostalloyTM 731; Hoechst Celanese, Somerville, N.J.), are also suitable for use in the present invention. Other suitable thermoplastic polymers include polyvinyl chloride (PVC), polyamides such as a nylon (e.g., nylon 6, nylon 6,6, or nylon 6,9), and polyesters. Olefin copolymers such as ethylene/vinyl acetate copolymers or copolymers of an olefin and an a,b-unsaturated acid (e.g., an ethylene/methacrylic acid copolymer reacted with metal salts to confer ionic character; available from E.I. du Pont de Nemours & Co., Inc. as SurlynlM 8527) may also be employed in the present invention. Preferably, the polymeric material inrllldes a polyolefin.
In another embotliment of the invention, the polymeric material may include a plastisol. The plastisol inr.l~ldes a dispersion of thermoplastic resin particles (e.g., polyviinyl chloride resin particles) in a pl~ctir.i7er and may also include a volatile organic solvent. Examples of suitable plastisols which may be used in the present method include the vinyl plastisols such as #D1902-S0 Black and #D1902-78 White available from Plast-O-Meric, lnc. (Wa..keeh~ WI).
The microaberrations generated on the polymeric substrate by the present method may have a wide variety of shapes and orientations. The microaberrations include microprol,-lsions and/or microdepressions. These may be in a random and/or ordered pattern. The microaberrations may include irregular shapes and/orregular geometric shapes, e.g., a plurality of discrete mounds, posts,- cones, tr~lnçated cones, pyramids, or trunçated pyramids. The microaberrations may include discontinuous shapes, i.e., a plurality of discrete projections or depressions.

CA 022341~4 1998-04-06 W O 97113633 PCT~US96/14825 Alternatively, the microaberrations may include continuous forms such as ridges and grooves The ~~im~n~ions of the microabell ~lions, however, are typically small enough to leave the form of any macroscopic features on the polymeric substrate subst~nfi~lly unaltered. Typically, discontinuous microaberrations have a m~xim ~im~n~ion (height or width) of no more than about 40011m. Preferably, discontinuous microaberrations have a m~imum height of no more than about 30011m and a m~lcimllm width of no more than about 300~m. More preferably, discontinuous microaberrations have a maximum height of no more than about 20011m and a Il~A~ II width of no more than about 20011m. Similarly, where the microaberrations are continuous in nature, the height and width of the microaberrations are typically no more than about 40011m, preferably of no more than about 300~,1m, and more p-erel~bly of no more than about 20011m. The microaberrations preferably have an average miniml~m height and width of at least about 10~m and more preferably at least about 2511m.
One distinct advantage of the present method is that it allows the generation of undercut-shaped microaberrations on the surface of a polymeric substrate. As used herein, the term "undercut-shaped" is defined as a shape having a cross-sectional surface area which increases and then typically decreases along a perp~nllicul~r vector away from the polymer surface. In other words, the cross-sectior-~l surface area is measured in a plane parrallel to the major surface of the polymeric substrate with respect to which the undercut-shaped microaberration in question is positioned.
The microstructured polymeric film 6 formed by the process illustrated in Fig. I includes a number of undercut-shaped micloplollusions Sa. The undercut-shaped mic, op~ oll usions are generated when the flowable polymeric material isforced into an undercut-shaped microdepression 4a in resilient surface 3. The parameters of the process (e.g., telllpel alure of the thermoplastic polymeric material in Zone A, temperature of the resilient surface 3, the compositions of the polymeric material and resilient surface 3, the speed at which the polymeric film is processed and pressure exerted on the forrning microstructured polymeric film) may be adjusted such that an undercut-shaped microprot~ usion ~a on the polymeric film CA 022341~4 1998-04-06 W O 97113633 PCTrUS96/14825 may be pulled out of an undercut-shaped microdepression 4a without subst~nti~llyaltering or distorting the shape of the mic~ oprol. usion.
In addition to f~rilitatin~. the ~genel~lion of a microstructured surface on a polyme,ric substrate, the use of a resilient surface having an outer res;lie"l layer of foam or silicone rubber has another advantage. The polymeric substrate may also be eimlllt~neously shaped or formed to introduce macroscopic features, e.g., by embossing, as part of the present method. Figure 2 shows a second embodiment of the present method. The resilience of outer layer 32 of chill roll 27 permits the film to be embossed without requiring that each projecting embossing cle~ l 21 be o prec;sely positioned with respect to a co--esponding recess in the opposing roll.
In the embodiment of the present method illustrated in Fig. 2, a flowable polymeric material 25, such as a softened thermoplastic polymeric film, is passed through a nip which ir cludçs embossing roll 20 and chill roll 27. Chill roll 27 is covered by a outer layer 32 of resilient material which has a plurality of microdepressions 28 in its outer surface 30 (e.g., the microdepressions present in the surface of a polymeric foam). When the so~çnçd thermoplastic polymeric film 25 is contacted with embossing roll 20 and chill roll 27, posts 21 are forced into the film and projecting elements 22 are formed. As this happens, the softened thermoplastic polymeric film 2~ is forced into intim~te contact with the surface 30 of chill roll 27. As with the method illustrated by Fig. 1, this results in the formation of mi-;l oproL~ ~Isions 23 on the portions of the polymeric material in contact with surface 30. The microprotrusions 23 are inverted replicas of the corresponding microdepressions 28 in the outer surface 3~ of chill roll 27. The resulting polymeric film 26 has a plurality of projecting elements 22 having a hollow core 29. The outer surface 24 of projecting el~mente 22 includes a plurality of the microprotrusions 23. In the process illustrated in Fig. 2, the microprotrusions 23 are generated on the top 24 and side 33 surfaces of projecting elements 22, but not on the land area 31 between adjacent projecting elements 22.
By controlling the nip pressure, the present process may be modified to produce microaberrations on either the outer surface of the projecting elements 22 or on the entire surface of the polymeric film (i.e., on the land area 31 between the CA 022341~4 1998-04-06 projecting elements 22 as well as on the outer surfaces 24, 33). The nip pressure may ble increased by a variety of techniques, inclll~ing but not limited to p-ositioning embossing roll 20 and chill roll 27 closer together, increasing the height of embossing pl~m-ont~ 21 or decreasing the density of embossing el~ment~ 21 (i.e.,increa.sing the spacing between ~djaççnt embossing PlemçntS 21 and decleasing the surfac,e area of embossing roll 20).
Fig. 3 illustrates a third embodiment of the present method. Softened thermoplastic polymeric film 46 is passed through a nip which incl~ldes embossing roll 40 and chill roll 41. Chill roll 41 is covered with two layers of resilient material, o an inrer layer of polymeric foam 43 and an outer layer 44 of nonporous flexible material, such as silicone rubber. The surface 47 of layer 44 has a microstructure which includes a plurality of microprotrusions 45. The nip pressure forces the softened polymeric film 46 into contact with embossing roll 40 and chill roll 41. As this occurs, posts 42 are pressed into the film 46 to form projecting elements 48.
During this process, the softened film 46 is forced into intim~te contact with the microstructured surface 47 of chill roll 41. As with the methods illustrated by Figs.
1 and 2, microscopic fealul es (microdepressions 49) are generated in the portions of the film 46 in contact with surface 47.
The microstructured polymeric film 50 produced by the method illustrated in Fig. 3 has a plurality of projecting elements 48 having a hollow core 51. The projecting elements 48 include a plurality of the microdepressions 49, which areinverted replicas of corresponding micl op~ ol~ ~lsions 45 in the outer surface 47 of chill roll 41. In the process illustrated in Fig. 3, the microdepressions 49 aregenerated on the land area 53 as well as on the top 52 and sidewall 54 surfaces of projecting elements 48. By controlling the nip pressure, it is also possible to cause the microscopic features to be generated only on the outer surfaces of the projecting çlem~nt~ (as illustrated in Fig.2).
The micl oproL. .lsions 4~ depicted in Fig. 3 may be formed from a flexible material, such as silicone rubber. The present method may also be carried out with a resilient surface which incllldes a plurality of nond~rol.ni,lg microscopic regions surrolmded by resilient material, e.g., a plurality of rigid microscopic particles CA 02234l~4 l998-04-06 WO 97/13633 PCT~US96/14825 partially embedded in the surface of a resilient material. For example, the resilient surface may be formed from a layer of silicone rubber which has a plurality of micloscopic inorganic particles (e.g., glass beads having a tli~met~r of about lOIlm to about 250~1m) partially embedded in surface of the rubber layer. Because of the flexibility of the underlying silicone rubber matrix, it is possible to generatemicrodepressions in the surface of a polymeric substrate which are substantiallyundistorted inverted replicas ofthe shape ofthe h~olgallic particles protruding from the silicone rubber surface. In other words, if the inorganic particles are spherical mic~ oscopic glass beads which partially protrude from the silicone rubber, a o plurality of microdepressions, which are shaped like a portion of a sphere, may be formed in the polymer substrate surface. In addition, due to the flexibility of the resilient surface, the present method permits the generation of embossed polymeric substrates having microdepressions and/or micl opro~ sions on the sidewalls of macroscopic structural features formed via embossing.
Fig. 5 depicts a portion of a polymeric film 80 which has been embossed according to the present method to generate a hollow projecting elemçnt 82. The projecting ~l~m~nt 82 inl ludes microdepressions on both its top outer surface 83 and its outer sidewalls 84. By employing the present method, it is possible to create microdepressions on the sidewalls of a projecting element such that the microdepressions are substantially undistorted inverted replicas of rigid mi~oprol, ~Isions on the resilient surface used to form the microstructured embossed polymeric substrate. Microdepressions having a partially spherical shape (see, e.g., microdepressions 81 in Fig. 5) may be formed by employing a resilient surface which includes rigid partially spherical shaped micloprotl~lsions, such as glass beads partially embedded in a resilient material.
Fig. 4 illustrates yet another embodiment of the present method. Resilient roll 60 includes an outer layer of resilient silicone rubber material 70. The surface 62 ofthe resilient material 70 incl~ldes a number of macroscopic depressions 63. In addition, the entire resilient surface 62 includes a plurality of microdepressions 64.
As the flowable polymeric material 69 is passed through the nip of resilient roll 60 and smooth roll 61, surface 68 of polymeric material 69 is forced into intim~te CA 022341~4 1998-04-06 contact with resilient surface 62. This causes the polymeric material to fill macroscopic depressions 63, thereby generating solid projecting .oiemP.ntc ~
n~lin~ from dual structured film 67. In the process illustrated in Fig. 4, the polymeric material is simult~neously forced into microdepressions 64, thereby generating a plurality of solid microprol- usions 66 on the entire surface of textured polymeric substrate 67 (i.e., on the land 72 as well as on the outer surface 71 of projecting elements 65).
The projecting elements formed by the present method may have a variety of heights. For example, the method allows the production of microstructured o projecting elements having a height within the range of about 0.375mm to about 2.5mm while avoiding substantial distortion of microaberrations generated on theouter sidewalls of the projecting elements. Moreover, the present method allows undistorted microaberrations to be formed in the sidewalls of projecting ~lem.onts which have a very steep draft. For example, sub~ y undistorted microaberrations may be formed on the sidewalls of projecting elements having a draft of less than about 30~ (with respect to a vector perpendicular to the major surface of the polymeric substrate). Subst~ntially undistorted microaberrations may be generated on sidewalls which are quite close to being vertical (i.e., have a draft of less than about 10~) or even on sidewalls which are substantially vertical (i.e., have a draft of less than about 5~). Using the present method, substantially undistorted micloprotlusions have been generated on the sidewalls of vertical (i.e., 0~ draft) 1.5mm high hollow posts. This unitary polymeric structure was generated by embossing a polypropylene film into a resilient roll covered with a layer of a closed cell polyurethane foam.
The microstructured polymeric substrates of the present invention may be used to form a slip control material. For example, a unitary polymeric sheet having microaberrations on one face may be afixed to traffic bearing surfaces, such as stairs, floors and ramps. Polymeric materials formed by the present method may also used to form the grip on tools or athletic equipment thereby providing enhanc.ed slip control.

CA 022341~4 1998-04-06 In yet another embodiment of the invention, the microstructured polymeric substrates of the present invention may be used to form a cle~ning article. ~
partic.ular, flexible polyrneric sheets which have been embossed to form a unitary polymeric structure having a plurality of microtextured pl ojeclin~ el~m~nts areuseful in clF~ g applications. Such a flexible sheet of polymeric material may be textured using the present method. Flexible sheets of this type may be utilized as a cle~ ng rag or may be afixed to a foam b~c~in~ to form a cl~nin~ pad.
The invention is further characterized by the following c,.alll?les. These examples are not meant to limit the scope of the invention as described in the foregoil~g description. Variations within the concepts of the invention will be appaltl~t to those skilled in the art.

Process Parameters Embossed polypropylene films were prepared by extruding polypropylene resin (DS7C50, available from Shell Chemical Co., Houston, TX) from a single screw extruder (Model DS15H, available from Davis Standard, Stalllrord, CT) equipped with a 3.8 cm ~ meter cylinder, into the nip of a two roll embossing a~)palalus. The extruder, which was operated at 254~C, delivered a 22.9 cm wide sheet of molten polypropylene through a 30.5 cm die having a 0.25 mm die gap at a rate of 55 g/m2, vertically downward into the nip of the embossing appalalus which was positioned about 7.6 cm below the die. The embossing appalalLIs utilized two24.5 cm diameter by 30.5 cm long steel rolls having independent telllpelalLIre controls. One of the rolls (the embossing roll) was heated to 49~C and carried an embossing pattern while the other roll (the chill roll) was cooled to 7~C and was covered with a resilient material. The polypropylene was embossed at a nip pressure of 138 kPa and line speed of 1.5 m/min.

Embossing Apparatus/Process II
An embossed polyethylene film was prepared by extruding polyethylene (DOWEXTM 2047A, available from Dow Chemical Co., Midland, MI) from a single screw extruder (Model 1.75 TMC30; ~'M Corporation, Mount Gilead, OH) CA 022341~4 1998-04-06 wo 97/13633 pcTlus96/l482s equipped with a 4.4 cm t~i~meter cylinder into the nip of a two roll embossing apparatus. The extruder, which was operated at 249~C and a screw rotational speed of 20 rpm, delivered a sheet of molten polyethylene through a 30.5 cm die having a 0.25 mm die gap ho- izol.Lally into the nip of a two roll embossing appa. alLls which s was positioned such that the width of the polyethylene film entering the nip was approxi--lately 15 cm. The embossing apparal~ls utilized a 25.4 cm ~ meter by 35.6 cm long steel roll (the embossing roll) which carried an embossing pattern and asimilarly sized 75 dulul~le~er rubber roll which served as the chill roll. The steel roll was heated to 15.6~C, while the rubber roll, which was covered with a resilient o material, was cooled to 0~C. The polyethylene was embossed at a nip pressure of 55 kPa and line speed of 3 m/min.

Embossin~ Roll Surfaces The embossing roll surfaces were generated by conventional photoengraving techniques on magnesium or a m~gne~ium alloy. Specific embossing patterns used in the following examples included:
EB-l A hexagonal close packed array of circular posts (1.0 mm in di~m~o,ter, 0.5 mm in height) which were spaced 1.9 mm on center.

A square lattice array of square posts (1.0 mm on a side, 1.0 mm in height) which were spaced 2.5 mm on center.

A square lattice array of circular posts (1.0 mm in diameter, 1.0 mrn in height) which were spaced 1.9 mm on center.

A herringbone pattern consisting of discontinuous ridges 1.5 mm in height and having top rect~ r surfaces 1.0 mm in length and 0.13 mm in width. The rect~n~ r base dimensions of the discontinuous ridges were larger than the top surface dimensions as the sidewall portions were inclined at an appro~ alely 25-30~ angle to a vector CA 022341~4 1998-04-06 perp~n~ic~ r to the face of the embossing roll. The center-to-center spacing of the ridges was 4.4 mm in the down web d~rection and 3.5 mm in the cross web direction. The ridges were positioned at a 30~ angle to the left or right of the down web direction, i.e., the rows of discontin~o-ls ridges alternated between 30~ left and right of the down web direction.

Chill Roll Covers Chill rolls were covered with one or more layers of foam, a resilient 0 patterned silicone rubber sheet or a l~min~te construction of a foam and a resilient patterned silicone rubber sheet. Specific foam materials that were used in th following examples included:

A 3.2 mm thick layer of polyurethane foam pl epa~ ed as generally described in U.S. Pat. Nos. 3,772,224 (Marlin et. al.) and 3,849,156 (Marlin et. al). The foam was prepal ed from a four part mix (A-D), the composition of which were:
Part A - 100 parts of a polyol mixture of consisting of Niax 24-32 (97.77 parts) and Niax E-434 (2.23 parts), polyether polyols (available from Arco Chemical Co., Newton Square, PA) dipropylene glycol (9.18 parts per hundred parts polyol (php);
fragrance grade), Niax LC-5615 (3.74 php, a nickel catalyst composition available from OSI Specialities, Lisle IL), ~hlmimlm trihydrate filler (54.59 php, Aloca C-331, available from ~lllmimlm Company of America, Rallxite, AR), and Hostaflam AP 442 flame retardant (16.38 php, available from Hoechst Celanese Corp., Charlotte, NC);
Part B - 37.39 php of an isocyanate mixture consisting of 4,4'-diphenylmeth~ne diisocyanate and a modified 4,4'-diphenylmethane diisocyanate (~nbin~te 1920 available from ICI, Rubicon Chemicals, Geismer, LA);

CA 022341~4 1998-04-06 WO 97tl3633 PCT/US96/14825 Part C - 4.77 php of a 70.9% (w/w) solution of a silicone surfactant (L-5614, available from OSI Sper~ ties) in a polyether glyco-l (Niax E-35 1, available from Arco Chemical Co.); and Part D - 6.71 php of an approx".,ately 8% solids (w/w) dispersion of s carbon black (Product No. 1607029, available from Spectrum Colors, Minneapolis, MN) in polyether glycol (Niax E-351).
Separate feed streams of the four parts were pumped into a 90 mm dual head Oakes Frother (available from ET Oakes Corp., Hauppauge, NY) through an entrance manifold ~tt~r.hçcl to the frother. The mixture was frothed by injecting high purity nitrogen through a capillary tube located at the entrance to the frother. The frothed mixture was processed through the frother at a mixing speed of 800 rpm and a discharge pressure of about 0.55 M:Pa and dispensed from an approximately 2.6 m x 1.3 cm hose onto a polyester film and spread over the film using a knife coater (2.4 mm gap). The foam was cured by passage through a 3 chambered 13.7 m forced air oven at a line speed of 1.5-1.8 m/minute. The first chamber was m~int~ined at 135~C. The second and third chambers were m~int~ined at 154~C.

A 6.3 mm thick layer closed cell silicone foam (Bisco BF-1000, available from Bisco Products, Elk Grove, IL).

Patterned silicone rubber sheets used alone or in silicone rubber sheet/foam l~min~te chill roll cover constructions were prepared by applying an appro~u,,,ately 0.8 mm thick coating of uncured silicone rubber (Silastic brand J-RTV silicone rubber, available from Dow Corning Corporation, Midland, MI) over a structured surface, curing the silicone rubber at 66~C for one hour, and removing the curedpatterned silicone rubber sheet to provide a resilient replica of the structuredsurface. Specific silicone rubber sheet patterns and silicone rubber sheet/foam l~minsl~e constructions used in the following examples inchlded:

CA 022341=,4 1998-04-06 A silicone rubber sheet having a pattern of parallel raised ribs 0.18 mm in height and spaced 0.36 mm apart, the sides of which intersect at a 90~ angle, which was replicated from the surface of Optical T.i~hting Film (3M, St. Paul, MN). This silicone rubber sheet was laminated to a layer of the closed cell polyurethane foam RC-l, described above, to form a chill roll cover material.

A silicone rubber sheet having a pattern of cube comer I ecesses 0.18 o mm in depth with a base triangle having angles of 55~, 55~, and 70~, replicated from the surface of a cube corner reflective polycarbonate film as described in U.S. Pat. No. 4,588,258 (Hoopman).

A silicone rubber sheet having a pattern of cube corner protrusions 0.09 mm in height arrayed in a pattern similar to that of RC-4.

A silicone rubber sheet having a random pattern of spherical projections (ranging from approximately 10-25% of a total sphere).
The silicone rubber sheet was plepaled by (1) randomly capturing glass beads, about 55 mm in diameter, in a 5 mm (dry thickness) adhesive (F-10, an acrylic base adhesive con~ining a solvent vehicle, available from Rohm & Haas, Philadelphia, PA) coated on polyethylene coated Kraft paper; (2) coating silicone rubber (Silastic brand J-RTV silicone rubber) over the glass beads using a knife coater with a coating gap of 0.5 mm; (3) placing the uncured coating in a partial vacuum to remove e~ pped air; (5) curing the degassed coating at 70~C for two hours, and (6) removing the cured silicone rubber from the adhesive coated Kraft paper.

A silicone rubber sheet having a random pattern of spherical depressions (ranging from approximately 75-90% of a total sphere) CA 022341~4 1998-04-06 prepared by removing the glass beads from roll cover RC-6. The glass beads were removed by applying ScotchTM 810 MagicTM
Mending Tape (available from 3M, St. Paul, MN) to the glass bead co..l~ n~ surface and flexing the silicone film as the adhesive tape was removed.

Example 1 An embossed polypropylene film was prepaled using Embossing Apparatus/Process 1, incorporating an embossing roll having a hexagonal array ofo circular posts (EB-l) and a closed cell polyurethane foam chill roll cover (RC-1).
Electron photomicrographs of the face of the embossed film that had been in contact with the chill roll cover (see Figs. 6 and 7) show projecting elçm~nts consisting of a hexagonal close packed array of hollow circular posts covered with microaberations consisting of a plurality of microprotrusions corresponding to inverted replicas of surface pores in the foam chill roll cover, many of which had an undercut structure. The microprotrusions, which covered the top and side surfaces of the posts, were not present on the land area or surface area between the projecting elements.

Example 2 An embossed polypropylene film was prepared according to the procedure of Example 1 except that the embossing roll had a square lattice array of squareposts (EB-2) and the chill roll cover was a silicone rubber sheet having a ribbed pattem. which was l~min~ted to a layer of polyurethane foam (RC-3). An electron photomicrograph (see Fig. 8) of the face of the embossed polypropylene film, which had been in contact with the chill roll cover, shows projecting elPments consisting of a square lattice array of hollow square posts. The surfaces of the square posts were covered with an array of protruding parallel ribs. The ribs were observed on the top and side surfaces of the posts as well as the land area between the posts.
This experiment demonstrates that in generating microaberations in a polymer film which are inverted replicas of microaberations on the surface of a resilient chill roll, the shape of the microaberations need not be limited to pores in the surface of a foam.

Example 3 An embossed polypropylene film was prepared according to the procedure of Example 1 except that the embossing roll had a square lattice array of circular posts (EB-3) and the chill roll cover was a silicone rubber sheet having a cube corner recess pattern (RC-4). An electron photomicrograph (see Fig. 9) of the face of the embossed polyl l op~lene film that had been in contact with the chill roll cover 0 shows projecting eletnent~ cons;sling of a square lattice array of hollow circular posts. The top and side surfaces of the posts were covered with a pattern of protruding cube corners. The land area between the posts was smooth.

ExamPle 4 An embossed polypropylene film was plepared according to the procedure of Example 2 except that the chill roll cover was a silicone rubber sheet having cube corner projections (RC-5). An electron photomicrograph (see Fig. 10) of the faceof the embossed polypropylene film which had been in contact with the chill rollcover showed projecting elements consisting of a square lattice array of hollow square posts. The top and side surfaces of the posts were covered by an array ofrecessed cube corners ("microdepressions"). The land area between the posts was also covered the same array of cube corner microdepressions.

Example ~
A 5 cm square piece of flat tooling with a square lattice array of square posts ( 1.0 mm on a side, 1.0 mm in height) spaced 2.0 mm on center was heated to 193 C on a hot plate. A 0.26 mm thick piece of polypropylene (DS7C50) film was placed on the patterned side of the tooling and heated until the polypropylene film softened (approximately 1 minute). Once softened, the polypropylene film was covered with a silicone rubber sheet embedded with glass beads (RC-6) such that the bead co..~ .;..g surface contacted the softened polypropylene. Two layers of CA 022341~4 1998-04-06 the cllosed cell polyurethane foam chill roll cover (RC-l) were placed on top of the silicone rubber sheet, the assembly removed from the hot plate, and pressure applied to the assembly by means of a hand held platen until the polypropylene solidified.
An electron photomicrograph of the face of the embossed polypropylene film that s had been in contact with the silicone rubber sheet showed a square lattice array of projecting hollow square posts (see Fig. 11) covered with microaberations. The microaberations con.~ieted of a random array of spherical microdep, ess;ons (ranging from appl oximately 10-25% of a total sphere). The microdepression pattern was observed on the top and side surfaces of the posts as well as the land area between o the posts.

Example 6 An embossed polypropylene film was prepared according to the procedure of Example S except that the silicone rubber sheet had a random pattern of spherical microdepressions (RC-7). A number of the spherical microdepressions had an undercut shape. An electron photomicrograph of the face of the embossed polypropylene film that had been in contact with the silicone rubber sheet showed a unitaly structure which included a square lattice array of projecting hollow square posts (see Fig. 12) covered with a pattern of microaberations. The microaberations consisted of a random array of spherically shaped polypropylene mic~oploll~lsions.
The microprotrusion pattern was observed on the top and side surfaces of the posts as well as the land area between the posts. Since the polypropylene micl opl ot. ~Isions were inverted replicas of the microdepressions in the silicone rubber sheet, a number of the mic--oplot- ~Isions had a spherical undercut shape.
Example 7 An embossed polyethylene film was prepared using Embossing Apparatus/Process II, incorporating an embossing roll having a square lattice array of square posts (EB-2) and a closed cell silicone foam chill roll cover (RC-2). An electron photomicrograph (see Fig. 13) ofthe face ofthe embossed polyethylene that had been in contact with the chill roll cover shows a primary structure CA 022341~4 1998-04-06 consisting of a square lattice array of projecting hollow square posts covered with micrc,abe,~lions. The microaberations consisted of a random array of microp, oll llsions col I ~s~onding to inverted replicas of the surface pores in the foam chill roll cover. The micloprol~lsions were observed on the side surfaces as well as on the tops of the posts.

Example 8 An embossed film was prepared using a procedure similar to the procedure of Example 7. An ethylene/propylene copolymer (KS-057, available from Himont lo USA, Inc., Wilmin~on, DE) was substituted for the polyethylene resin. Theembossing roll had a herringbone pattern of discontinuous ridges (EB-4). The chill roll was covered with a layer of a closed cell polyurethane foam (RC-I). The ethylene/polypropylene copolymer was processed at a nip pressure of 6.9 kPa and line speed of 1.5 m/min. The temperatures ofthe inlet fluids to the embossing roll and chill roll were 15.6~C and 0~C, respectively. An electron photomicrograph (see Fig. 14) ofthe face ofthe embossed film that had been in contact with the chill roll cover showed of a herringbone pattern of discontinuous ridges covered with a plurality of microprot~ usions. The micropl oll ~Isions col ~ esl)onded to inverted replicas of the surface pores in the foam chill roll cover.
Example 9 An embossed polypropylene film was prepared using Embossing Apparatus/Process I except that a smooth steel roll, which was ...A;~ ed at 54~C, was substituted for the embossing roll. The extruder was operated at 266~C, and the polyprowlene was delivered at a rate of 159 g/m2. The chill roll was coveredwith a closed cell urethane foam (RC-1). An electron photomicrograph of a cross-section ofthe res~lting unitary microstructured film (Fig. 15) showed a plurality of ~iclopro~ sions on the face ofthe embossed film which had been in contact with the chill roll. The micloprolnlsions corresponded to inverted replicas of the surface pores of the foam chill roll cover. Many of the mic~ op~ oll ~Isions showed an undercut-shaped structure.

CA 022341~4 1998-04-06 ~ WO 97/13633 PCT/US96/14825 Examples 10-13 --A series of embossed films were prepared using Embossing Apparatus/Process 1 except that a variety of thermoplastic polymers were s substituted for the polypropylene and embossing conditions were correspondingly changed to allow processin~ of the polymers. The polymers, processing conditions, and the roll covers used to p~epared the embossed films are s--mm~rized in Table 1.
All films were pre,()ared using an embossing roll having a square lattice array of square posts (EB-2).

Table 1 Thermoplastic Polymer/Operating Conditions 1s Expl Polymer ChillExtruder Chill Embossing Line RollOperating Roll Roll Speed CoverTemp(~C) Temp(~C) Temp(~C) (m/min) 10 SurlynTM RC-1 225 7 54 1.5 11 Nylon RC-4 254 18 38 1.5 6,9' 12HostalloylM RC-1 305 18 38 0.6 13 PVC2 RC-4 170 16 38 0.6 1. Vydyne, available from Monsanto, St. Louis, MO.
2. Apex Telcar, available from Teknor Apex Co., Pawtucket, RI.

:[n Examples 10 and 12, the face ofthe film in contact with the chill roll bore microaberations consisting of a plurality of microprotrusions corresponding to inverted replicas of the surface pores of the foam chill roll cover. In Examples 1 1 and 13, the face of the film in contact with the chill roll bore microaberationscon~icting of a pattern of protruding cube corners.

CA 02234l~4 l998-04-06 E~cample 14 A microstructured polymeric substrate was prepared by the following procedure.
One end of a piece of 3MO Optical ~ ighting Film #2300 Acrylic (available from 3M, St. Paul, ~), app~o~ çly 90 cm X 10 cm, was secured, grooved face down, to a bench top with mq~in~ tape. The 3MO Optical T ighting Film has a plurality of sul~sl~ iAlly 90~ inr.luded angle ridges. The d~pres~;ons in the surface of the film are about 0.18 mm in depth. The unsecured end of the film was grasped in a manner such that a tear could be initiated in a grove appl o~ ,alely 2 cm from 0 the edge of the film and the film torn along its length. The film was torn at an angle of between appro~ alely 15-30~ from the holizonlal to produce a clean, straight edge having a substantially constant acute angle along one piece of the film and a complementary obtuse angle on the edge of the ~djacçnt piece of film. Strips produced in this manner were cut into app~oxilnately 6.5 cm lengths (herein after referred to as "master elemçnts") and used to assemble a master 112, a portion of the cross-section of which is illustrated in Fig. 16, in the following manner:
The grooved faces 10S, 106 of two master elements were nested together so that the acute tear angle edge 100 of one element (B in Fig. 16) extended beyondthe obtuse tear angle edge 101 ofthe second element (A in Fig. 16) by four ridges.
The smooth face 102 of a third master element (C in Fig. 16) was then placed against the smooth face 103 of the second master element (B) with the acute tearangle edges 100, 104 aligned. The grooved face 108 of a fourth master element (Din Fig. 16) was then nested with the grooved face 107 ofthe third master elem~nt(C) such that the obtuse angle tear edge 109 was indexed four groves below the 2~ acute tear angle edge 104 of the third element (C) and aligned with the obtuse tear angle edge 101 ofthe first master element (A). The st~cl~ing pattern (ABCDABCD... ) was repeated until a master, appro~hl~lely 1.2 cm X 6.5 cm was assembled. The total assembly was clamped together using a number of binder clips (5/8 inch capacity binder clip No. 100500 distributed by IDL Corp., Carlstadt, NJ).
A master mold ofthe master 112 was prepared according to the following steps:

a) Forcing a vinyl siloxane dental hl~pl~ssion material (3M
ExpressO, available from 3M, St Paul, MN) into the contol~red edge ofthe master with the m~n~lf~ct~-re's supplied application device, being careful to avoid enl.~ l of air bubbles between the s i,.. pr~s~ion material and the master;
b) CG~ ;n;n~ a pool of the dental il~press;on material on a glass plate between two ~lllminllm spacer bars (approxh~dlely 0 32 cm X
1 25 cm X 2 cm) positioned apploAh..dlely 2 5 cm apart;
c) Centering the master over the spacer bars such that each end 0 of the master ove-lapped each spacer bar appl o~ ately 0 5 cm andforcing the ;-~ css;on filled face of the master into the pool of ;.l")l~ss;on material until the h~p~ession filled edge ofthe master contacted the spacer bars;
d) Positioning two additional ~lumin~lm bars (approximately 0 6 cm X 0 6 cm X l0 cm) in the hl-p-ess;on material pool such that these bars contacted the ends of the spacer bars, thereby forming a co-llaill,..ent well for the i~prcssion material;
e) Allowing the in~pl ession material to cure;
f) Removing the master from the cured ;...plession material and trimming the ends of the cured mold to provide an appro~ ately 2 5 cm long mold of the master; and g) Securing end dams to the trimmed mold to provide a well for subsequent molding of polymeric materials in the mold Microstructured polymeric substrates were prepared by filing the master 2s mold with a vinyl plastisol (#D 1902-50 Black, available from Plast-O-Meric, Inc, W~ukech~ WI) and curing the plastisol in a cirClll~tine air oven at 204~C (400~F) for 15 minutes The cured plastisol was demolded to produce a flexible, compliantpolymeric substrate (50 durometer) having a plurality of grooved ridges The grooves ("microaberations") in the ridges were replicas of the grooves 111 in the sidewalls ofthe grooved ridges 110 of master 112 (and inverted replicas ofthe ofthe continuous protrusions on the sides of the depressions in the master mold) Example 15 Microstructured polymeric substrates having a plurality of grooved ridges were prtpaled from the master mold of Example 14, subst~nti~lly following the s procedure of Example 14, except that a firmer vinyl plastisol (#D1902-78 White, available from Plast-O-Meric, Inc.) was used to form the polymeric substrates (78 durometer).
All publications and patent applications in this specification are indicative ofthe level of ordinary skill in the art to which this invention pertains.
0 The invention has been described with reference to various specific and p~ ed embodiments and techniques However, it should be understood that many variations and modifications may be made while lelnAit)il~ within the spirit and scope of the invention.

Claims (10)

1) A method of producing a polymeric substrate comprising:
contacting a polymeric material in a flowable state with a resilient surface and an embossing surface to produce a microstructured polymeric substrate;
the resilient surface comprising a plurality of first microaberrations and the embossing surface comprising a plurality of embossing elements projecting therefrom;
wherein the microstructured polymeric substrate comprises a plurality of hollow projecting elements comprising an outer surface, the outer surface comprising a plurality of second microaberrations which are inverted replicas of the first microaberrations.
2) The method of claim 1 wherein the polymeric material comprises a thermoplastic polymer which comprises a polyolefin, a polyamide, polyvinyl chloride, a polyester or an olefin copolymer.
3) The method of claim 1 wherein the resilient surface comprises a polymeric foam or a nonporous flexible polymeric material.
4) The method of claim 3 wherein the resilient surface comprises a nonporous flexible polymeric material comprising a plurality of rigid microparticles embedded therein.
5) A method of producing a polymeric substrate comprising:
contacting a polymeric material in a flowable state with a resilient surface to produce a microstructured polymeric substrate;
the resilient surface comprising a plurality of undercut-shaped microdepressions;

wherein the microstructured polymeric substrate comprises a plurality of undercut-shaped microprotrusions which are inverted replicas of the microdepressions.
6) A polymeric substrate formed by a process comprising:
contacting a polymeric material in a flowable state with a resilient surface, the resilient surface comprising a plurality of first microaberrations;
wherein a microstructured polymeric substrate is formed, the microstructured polymeric substrate comprising a plurality of second microaberrations which are inverted replicas of the first microaberrations.
7) A polymeric substrate of unitary construction comprising a plurality of undercut-shaped solid microprotrusions.
8) The polymeric substrate of claim 7 further comprising a plurality of projecting elements comprising an outer surface, the outer surface comprising a plurality of the microprotrusions.
9) A polymeric substrate comprising a plurality of projecting elements comprising an outer surface which comprises sidewalls, said sidewalls comprising a plurality of solid microprotrusions, said microprotrusions having a width of about 10µm to about 400µm and a height of about 10µm to about 400µm.
10) The polymeric substrate of claim 9 wherein the projecting elements comprise a sidewall having a draft of no more than about 30°.
CA 2234154 1995-10-12 1996-09-16 Microstructured polymeric substrate Abandoned CA2234154A1 (en)

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