CA1247423A - Retroreflective sheeting and methods for making same - Google Patents
Retroreflective sheeting and methods for making sameInfo
- Publication number
- CA1247423A CA1247423A CA000463618A CA463618A CA1247423A CA 1247423 A CA1247423 A CA 1247423A CA 000463618 A CA000463618 A CA 000463618A CA 463618 A CA463618 A CA 463618A CA 1247423 A CA1247423 A CA 1247423A
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Abstract
ABSTRACT OF THE DISCLOSURE
A retroreflective relatively flexible laminate sheet construction has a thermoplastic web with a smooth light-receiving first side and a second side coextensive with said first side. A retroreflective pattern is formed on the second side. A slurry of granular material is deposited on the second side to cover selected portions of the formed pattern with remaining portions of the formed pattern devoid of the granular material, and said slurry is dried or cured to produce a well-defined pattern. A layer of backcoating material is deposited on the second side to overlay the granular material, the backcoating material contacting the thermoplastic web where no granular material has been deposited, thereby encapsulating the granular material between the second side and the backcoating layer. An added, outer layer provides additional weather protection for the thermoplastic web. Methods are detailed to manufacture the laminate, and compositions Or backcoating mixtures also are disclosed.
A retroreflective relatively flexible laminate sheet construction has a thermoplastic web with a smooth light-receiving first side and a second side coextensive with said first side. A retroreflective pattern is formed on the second side. A slurry of granular material is deposited on the second side to cover selected portions of the formed pattern with remaining portions of the formed pattern devoid of the granular material, and said slurry is dried or cured to produce a well-defined pattern. A layer of backcoating material is deposited on the second side to overlay the granular material, the backcoating material contacting the thermoplastic web where no granular material has been deposited, thereby encapsulating the granular material between the second side and the backcoating layer. An added, outer layer provides additional weather protection for the thermoplastic web. Methods are detailed to manufacture the laminate, and compositions Or backcoating mixtures also are disclosed.
Description
~ETRORE~FL,ECTIVE SHEETING ~ND METHODS
FOF< MAKING SAME
. . .
P~CKGRO~ O7~ TH1~ rIoN
Re~rore~lective sheeting has particul~r use il~ making highwey ~igns, Ytre~t signs and the l;ke, and is now employed extensively. Tne ~edernl government h~
recognized two primary types ot retrore~lec~ive 6heeting~ glass ~ead snd cube-corner. Such approved sheeting materlals ar¢ tound in c specirlcation entitled FP-79nl published by the U.S. Depnrtment or Tr~nsportation, Federal ~Ighwny Adminlstrntion. Speclrication PP-7~ presently has been adopted as n purchaslng standard by many slate highway depar~rnents~ ~nd it sets forth certRln mlnlmum spccl~ic~tions whlch must be met by retror~rlective sheetlng o? the cube-corner ~ype. Includcd among the specified characteristics are those for r~lectivity, color, 10 flexibillty ot m~terial and resi~tnnce to cr~cking ~nd weatherlng.
Cub0-corner type reflector elements gener~lly provide a higher speeiric intensit~ at 0.2~ observation an~le ~nd oD entrQnce angle thàn do glass bead type re~lector elements, but, to applic~nts knowledge, no one successrully has ~urnished R
sheeting material in commerclal quant;tie~ which generally will meet the requirements ~or the Class IIJB sheeting set forth in the sforement;oned FP-7 speci~ication. Accordingly, the present invention seeks to provide a unique sheeting pr~duct which will SU~StElntiBIly meet such ~pecitied criter~a and wh;ch can be produced in ~ccordance with the novel methods disclosed herein in nn economjcal fashion and in commercilll quantitie~.
Retlore~iectivity is achieved by cube-corner type reîle~tol- elements primarily through the principle oî total internal re~lection. It i5 well known ~hat any sur~sce contact made by another material with the races o~ the ~ube-corner elements generally hss a deleterious cffect on ~he renect~veness of the reflector element.
However, when all of the element fa~es are metallized, or mirrored, -t~en, rsther than relying upon total internal rerlection, retroreflectl~n is achieved by specular retlection from the mirrored ~aces. Generally, metallizing w;ll provide a gr~yish or black coloration under certain daylight conditions vis-a-vis unmetallized cube~orner type elements.
The present inventlon relates generally to methods and appQratus ~or pr~ducing retrorenective sheeting conslructions ~nd, more particularly, to methods y~
flnd ll~)pllrntllS ~0~` producing a rlexlble lnminnto shceting constructlon ln~luding nn upper th~rmopInst;c shcct, ~he reverse o~ which is provided with n repe~t5n~, r~trorefl~ctine pattern of fine or precise detnil, ~ backcoatlng to protect the ~ormed pattern~ and a selectively npplied intermediate layer allowin~ bonding ot the b~ckcoating to overlay the formed pattern on the thermoplastic sheet wh51~
preserving and enhancing the re~rore~lective properties o~ both the forrned pnttern ~nd the l~min~ted sheet. More precisely, the present Invention 1~ applicable to the production of cube-corner type retrore~lective ~heeting laminates.
With;n the ar~ of desi~ning reflector~ ~nd retrorerlective mut~rial, the 10 terms "cube~orner" or "trihedral," or "tetrahedr~ re recogni~ed In ~he art as describin~ s~ructure or patterns consisting Or three rnutually perpendi~ular ~aces, not limi~ed to any partictIlar size or shnpe of ths faces, or the orIentation o~ the optical A%is of the cube-corner element E~ch or the cube~corner fAces can assurne A different 3ize nnd shApe relative to the other~, depending upon the angul~r reflective response charncteristics desired, and the cube rorming techniques employed.
Examples of prior cube-corner type refleetor~ m~y be found in V.8.
Patent No. 1,906,655, issued to Stimson, and U~S. P~tent No. 4,073,568, issued to ~. Stimson shows ~ renex light reflector including an obverse ~ace and a 20 reverse light-renec~ing face consisting of ~ plur~lity of cube-corner type renector elements with esch such element having three mutual]y perpendicular sur~ces adap~ed for total internal reflection ~f light impîn~in~ thereon frorn the obverse face ~ describes a cube~orner type reflector in the ~orm Or a rectangu~r par~llelpiped.
It long has been desired to obtain the bene~its of cube~orner rene~tlve properties in the form of nexible sheeting. As noted above; one ~dvantageous aspect of such ~heeting is in the manufacture o~ highway and street signs, markers and the like, where graphics are printed, psinted, silk-screened or otherwise applied to a highly reflective substrate mounted to a nat, stif~, supportive surface.
30 Flexible retroreflective sheeting, when used ~s such a substrate, e~n ~e stored and ship~>ed while wound onto rol~s, and can readily be cut or otherwlse ~ormed into the desired shape and size required for a particular application. The reflective nature o~ the sheeting allows such si~ns, markers, ~nd the like to retlect li~hS from a vehicle1s headli~hts, permltting the item to be réad by the driver, without requirlng a F~ermanent light source to illuminate the sign or merker.
7~
Production of such re~rorefloc~ive sheeting h~s been m~de pr~atlcable by nppnrntlls ~nd methods to torm preclss cube-corner patterns ~n gre~tly reduced sl~e~s on flexible thermoplnstic sheeRng. Desirably, such sheeting may then be assembled in the form of sel~-adhesive laminntes.
Others h~ve recognized the desireability ot produ¢ing retrore~lecti~e thermoplastic material in sheet rorm. Unlted States P~tents Nos. ~,31û,790,
FOF< MAKING SAME
. . .
P~CKGRO~ O7~ TH1~ rIoN
Re~rore~lective sheeting has particul~r use il~ making highwey ~igns, Ytre~t signs and the l;ke, and is now employed extensively. Tne ~edernl government h~
recognized two primary types ot retrore~lec~ive 6heeting~ glass ~ead snd cube-corner. Such approved sheeting materlals ar¢ tound in c specirlcation entitled FP-79nl published by the U.S. Depnrtment or Tr~nsportation, Federal ~Ighwny Adminlstrntion. Speclrication PP-7~ presently has been adopted as n purchaslng standard by many slate highway depar~rnents~ ~nd it sets forth certRln mlnlmum spccl~ic~tions whlch must be met by retror~rlective sheetlng o? the cube-corner ~ype. Includcd among the specified characteristics are those for r~lectivity, color, 10 flexibillty ot m~terial and resi~tnnce to cr~cking ~nd weatherlng.
Cub0-corner type reflector elements gener~lly provide a higher speeiric intensit~ at 0.2~ observation an~le ~nd oD entrQnce angle thàn do glass bead type re~lector elements, but, to applic~nts knowledge, no one successrully has ~urnished R
sheeting material in commerclal quant;tie~ which generally will meet the requirements ~or the Class IIJB sheeting set forth in the sforement;oned FP-7 speci~ication. Accordingly, the present invention seeks to provide a unique sheeting pr~duct which will SU~StElntiBIly meet such ~pecitied criter~a and wh;ch can be produced in ~ccordance with the novel methods disclosed herein in nn economjcal fashion and in commercilll quantitie~.
Retlore~iectivity is achieved by cube-corner type reîle~tol- elements primarily through the principle oî total internal re~lection. It i5 well known ~hat any sur~sce contact made by another material with the races o~ the ~ube-corner elements generally hss a deleterious cffect on ~he renect~veness of the reflector element.
However, when all of the element fa~es are metallized, or mirrored, -t~en, rsther than relying upon total internal rerlection, retroreflectl~n is achieved by specular retlection from the mirrored ~aces. Generally, metallizing w;ll provide a gr~yish or black coloration under certain daylight conditions vis-a-vis unmetallized cube~orner type elements.
The present inventlon relates generally to methods and appQratus ~or pr~ducing retrorenective sheeting conslructions ~nd, more particularly, to methods y~
flnd ll~)pllrntllS ~0~` producing a rlexlble lnminnto shceting constructlon ln~luding nn upper th~rmopInst;c shcct, ~he reverse o~ which is provided with n repe~t5n~, r~trorefl~ctine pattern of fine or precise detnil, ~ backcoatlng to protect the ~ormed pattern~ and a selectively npplied intermediate layer allowin~ bonding ot the b~ckcoating to overlay the formed pattern on the thermoplastic sheet wh51~
preserving and enhancing the re~rore~lective properties o~ both the forrned pnttern ~nd the l~min~ted sheet. More precisely, the present Invention 1~ applicable to the production of cube-corner type retrore~lective ~heeting laminates.
With;n the ar~ of desi~ning reflector~ ~nd retrorerlective mut~rial, the 10 terms "cube~orner" or "trihedral," or "tetrahedr~ re recogni~ed In ~he art as describin~ s~ructure or patterns consisting Or three rnutually perpendi~ular ~aces, not limi~ed to any partictIlar size or shnpe of ths faces, or the orIentation o~ the optical A%is of the cube-corner element E~ch or the cube~corner fAces can assurne A different 3ize nnd shApe relative to the other~, depending upon the angul~r reflective response charncteristics desired, and the cube rorming techniques employed.
Examples of prior cube-corner type refleetor~ m~y be found in V.8.
Patent No. 1,906,655, issued to Stimson, and U~S. P~tent No. 4,073,568, issued to ~. Stimson shows ~ renex light reflector including an obverse ~ace and a 20 reverse light-renec~ing face consisting of ~ plur~lity of cube-corner type renector elements with esch such element having three mutual]y perpendicular sur~ces adap~ed for total internal reflection ~f light impîn~in~ thereon frorn the obverse face ~ describes a cube~orner type reflector in the ~orm Or a rectangu~r par~llelpiped.
It long has been desired to obtain the bene~its of cube~orner rene~tlve properties in the form of nexible sheeting. As noted above; one ~dvantageous aspect of such ~heeting is in the manufacture o~ highway and street signs, markers and the like, where graphics are printed, psinted, silk-screened or otherwise applied to a highly reflective substrate mounted to a nat, stif~, supportive surface.
30 Flexible retroreflective sheeting, when used ~s such a substrate, e~n ~e stored and ship~>ed while wound onto rol~s, and can readily be cut or otherwlse ~ormed into the desired shape and size required for a particular application. The reflective nature o~ the sheeting allows such si~ns, markers, ~nd the like to retlect li~hS from a vehicle1s headli~hts, permltting the item to be réad by the driver, without requirlng a F~ermanent light source to illuminate the sign or merker.
7~
Production of such re~rorefloc~ive sheeting h~s been m~de pr~atlcable by nppnrntlls ~nd methods to torm preclss cube-corner patterns ~n gre~tly reduced sl~e~s on flexible thermoplnstic sheeRng. Desirably, such sheeting may then be assembled in the form of sel~-adhesive laminntes.
Others h~ve recognized the desireability ot produ¢ing retrore~lecti~e thermoplastic material in sheet rorm. Unlted States P~tents Nos. ~,31û,790,
2,380"1~7, and 2,481,757, grRnted to Junç!ersenl, descri~e ~nd te~ch thc shortcomings ot previously known re~lectors msnutactured ~rom gless, and the advnntRges inherent in providing a reflective mRteri~l in a less rrngile and more ~lexible sheet ~orm.
While so suggesting, it is no~ known if ~;en in tact ever commerclali~ed any procluct disclosed ln such pRtentS-In U.S. Pntents Nos. 4,244,683 and 4,332,847 issued to ~ the desirnbility ot manufaaturlng cube-corner retrore~le¢tive sheeting In a continuous, non-StOp process is presented, but the approach selected by Rowland i8 e ~emi-continuous proces~s (Rowland 683, column 2, lines 18 - 38~, presum~bly so-calledbecause the process requires frequent repositioning o~ th~ moldJng p~tes.
In United States Patent No. 3,187,068, lssued to ~, continuous production ot retlective sheeting is disclose~, utiliz(ng encapsulated glass rnicrospheres RS the reflecting medlum. ~i~,~ descrlbes th0 application of 2 0 a pressure-sc~ivR~ed adhesive layer to such sheeting to enable attschment o~
sheeting segrnents to selected sur~aces.
In United Ststes Patent No. 3,649,352, issued to ~ ~ beaded sheeting construction is described, portlons of which becorne reflective when he~ted, snd which includes a pressure-activated adhesive layer allowlng ~ttechment Or the sheeting construction to other articles.
~L~ 2,407,680 teach the utlliz~tion of glass microspheres or besds included as the reflective elements in flexible sheet torms; Tung~ et Al., in United States Patent ~o. 4,367,920, also describes a lamir!ated sheet construction using glass microspheres as the reflective e1ernents.
A common prob]en~ in the construction ot re~lective 1sminate sheetlng Ig to rind means to bond the ~amins firmly together in a way which preserves the reguired retrorenective qualities ot the retlective elements selected ~or use. An exsmple of prior e~forts to solve this problem with respect to gl~ mlcrospheres may be seen in United States Patent No. ~,190,~78, issued lo Mcl~enzle, whereln ~
cover sheet or tilm ls s~ecured over exposed gl~ss micr~spheres by use ot die ~ ~ .
elements which torce a por~ion ot the materlal In which the gl~ss microspheres nre ~4--f '7~
embe(lded into contnct wi~h the eover shcct. The dia elernents thus areate ~ grid pnt~ern on the resultin~ shceting construction, wi~h eflch grid forming ~ 6eparRte cell. Withln ench cell, nn nir space is m~int~ined between the mlcrosphere% and ~he cover sheet, nnd incident light tr~verses the cover sheet and the alr sp~ce to b~
retrorenected by the embedded m;crospheres.
Holmen et ~1 U.S. Pa~ent No. 3,924,9~g, t~ach a cube~orner type upper rigid sheet hnving upstflndin~ wnlls, or septn, inlegr~lly ~ormed ~s p~rt ot the cube pattern. Ille septa extend to form e regular geometric pattern o~ Indiv1du~1 cell~, with the sept~ extending ~t least as rar rrom t'he upper sheet as the cube-corner 10 ele~ents. A particulnte packing mny be used to ~ill each o~ the cells, ~nd a backing 6hect is then ~ttached to the rear of the upper sheetg wlth the ~epts sorving as the nttachment sites. ~L~_ use rel~tively lnr~e cube~orner elements fnshioned as rigid sections bound to Q tlsxible baek, and h~s limited flexibility In use.
In ~, U.S. Patent No. 4,025,l59, the cellular concept i~ desoribed with respect to cube-corner type retrore~lective sheetin~, through use oi~ dies to force a carrier film into contact with the reverse side of the cube-corner sheeting.
The carrier filrn must then be cured with rndiation to bind it to the cube-corner sheeting snd, as in ~~, the resulting cells include sn Qirspace extending 20 between the c~rrier ~ilm snd the reverse side o~ the cube-corner she~t. The ~ir cell structure apparently wns intended to provide a hermetically sealsd cell, avoldin~
the need for metalizing the cube-corner elements, ~nd providing ~n air/thel-moplastic interr~ce to enhance retroreîlection.
None Or the roregoin~ teach the assembly o~ molded or embossed ~ube corner type retroreflective sheeting into sel~-adhesive laminates whlch protect and enhance the renective properties of the sheeting without requir;ng the use of die~
or o~ integrally-molded septa or walls ineluded 85 part of the eube p~ttern.
Purther, none o~ the roregoing permits the material to bene~it from enc~psulated seclions or cube~orner e]ements while enhancing and substantially meeting the 30 requjrements speciried in the ~forementioned DOT FP~7~ Speciric~tion.
~RIEP DESCRIPTION O~ THE INVENTION
,, ~
A thermoplastio sheet or web ;s provided on ~ts reverse s1de with Q
retrorerlective cube~orner type p~ttern. A thin leyer o~ n 11quld vehicle or solvent containing hydrophobic gr~nul~r rn~terial ~such ns gilic~ tre~ted w1th sllnnes~ it~- -deposited on the reverse side ot the web, n~ by screen printing, in n pnttorn leavln~
_5_ '7~
selQctad s~Ltes devo-Ld oE grilnul~r materLal.. The weh Is then drled to drLve oEE the solvent and, thereafterJ a water-based backcoating i9 app].ied over the grflllular material pattern, with portions of the backcoating being in direct contact with the thermoplastic web at those sites on the web devoid of granular material. Thereafter, the backcoating is dried or cured, and a layer of adhesive such as pressure-sensitive or heat-activated adhesive is applied thereto. This procedure thus enables the assembly of patterned web material into laminates which include an activated adhesive layer while protecting the retroref].ective properties of the precise:Ly formed cube-corner pattern.
~ ore particularly, one aspect of the invention pertains to a flexlbleretroreflective cube corner type laminate sheet construction including a thermoplastic web w:Lth a l:Lght-receiving and transmitting first side and a second side coextensive with the first side, and a cube corner type retro-reflective pattern formed on at least a portion of the second side. The construction comprises a layer of hydrophoblc granular material deposited on the second side to cover selected portions of the formed cube corner retroreflective pattern with remaining portions of the second side devoid of said hydrophobic granular material. A layer of backcoating material is deposited on the second side to substantially completely overlay the hydro-phobic granular material without disturbing the pattern formed by the granular material. The backcoating material substantially fully contacts the portlons of the second side devoid of the granular material and is fixedly secured thereto, thereby ~ncapsulating the hydrophobic granular material between the second side and the backcoating layer. The particle si~e of the hydrophobic granular material is such that the area in which it is deposited will be effectively impervious to the backcoating material whereby the backcoating material is unable to penetrate the granular material and interact with the second side except in the area devoid of the granular material.
Another aspect of the invention comprehends a method for producing a cube corner type retroreflective laminate sheet construction comprising the steps of applying to a web of thermoplastic material having a retro-reflective cube corner formed pattern on at least a portion of one side a '7~
laya~ of hydl~ol-llol-l.c grfln~ll.nr ma~arl.nl. do~)091.t:ecl ~so a'J to Eorm a reg~.l.l..lr nnd ~al)en~l.nu nrrny Oll ~he rc~rorcE:I.ec~:Lve pattern and ~ormLng, as pnrt oE
thc nrray, n pl~lrnl:Lty o~ paths on the one .s:Lde clevold oE the hydrophobic grannlar mflter:Lal. A layer o~ backcoati.ng materi.al is applled to overlay the hydrophobic granular mater:Lal and to flll the paths, and i5 adhered to encapsulate the hydrophobic granular material between the formed side and the backcoating materlal. The particle 9ize of ths hydrophobic granular material is selected so that the area in whi.ch it i9 deposited will be effectlvely lmpervlous to the backcoating material whereby the backcoating material ls unable to penetrate the granular material and lnteract wlth the second slde except l.n the area devold of the granular materlal.
In a preferred embod.lment, an outer protectlve layer of thermoplastlc mater:Lal, used to provide additional weather resistant properties, is secured to the thermoplastic web on the side opposlte from that upon which the retro-reflective pattern is formed during or before the cube formlng process.
The completed lamlnate is then CutJ trimmed, or otherwise shaped for application to supporting surfaces, such as street or highway signs, and graphics or other indicia may thereafter be painted, printed, silk-screened, or otherwise affixed to the uppermost surface of the laminate, thus producing a readily and easily constructed highly retroreflective finished product.
These and further aspects of the present invention will become more apparent upon consideration of the accompanying drawings, wherein:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an enlarged perspective and somewhat schematic view of one preferred aspect of the retroreflective sheeting of the present invention as a completed construction;
FIG. 2 is a view along line 2-2 of Eig. 1;
-6a-B
Pla. 3 is n grcntly onl~lrged pl~ln vlew Illustr~ting a secllon ot the ~ormcd surfnce o~ reflectlve sheeting comprislng on~ aspect of ~he present inventlon;
~ la. 4 is a somewhnt schemntic Rnd symbolic vlew of the proaesses and rnnchinery utilized in n pre?erred Aspect ot the present inven~ion;
~ IG. 5 is fl plnn vlew o~ one form of screen p~ttern used to apply th~
hydrophobic gr~nul~r leyer of the present invention;
PIG. 6 is an enlnrged view, In partial detail, of an indivlduQI cell o~ ~he sheeling ot the present invention; and PIG. 7 is an enlarged perspectiv~ v~ew illustr~tln~ a ~econd preferred 10 embodiment of the retroreflective sheetin~ ot the present Invention.
D~rAll,ED_DESCRlPTlO~INGS
Reterring now to Pig. 3, the numeral 10 indicates generally B segment o~
cube-corner type retrorerlective thermopl~ic web used in forming the lamina~e or the present inventlon. As seen In Pig. 3, there is ~epicted the rear su~f~c~ ot a portion or (lexible retrorerleclive sheeting 12 ~ashioned rrom transp~rent thermopla5~jc ma~erial in web form which hQs formed thereon, preferRbly by embossing, a retrorenective ~nd repeating pRtterl of cube~orner re~lector element~
characterjzed by cu~e faces 14, 16 ~nd 18. In ~ preferred aspect of suc~ sh0~ting, sheet 1~ is formed from an impact-modified acrylic material having t~Y inhibitors or 20 absorbers ndded thereto, Qnd which, prior to embossing, had par~llel ~ront ~nd bnck surf~ces ~nd W1~5 initially on the order Or ~bout O.OOB inches thick. One such materi~l is known ns Plexiglas DR, sold by the ~ohm and HnAs Comp~ny.
The cube-corner pattern formed on sheeting 12 is formed in ~n optically precise, Iinely~etailed pattern. Por examplet as seen in Pig. ~, the depth to whlch the cube~orner pattern is embossed onto sheet 12 may be o~ the order or ~.OD338 inch, (dimension X~. As shown at dimension Y in Pig. 3, the cubes formed on sheet 12 may be spaced ap~rt by a distance on the order of about 0.0072 inch, ~r the depth as shown at X as set ~orth above~ While the cube pattern shown in ~lg. 1 i]lustrates cubes formed with their optical ~xes normal to the race Or sheet 12, it is 80 to be understood that other versions and p~tterns m~y also ~e utilized ~15 ~ormlng the retrore~ective web of the Inminnte of the presen~ invention.
~ e~errin~ now to Pig. 1, the numeral 20 indicstes gener~lly a roll ot retrorenectlve l~minate 22 manufactured In ~ccordance with prererred ~spec~s o~
the present InventlorI to be described hereinbelow. As hereln shown, Inmlnata 22 i~
rGlled onto Q core 24. A thermoplastic web 2~ h~ving a front or obvcrse ~urlrfl~o 28 , . .
'7~L~3 nnd ~ rcnr or roversc surtncc 30 upon which i~ embossed th0 cu~e-corner type retroretlective pnttern LLlustrated ln FLg. 3. Th~ thermop1astic web 26 may be on ~he ordcr or about 6 mils in thicknes~ (0.006 inch).
Bonded to the reverse surrsce 30 Or the thermoplasticw~b 26 i~
bsckcosting or ~ilm 32. In Q prererred sspect of the present inventlon, a hydrophobic granular silica materiRl 34 is Intetposed between th~ b~ckco~t tilm 32 and the reverse side 30 in ~ manner to be! Jescribed hereinbelow.
In sccorda.nce with a preterred embodiment of the pres~nt lnventlon, n layer ot adhesive 36 is bonded to a release sheet 38 in n prasently well-known 10 fnshic>n~ and is ~here~rter bonded to cured baokcost film 32 In order to proYld~ a tinished laminate 22 which includes a prcssure-6en~itive or heat-activated ~dhe~lve laycr 3~ upplied to sheeting 12 in a mBnn~r which preserves the retroretleetlv~
cluali~ics nnd properties ot the cube-corner pattern embossed thereon. The release sheet 38 is used to protect adhesive l~yer 36 until It is desired to npply l~minBte 2a to El given ~urf~ce.
Pig. 4 shows~ in schematic form, a preferred arrRngment ot equipment and sequence of operatlons to produce e retrorenectSve sheeting l~minnte ot the type shown ln ~ig. 3.
The applicat~on of adhesive directly to the reverse sid~ o~ Q CU~e-Corner 20 embossed thermopl~s~ic web 26 will cause ~n undesira~lo and unac~ceptable lo~s of retrorenectjye cap~bility. This ~rises from the contact ot the sdheQlve materi~l with the reverse side o~ embossed thermoplastic~ web 26, ~ ~ ~ the ~ ng o~ the "valleys rormed by the embossed pnttern Qnd the subseguent inter~ace formed between substances that ~re too similar in refractive indices to produce adequ~te retroreflection, so the transparent film can no longer utillze the phenomenon o~
total internQI renection to efticiently effect retroretlection or lJght. Tb solve thls problem, A sub~tantial portion of the cube~orner pattern either must be hermetjcQLly sealed with an air space ~etween the bsck wall ~nd the oube-corner elements, or the cube~orner elements must be backed in e way whirh would 30 preserve the rstrorenectlve properties o~ the ~ormed web while providing slte~ ror rirm ~lt~chment of an adhesive Isyer (or other adhesive m~terisl). Without such protection, and without such atteching sites, the use of, ~nd e~fectiveness o~ a retrore~lective embossed web is seriously compromlsed and curtslled.
Vnexpectedly, use of hydrophobio granular materials has been ~ound to artord such protection or optical properties. Among such materl~l~ aro xylen~ted~
glass particles, powdcred silicone rubber, end silane-tre~ted 8111c~.
.
.~24'~
As part Or the present inven~ion, It hns b en found thnt Q hydrophobicsilic~ mixture consisting principAlly of nmorphous silic~ treated w5th sllanes, when used to rill the v~lleys formed by the emboss¢d pnttern, preserve6 the retroreflective properties of the ~ormed pattern for mo t practical purposes~ Agaln, it is not known precisely why this etfect obtsins: it has been theorl~ed thet the point contact of gr~nules with the reverse ~ace of the ernbossed thermoplasti~ web ncts to preserve the retrore~lective properties ot the psttern, perhnps by preservlng A su~ticient ~ir interfnce with the reverse side ot the cube-corner pattern.
However, the present invention obtains excellent resu~ts even where the primary 10 silicn psrticlea used sre 6ignificQntly smaller thaIl~ for example, the pnrticle~
discussed in prior ~rt patents such flS ~ V~. Patent No. 3,924,929.
Use of such sllica ofrers advAntages such ns low prlce, avaIlAbJllty, ~nd ease nnd precision of forrnulation. It further provides unlque color a~d ref~ectlve chnrRcteristics to the tilm which improves the appenrance of the rilm even relative to the glass bead types heretofore commonl~ used.
As discussed hereinRbove with respect to the ~ et al reference, others h~ve nttempted to solve the problem-of loss of renectivlty by provIding Ups~andirlg walls or septn as pnrt of the rigid molded tront fscs pstîern, with the septa rorming indi~idual pockets for the npplication o~ granul~r ~ompound3 h~ving 20 pnrticle size~ far in excess of the silica particles used in the present inventlon.
The disadv~ntages to such nn approach, pnrticularly with respect to the cube~orner type embossed pattern utilized in the present invention are manirest. U~e o~ ri~id septa limit~ the size and shnpe o~ the cell. A separate mold must be formed for each type of retroreflective sheeting reguiring ~ ~ell size other th~n thQt formed in the origin~l mold. What is mennt by tne terrn "cell si~e" i~ the area bounded by or closed off by the walls to torm e single pocket ~or the grsnular backing material.
Formation o~ such septa in ~ relatively r;gid mold p~ttern m~nutactured to ~s fine ~nd precise a degree ot detMil as that shown in the present SnventSon al~o mny cause problems with respect to stripping the formed thermoplnstic web ~rom 30 the forming tool. This rnay particulsrly be a problem where the sept~ or wsll~
extend inwardly into the mold to n distAnce grenter than the depth oî the cube-corner pattern.
A preterred embodiment ot the present Invention includes the mixing of hydrophobic silic~ mixtur~e using hydrophobic sill~n, orgnn5c solvents, and thickener~, ~nd the app]lcat5On or this mixture~ whlle In n Ik1~id torm, to the re~/erYe YIde Or~
~he tormed therrnoplns~ic web 5n a desired pnttern One ndvantnge ot the pre~ont --9_ '7~
proccss nnd pr~uct is thQt thc p-lttern CAn ¢onvcnicntly be ch~nged to eftect chnng~s in rcrtcctive c~pabili~y oi~ ~hQ ~ilm, without changln~ the tov~5 u5ed In torming the embossed wcb. Thereatter, the partlQlIy coated or imprinted thermoplastic web is pnssed through a drylng oven which drives off the solvents used to torm thc mixture, thereby drying the p~ttern on the thermopl~s~5c ~heet. l'hepattern in which the silica is applied to th~ thermoplasiic web leave~ selccted por~ions or sites on the formed ~ace o~ the thermoplastic web devoid ot s~lica.
Re~errln~ now to Fig. 5, the numer~l 40 indicates ~enerally suoh fl selected p~ttern. Each runner or p~th 42 represents ~n ~rea on the reYerse surrace 10 ol therrnoplastic web 26 where no silica h~s been d~j~osited. E~ch ~quar~ or di~mond~h~ped nrea 44 represents ~n nren on the sur~Aoe Or thermopl~stic w~b 26 onto which tho slllos mixturc has been deposited.
As seen In Pig. 6, the nctual percentage of are~ covered by the ~ilic~
mixture is determined by the thicl<nes~ or width o~ each runner or path 4a, and the pa~tern selected lor deposition ol the silica, with the cell ~14 h~vln~ an are~
~ounded by the runners 42, and rully avail~ble ~or the reception and retrorenectlon o~ incident light by the embossed retroreflective pattern~ shown partl~lly ~t 4~.
Re~errlng now to Pig. 4"t may be seen that thermop1asti¢ web ~6 may be drawn directly ~rom ~n associS~ted rorming machine (not herein speciJ~ie~lly ~hown~
20 in a continuous process, or m~y be drawn ~rom a separ~te suwly reel onto which the embossed web 2~ has been wound (not herein specirical1y shown~ deslred, web 26 may be supported by a backing sheet (not hereln specilically shown3 coextensive with obverse face 28, leaving reverse sur-ace 30 exposed.
lt ~hould be noted ~hat re~erence to web 26 E1150 ~ncludes re~erence to a lsmin~te rormed by web 26 and a backing sheet such as described hereinabovc.
Web 26 is drRwn by, for example, powered rollers ~not herein 6peclfically shown), to ~ilicQ mixture ~pplication st~tion 48. ~ herein diagrAmmaticalty shown, a pre~erred me~ns and method Or applying the sill~a mJxture to web 26 may be accompllshed through use ot a screen-printing cylinder 50 which hQs moun~ed about 30 ~he outer periphery thereor, a metal screen lormed to provlde the shape or pattern to which it is desired to apply the ~llica mlxture~ Th~ mixtura Ts ~orced under pre~we from the interior of screen-printing drum 50 onto the reverse side 30 of the thermopla.stic web 26,~ As herein shown, the web 26 is directed by idler rol-ler 52 ~o pass bel:ween the screen-printing drum 50 and a backin~ roller 54, A prererred ~orm of the ~pp~ratus utllized to Apply th~ silica mlxturs et application station 48 consists of ~ drum prlnter manufacturod by Stork BrabAnt BY
-lU-.a~7~
o ~ lloxoc~r, llollnn(i, ot the lype hnvlnE n drum wlth clcclro-~ormed mcsh scrcer~s ovcr which n ~ oto-resist p~tSern ~such ~s used ~OI oonventionnt silk screen) mQy be moun~ecI, with n screcn pattern providing a dinmond cell ~Ize in the range of trom nbout 0.096 inch to 0.300 inch, nnd ~ runner or cell wall thIckness of trom flbout 0.010 inch to ~bout 0.050 inch. Vnriations Ih the shnpe or the cell~ ttern repeQt ot She cellc, nnd thickness of the runnerY msy be accolnplished by changing the printing screen used on screen-printing drum 50. Also, the con~t~nt wldth o~ theweb mny be of various sizes, and the printing 6creens used will be o~ ~ compntlble width.
ln its preferred rorm~ the silica mixture Is mede ~rom a. hydrophobi¢
silicn such ~s that manutactured by the Pigments Division ot De~uss~, ot Prnnk~urt, West Germnny, under the tr~de desi~nnti~n ~ipernat DIO~ A prererred composltlon ot ~he mixtur¢ includes hydrophobic silic~ in Q mixture contàining npproxlm~lely g8 perccn~ sllnne-trested silicon dioxide (SiO2~; 0.8 percen~ sodium oxide (N~20), ànd 0.8 percent o~ sulfur trioxide (SO~ non-polar nliphatic hydrocarbon soIvent c~rrjer; R polar solventj And, where desired or required, ~ thickening agent. One aliph~tic non-polnr hydrocarbon solYent successfully used is low odor mlner~l ~pirlts~
and Q workable mixture hss been creQted through use o~ an orgsnic nlcohol, pre~erQbly butsnol, as the polar solvent mQterisI. ~ smect;te clay-b~sed thixotropic 20 thickener also m~y be used in vQrying amounts to produce a well^derined screen-prinled p~ttern or the silic~ slurry on the embossed thermopl~stic web.
In ~ts preferred embodiment, the primary pQrticle size of the slllcs is ~bout 18 nanometers, and the Qgglomerated particle sizc of the hydrophoblc ~51ics in its final form is about S microns. However, it will be understood th~t the only critic~l limitation on the p~rticle size Is such that the ares in which It ;s deposited will be 6ubst~ntiE~IIy impervious to the backcoQting ma~eri~l 32, whereby the bsckcosting rn~teri~l ;s unable to penetrate the hydrophobic sillc~ and intersct with the cu~e-corner psttern except In those ~reas devoid ot the silic~
l~e p~rticular combinstion ot solvents and thickeners is import~nt to 30 sstistactory deposition and definition ot the silica in Q precise 6nd accurst~ pAttern.
Screen printing of p~rticulste material commonly requlr~s use ot resins or otherbinder5 to hold the deposited ~ar~icles in place. A resln or blnder c~nnot however be used in this instance because o~ the adverse eî~ect on renectlvlty ot the webbecsuse ot retrsctive Index Ylmil~rIties.
Another importnnt consider~tion 15 the rheology, or nOw chQrQct~rlstlcs o~
the silicn slurry ns It iB ~orced ~hrough thc printlng 6creen. The 61urry must ~,. ..
'74~'~
"rolnx," or thin ns lt is ~orce~l throllgh the screen npertures, ~nd therentter regain ulfricicnt viscoslty to rctaln a wel)-detined pattern with good leve!lng qll~lities and appenrance cha-acteristics. Yet another consider~tion 1~ use Or n ~olvent vehlcle which obtAins the a~orcmentioned qualities without ~ttacking or degrsding the thermoplastic web upon which the retroreflective pattern it ~ormed.
Use or pol~r solvents, such as butanol, enables the slurry to malntaln an increflsed concentrfltion of solids (silics~. Such solvents, however, resct with the thermoplastic matelial used to form the web. Non-polar solvent~, su¢h n5 mlnerB
spirits, preserve the embossed web, yet do not sct to provide n shtls~ctory slllca 10 p~ttern l`herefore Q blend of polnr snd non-polnr solvents has been round to be use~ul in carrying enough solids without degrading rerlectivity or degrading the web.
Preferably, the hydrophobic silicA is present in proportions rHnging rrom about t5 percent to about 35 percent by weight, the non-po2ar solvent carrler ls present in amounts ranging ~rom about 40 percent to about 70 percènt, the poIar solvent i5 present in amounts ranging from about 10 percent to about 30 percent, and the thickening ~gent may be present in arnounts from about 2 percent to About 8 percent. One preferred formulation of the silica mi~ture includes 20 percent ~y weight Sipernat D10 hydrophobic silica, 56 percent mineral SpilitS, 20 percent butanol, and 4 percent thickener. It has been found th~t such proportions preserve 20 the web while providing a useful silica p~ttern.
A~te~ application of the s51ica mixture, web 2~ is passed through ~
he~ting oven 56 where the resulting silic~ pattern is heated to drive off the orgnnic solvents without heQting web 26 to the ~oint where heat distortion o~ the cube-corner elements o~ the l~minate will occur.
Arter drying, the silicn is mechanically held to the cube~orner element~
on the reverse face 30 o~ web 26 by, it is believed, electroststic force~ and physical inter-engsgement Or the silica j~rticle~ themselves.
Thu~, RS web 26 exlts rnixture application stRtiOn 48~ It has t~ken on the rorm o~ n ~irst modified laminate 58, ~ ~, a web 26 h~ving cube~orner element3 30 with s precisly îormed pattern of silic~ mixture screened thereon over n pc~rtion Or the elements, wlth an uncovered portion Or the cube~orner elements stll~ exposed.
As modi~ied laminate 58 exits drying oven 5B, it t~kes on a second modi~led laminate construction 60 wherein the solvents present in the sillca mixture hnva been drlven o~ ~nd the silica itselr has remained dried into it~ ~raened-on p~ttern.
The second modi~ied laminnte 60 then enters n btlckcoatln~ apptl~ntion s~a~ion B2. The appllcatlon of n water-bnsed ~ckconting nccompllshw .qevor~l rcslllt~q. ~irst, tho~c nrons onto whlch no sillc~ has boen screcned or deposlted witlallow direc~ conlnct between the bnckco~ting nnd the revelse ~Ide 30 or the embosscd or otherwise ~ormed thermoplastic web a6, thus "wetting" web 2~ wlth the liquid backcoa~ing mix~ure. Second, a layer or b~ckcoating materi~l will oYerlay the silica pnttern formed on thermopl~stic web 26 ~nd, when applied etfecti-/ely, will not disturb or disrupt the printed or screened-on silic~ p~ttern. Third~ th~
backcoat;ng may then be dried and/or cured to provide a rirm ~tt~hment to thermopla5tjc web 26 to provide B flat, smooth ~nd integral surrace upon which further layers, such flg a l~yer or pressure-~ensitive or he~t-activ~ted adhesive m~y 10 be ef~ectively and conveniently applied, and to protectively cover or encapsulate the silica pattern. A surprising and unexpected result Is thQt the slllc~ prevent~
perrnefltlon by the liquid bnckcoating to the cube-corner i~ttern. As deYcribed nbove, such permention would adversely artect the reflectivlty of the rinal sssembled laminate.
Applicntion o~ the backcoating mix~ure to the second moditied laminata 60 msy be sccom~lished in a number o~ ways, such as by spraying, roller applicat;on, squeegeelng, or the like. The m~nner in which the bRckcoQt i~ appl;Qd will be determined by, inter ~ the precise formulation Or the backcoat and the pressure, or ~orc~, which can be withstood by the silica psttern aft~r i~ lu5 b~en 20 drie~.
Por purposes o~ illustration, a bsckcoating app~ication stat;on ~2 may be char~cterized fl~ having a supply header or tsnk 64 ~ommunicating with an flpplication means B6 which may ~e a nozzle or series of nozzles, or the 13ke. An implement such as a doctor bl~de 68 may be used to more unii~ormly spread the bnckcoating a~ter i~ has been applied without damaging the slllca pattern. A pl~ten 70 provides support ~or the second modified laminate 60 during application ot ths backcost .
A~ter application, the third modified Iflminate 72 enters drying oven 74i wherein the backcoat material is heat~ured, resulting in backcoating layer 32 as 30 shown in ~ig. 1.
Succes~tul use or fl backcorlting requires that the backcontlng ~ormulstion meet several p~srticu!Qrly important workln~ parRmeters. On~ ~s th~t the b~ckcoating have rlow charflcteristics such that ~he relatively narrow ancl 8hal10w runners formed by the silica pattern wlll be filled, while not dewetting or disturbing the dried ~llica p~tterri itselr. ~is me~r~ thflt the viscosity of the backco~ltln must be cnre~ully controlled to ~ssure thnt the bnckco~tlng chn be flppliod ~hilo 13~
'7~
cornplctely encnpsu~nt;ng wi~hout disturbing the sillc~ pnttern. Another chAr~c-~eristic Is that lhe b~ckco~ting cnnnot penetr~tQ or interRct with the npplied s(lica to reach the Inter~ace belween the sillc~ ~nd the cube-c~rner pnt~ern. Yet 8nother requirement is that the backcoatin~, when dried, hsve the reguired ~lexlbil5ty and toughness to withstand use in a laminate. Ideally, the b~ckcoflting ~hou~d also be or a color which enhances day~ime vislbility Or artlcles rnadé w3th ~uch l~minates.
Several preferred backcoatings have beerl utilized. ~ch may be characteri~ed generally as including a water-borne or w~ter-bssed polymerlc mixture or system, B whitening ~gent, Q defosmer, a thickener for use In ~d~ustlng the rin~l 10 viscosity~ and a pH-adJusting componont.
A ~irst prererred ~ormulation o~ n b~ckcoating i~ presented herewlth a~
Example 1-~ *
1. DP-101, a water-borne polymeric system consisting o~ about 34%
acrylic/urethane copolymer, 61% water and 5% coAlescent solvent, such a~ M-pyrol 6~.7% to 7~.7%
2. UCD-1D60Q, a pre~ispersed whitening agent (tltanium dioxide) containing about 72% solids 21.5% to ~3.5%
While so suggesting, it is no~ known if ~;en in tact ever commerclali~ed any procluct disclosed ln such pRtentS-In U.S. Pntents Nos. 4,244,683 and 4,332,847 issued to ~ the desirnbility ot manufaaturlng cube-corner retrore~le¢tive sheeting In a continuous, non-StOp process is presented, but the approach selected by Rowland i8 e ~emi-continuous proces~s (Rowland 683, column 2, lines 18 - 38~, presum~bly so-calledbecause the process requires frequent repositioning o~ th~ moldJng p~tes.
In United States Patent No. 3,187,068, lssued to ~, continuous production ot retlective sheeting is disclose~, utiliz(ng encapsulated glass rnicrospheres RS the reflecting medlum. ~i~,~ descrlbes th0 application of 2 0 a pressure-sc~ivR~ed adhesive layer to such sheeting to enable attschment o~
sheeting segrnents to selected sur~aces.
In United Ststes Patent No. 3,649,352, issued to ~ ~ beaded sheeting construction is described, portlons of which becorne reflective when he~ted, snd which includes a pressure-activated adhesive layer allowlng ~ttechment Or the sheeting construction to other articles.
~L~ 2,407,680 teach the utlliz~tion of glass microspheres or besds included as the reflective elements in flexible sheet torms; Tung~ et Al., in United States Patent ~o. 4,367,920, also describes a lamir!ated sheet construction using glass microspheres as the reflective e1ernents.
A common prob]en~ in the construction ot re~lective 1sminate sheetlng Ig to rind means to bond the ~amins firmly together in a way which preserves the reguired retrorenective qualities ot the retlective elements selected ~or use. An exsmple of prior e~forts to solve this problem with respect to gl~ mlcrospheres may be seen in United States Patent No. ~,190,~78, issued lo Mcl~enzle, whereln ~
cover sheet or tilm ls s~ecured over exposed gl~ss micr~spheres by use ot die ~ ~ .
elements which torce a por~ion ot the materlal In which the gl~ss microspheres nre ~4--f '7~
embe(lded into contnct wi~h the eover shcct. The dia elernents thus areate ~ grid pnt~ern on the resultin~ shceting construction, wi~h eflch grid forming ~ 6eparRte cell. Withln ench cell, nn nir space is m~int~ined between the mlcrosphere% and ~he cover sheet, nnd incident light tr~verses the cover sheet and the alr sp~ce to b~
retrorenected by the embedded m;crospheres.
Holmen et ~1 U.S. Pa~ent No. 3,924,9~g, t~ach a cube~orner type upper rigid sheet hnving upstflndin~ wnlls, or septn, inlegr~lly ~ormed ~s p~rt ot the cube pattern. Ille septa extend to form e regular geometric pattern o~ Indiv1du~1 cell~, with the sept~ extending ~t least as rar rrom t'he upper sheet as the cube-corner 10 ele~ents. A particulnte packing mny be used to ~ill each o~ the cells, ~nd a backing 6hect is then ~ttached to the rear of the upper sheetg wlth the ~epts sorving as the nttachment sites. ~L~_ use rel~tively lnr~e cube~orner elements fnshioned as rigid sections bound to Q tlsxible baek, and h~s limited flexibility In use.
In ~, U.S. Patent No. 4,025,l59, the cellular concept i~ desoribed with respect to cube-corner type retrore~lective sheetin~, through use oi~ dies to force a carrier film into contact with the reverse side of the cube-corner sheeting.
The carrier filrn must then be cured with rndiation to bind it to the cube-corner sheeting snd, as in ~~, the resulting cells include sn Qirspace extending 20 between the c~rrier ~ilm snd the reverse side o~ the cube-corner she~t. The ~ir cell structure apparently wns intended to provide a hermetically sealsd cell, avoldin~
the need for metalizing the cube-corner elements, ~nd providing ~n air/thel-moplastic interr~ce to enhance retroreîlection.
None Or the roregoin~ teach the assembly o~ molded or embossed ~ube corner type retroreflective sheeting into sel~-adhesive laminates whlch protect and enhance the renective properties of the sheeting without requir;ng the use of die~
or o~ integrally-molded septa or walls ineluded 85 part of the eube p~ttern.
Purther, none o~ the roregoing permits the material to bene~it from enc~psulated seclions or cube~orner e]ements while enhancing and substantially meeting the 30 requjrements speciried in the ~forementioned DOT FP~7~ Speciric~tion.
~RIEP DESCRIPTION O~ THE INVENTION
,, ~
A thermoplastio sheet or web ;s provided on ~ts reverse s1de with Q
retrorerlective cube~orner type p~ttern. A thin leyer o~ n 11quld vehicle or solvent containing hydrophobic gr~nul~r rn~terial ~such ns gilic~ tre~ted w1th sllnnes~ it~- -deposited on the reverse side ot the web, n~ by screen printing, in n pnttorn leavln~
_5_ '7~
selQctad s~Ltes devo-Ld oE grilnul~r materLal.. The weh Is then drled to drLve oEE the solvent and, thereafterJ a water-based backcoating i9 app].ied over the grflllular material pattern, with portions of the backcoating being in direct contact with the thermoplastic web at those sites on the web devoid of granular material. Thereafter, the backcoating is dried or cured, and a layer of adhesive such as pressure-sensitive or heat-activated adhesive is applied thereto. This procedure thus enables the assembly of patterned web material into laminates which include an activated adhesive layer while protecting the retroref].ective properties of the precise:Ly formed cube-corner pattern.
~ ore particularly, one aspect of the invention pertains to a flexlbleretroreflective cube corner type laminate sheet construction including a thermoplastic web w:Lth a l:Lght-receiving and transmitting first side and a second side coextensive with the first side, and a cube corner type retro-reflective pattern formed on at least a portion of the second side. The construction comprises a layer of hydrophoblc granular material deposited on the second side to cover selected portions of the formed cube corner retroreflective pattern with remaining portions of the second side devoid of said hydrophobic granular material. A layer of backcoating material is deposited on the second side to substantially completely overlay the hydro-phobic granular material without disturbing the pattern formed by the granular material. The backcoating material substantially fully contacts the portlons of the second side devoid of the granular material and is fixedly secured thereto, thereby ~ncapsulating the hydrophobic granular material between the second side and the backcoating layer. The particle si~e of the hydrophobic granular material is such that the area in which it is deposited will be effectively impervious to the backcoating material whereby the backcoating material is unable to penetrate the granular material and interact with the second side except in the area devoid of the granular material.
Another aspect of the invention comprehends a method for producing a cube corner type retroreflective laminate sheet construction comprising the steps of applying to a web of thermoplastic material having a retro-reflective cube corner formed pattern on at least a portion of one side a '7~
laya~ of hydl~ol-llol-l.c grfln~ll.nr ma~arl.nl. do~)091.t:ecl ~so a'J to Eorm a reg~.l.l..lr nnd ~al)en~l.nu nrrny Oll ~he rc~rorcE:I.ec~:Lve pattern and ~ormLng, as pnrt oE
thc nrray, n pl~lrnl:Lty o~ paths on the one .s:Lde clevold oE the hydrophobic grannlar mflter:Lal. A layer o~ backcoati.ng materi.al is applled to overlay the hydrophobic granular mater:Lal and to flll the paths, and i5 adhered to encapsulate the hydrophobic granular material between the formed side and the backcoating materlal. The particle 9ize of ths hydrophobic granular material is selected so that the area in whi.ch it i9 deposited will be effectlvely lmpervlous to the backcoating material whereby the backcoating material ls unable to penetrate the granular material and lnteract wlth the second slde except l.n the area devold of the granular materlal.
In a preferred embod.lment, an outer protectlve layer of thermoplastlc mater:Lal, used to provide additional weather resistant properties, is secured to the thermoplastic web on the side opposlte from that upon which the retro-reflective pattern is formed during or before the cube formlng process.
The completed lamlnate is then CutJ trimmed, or otherwise shaped for application to supporting surfaces, such as street or highway signs, and graphics or other indicia may thereafter be painted, printed, silk-screened, or otherwise affixed to the uppermost surface of the laminate, thus producing a readily and easily constructed highly retroreflective finished product.
These and further aspects of the present invention will become more apparent upon consideration of the accompanying drawings, wherein:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an enlarged perspective and somewhat schematic view of one preferred aspect of the retroreflective sheeting of the present invention as a completed construction;
FIG. 2 is a view along line 2-2 of Eig. 1;
-6a-B
Pla. 3 is n grcntly onl~lrged pl~ln vlew Illustr~ting a secllon ot the ~ormcd surfnce o~ reflectlve sheeting comprislng on~ aspect of ~he present inventlon;
~ la. 4 is a somewhnt schemntic Rnd symbolic vlew of the proaesses and rnnchinery utilized in n pre?erred Aspect ot the present inven~ion;
~ IG. 5 is fl plnn vlew o~ one form of screen p~ttern used to apply th~
hydrophobic gr~nul~r leyer of the present invention;
PIG. 6 is an enlnrged view, In partial detail, of an indivlduQI cell o~ ~he sheeling ot the present invention; and PIG. 7 is an enlarged perspectiv~ v~ew illustr~tln~ a ~econd preferred 10 embodiment of the retroreflective sheetin~ ot the present Invention.
D~rAll,ED_DESCRlPTlO~INGS
Reterring now to Pig. 3, the numeral 10 indicates generally B segment o~
cube-corner type retrorerlective thermopl~ic web used in forming the lamina~e or the present inventlon. As seen In Pig. 3, there is ~epicted the rear su~f~c~ ot a portion or (lexible retrorerleclive sheeting 12 ~ashioned rrom transp~rent thermopla5~jc ma~erial in web form which hQs formed thereon, preferRbly by embossing, a retrorenective ~nd repeating pRtterl of cube~orner re~lector element~
characterjzed by cu~e faces 14, 16 ~nd 18. In ~ preferred aspect of suc~ sh0~ting, sheet 1~ is formed from an impact-modified acrylic material having t~Y inhibitors or 20 absorbers ndded thereto, Qnd which, prior to embossing, had par~llel ~ront ~nd bnck surf~ces ~nd W1~5 initially on the order Or ~bout O.OOB inches thick. One such materi~l is known ns Plexiglas DR, sold by the ~ohm and HnAs Comp~ny.
The cube-corner pattern formed on sheeting 12 is formed in ~n optically precise, Iinely~etailed pattern. Por examplet as seen in Pig. ~, the depth to whlch the cube~orner pattern is embossed onto sheet 12 may be o~ the order or ~.OD338 inch, (dimension X~. As shown at dimension Y in Pig. 3, the cubes formed on sheet 12 may be spaced ap~rt by a distance on the order of about 0.0072 inch, ~r the depth as shown at X as set ~orth above~ While the cube pattern shown in ~lg. 1 i]lustrates cubes formed with their optical ~xes normal to the race Or sheet 12, it is 80 to be understood that other versions and p~tterns m~y also ~e utilized ~15 ~ormlng the retrore~ective web of the Inminnte of the presen~ invention.
~ e~errin~ now to Pig. 1, the numeral 20 indicstes gener~lly a roll ot retrorenectlve l~minate 22 manufactured In ~ccordance with prererred ~spec~s o~
the present InventlorI to be described hereinbelow. As hereln shown, Inmlnata 22 i~
rGlled onto Q core 24. A thermoplastic web 2~ h~ving a front or obvcrse ~urlrfl~o 28 , . .
'7~L~3 nnd ~ rcnr or roversc surtncc 30 upon which i~ embossed th0 cu~e-corner type retroretlective pnttern LLlustrated ln FLg. 3. Th~ thermop1astic web 26 may be on ~he ordcr or about 6 mils in thicknes~ (0.006 inch).
Bonded to the reverse surrsce 30 Or the thermoplasticw~b 26 i~
bsckcosting or ~ilm 32. In Q prererred sspect of the present inventlon, a hydrophobic granular silica materiRl 34 is Intetposed between th~ b~ckco~t tilm 32 and the reverse side 30 in ~ manner to be! Jescribed hereinbelow.
In sccorda.nce with a preterred embodiment of the pres~nt lnventlon, n layer ot adhesive 36 is bonded to a release sheet 38 in n prasently well-known 10 fnshic>n~ and is ~here~rter bonded to cured baokcost film 32 In order to proYld~ a tinished laminate 22 which includes a prcssure-6en~itive or heat-activated ~dhe~lve laycr 3~ upplied to sheeting 12 in a mBnn~r which preserves the retroretleetlv~
cluali~ics nnd properties ot the cube-corner pattern embossed thereon. The release sheet 38 is used to protect adhesive l~yer 36 until It is desired to npply l~minBte 2a to El given ~urf~ce.
Pig. 4 shows~ in schematic form, a preferred arrRngment ot equipment and sequence of operatlons to produce e retrorenectSve sheeting l~minnte ot the type shown ln ~ig. 3.
The applicat~on of adhesive directly to the reverse sid~ o~ Q CU~e-Corner 20 embossed thermopl~s~ic web 26 will cause ~n undesira~lo and unac~ceptable lo~s of retrorenectjye cap~bility. This ~rises from the contact ot the sdheQlve materi~l with the reverse side o~ embossed thermoplastic~ web 26, ~ ~ ~ the ~ ng o~ the "valleys rormed by the embossed pnttern Qnd the subseguent inter~ace formed between substances that ~re too similar in refractive indices to produce adequ~te retroreflection, so the transparent film can no longer utillze the phenomenon o~
total internQI renection to efticiently effect retroretlection or lJght. Tb solve thls problem, A sub~tantial portion of the cube~orner pattern either must be hermetjcQLly sealed with an air space ~etween the bsck wall ~nd the oube-corner elements, or the cube~orner elements must be backed in e way whirh would 30 preserve the rstrorenectlve properties o~ the ~ormed web while providing slte~ ror rirm ~lt~chment of an adhesive Isyer (or other adhesive m~terisl). Without such protection, and without such atteching sites, the use of, ~nd e~fectiveness o~ a retrore~lective embossed web is seriously compromlsed and curtslled.
Vnexpectedly, use of hydrophobio granular materials has been ~ound to artord such protection or optical properties. Among such materl~l~ aro xylen~ted~
glass particles, powdcred silicone rubber, end silane-tre~ted 8111c~.
.
.~24'~
As part Or the present inven~ion, It hns b en found thnt Q hydrophobicsilic~ mixture consisting principAlly of nmorphous silic~ treated w5th sllanes, when used to rill the v~lleys formed by the emboss¢d pnttern, preserve6 the retroreflective properties of the ~ormed pattern for mo t practical purposes~ Agaln, it is not known precisely why this etfect obtsins: it has been theorl~ed thet the point contact of gr~nules with the reverse ~ace of the ernbossed thermoplasti~ web ncts to preserve the retrore~lective properties ot the psttern, perhnps by preservlng A su~ticient ~ir interfnce with the reverse side ot the cube-corner pattern.
However, the present invention obtains excellent resu~ts even where the primary 10 silicn psrticlea used sre 6ignificQntly smaller thaIl~ for example, the pnrticle~
discussed in prior ~rt patents such flS ~ V~. Patent No. 3,924,929.
Use of such sllica ofrers advAntages such ns low prlce, avaIlAbJllty, ~nd ease nnd precision of forrnulation. It further provides unlque color a~d ref~ectlve chnrRcteristics to the tilm which improves the appenrance of the rilm even relative to the glass bead types heretofore commonl~ used.
As discussed hereinRbove with respect to the ~ et al reference, others h~ve nttempted to solve the problem-of loss of renectivlty by provIding Ups~andirlg walls or septn as pnrt of the rigid molded tront fscs pstîern, with the septa rorming indi~idual pockets for the npplication o~ granul~r ~ompound3 h~ving 20 pnrticle size~ far in excess of the silica particles used in the present inventlon.
The disadv~ntages to such nn approach, pnrticularly with respect to the cube~orner type embossed pattern utilized in the present invention are manirest. U~e o~ ri~id septa limit~ the size and shnpe o~ the cell. A separate mold must be formed for each type of retroreflective sheeting reguiring ~ ~ell size other th~n thQt formed in the origin~l mold. What is mennt by tne terrn "cell si~e" i~ the area bounded by or closed off by the walls to torm e single pocket ~or the grsnular backing material.
Formation o~ such septa in ~ relatively r;gid mold p~ttern m~nutactured to ~s fine ~nd precise a degree ot detMil as that shown in the present SnventSon al~o mny cause problems with respect to stripping the formed thermoplnstic web ~rom 30 the forming tool. This rnay particulsrly be a problem where the sept~ or wsll~
extend inwardly into the mold to n distAnce grenter than the depth oî the cube-corner pattern.
A preterred embodiment ot the present Invention includes the mixing of hydrophobic silic~ mixtur~e using hydrophobic sill~n, orgnn5c solvents, and thickener~, ~nd the app]lcat5On or this mixture~ whlle In n Ik1~id torm, to the re~/erYe YIde Or~
~he tormed therrnoplns~ic web 5n a desired pnttern One ndvantnge ot the pre~ont --9_ '7~
proccss nnd pr~uct is thQt thc p-lttern CAn ¢onvcnicntly be ch~nged to eftect chnng~s in rcrtcctive c~pabili~y oi~ ~hQ ~ilm, without changln~ the tov~5 u5ed In torming the embossed wcb. Thereatter, the partlQlIy coated or imprinted thermoplastic web is pnssed through a drylng oven which drives off the solvents used to torm thc mixture, thereby drying the p~ttern on the thermopl~s~5c ~heet. l'hepattern in which the silica is applied to th~ thermoplasiic web leave~ selccted por~ions or sites on the formed ~ace o~ the thermoplastic web devoid ot s~lica.
Re~errln~ now to Fig. 5, the numer~l 40 indicates ~enerally suoh fl selected p~ttern. Each runner or p~th 42 represents ~n ~rea on the reYerse surrace 10 ol therrnoplastic web 26 where no silica h~s been d~j~osited. E~ch ~quar~ or di~mond~h~ped nrea 44 represents ~n nren on the sur~Aoe Or thermopl~stic w~b 26 onto which tho slllos mixturc has been deposited.
As seen In Pig. 6, the nctual percentage of are~ covered by the ~ilic~
mixture is determined by the thicl<nes~ or width o~ each runner or path 4a, and the pa~tern selected lor deposition ol the silica, with the cell ~14 h~vln~ an are~
~ounded by the runners 42, and rully avail~ble ~or the reception and retrorenectlon o~ incident light by the embossed retroreflective pattern~ shown partl~lly ~t 4~.
Re~errlng now to Pig. 4"t may be seen that thermop1asti¢ web ~6 may be drawn directly ~rom ~n associS~ted rorming machine (not herein speciJ~ie~lly ~hown~
20 in a continuous process, or m~y be drawn ~rom a separ~te suwly reel onto which the embossed web 2~ has been wound (not herein specirical1y shown~ deslred, web 26 may be supported by a backing sheet (not hereln specilically shown3 coextensive with obverse face 28, leaving reverse sur-ace 30 exposed.
lt ~hould be noted ~hat re~erence to web 26 E1150 ~ncludes re~erence to a lsmin~te rormed by web 26 and a backing sheet such as described hereinabovc.
Web 26 is drRwn by, for example, powered rollers ~not herein 6peclfically shown), to ~ilicQ mixture ~pplication st~tion 48. ~ herein diagrAmmaticalty shown, a pre~erred me~ns and method Or applying the sill~a mJxture to web 26 may be accompllshed through use ot a screen-printing cylinder 50 which hQs moun~ed about 30 ~he outer periphery thereor, a metal screen lormed to provlde the shape or pattern to which it is desired to apply the ~llica mlxture~ Th~ mixtura Ts ~orced under pre~we from the interior of screen-printing drum 50 onto the reverse side 30 of the thermopla.stic web 26,~ As herein shown, the web 26 is directed by idler rol-ler 52 ~o pass bel:ween the screen-printing drum 50 and a backin~ roller 54, A prererred ~orm of the ~pp~ratus utllized to Apply th~ silica mlxturs et application station 48 consists of ~ drum prlnter manufacturod by Stork BrabAnt BY
-lU-.a~7~
o ~ lloxoc~r, llollnn(i, ot the lype hnvlnE n drum wlth clcclro-~ormed mcsh scrcer~s ovcr which n ~ oto-resist p~tSern ~such ~s used ~OI oonventionnt silk screen) mQy be moun~ecI, with n screcn pattern providing a dinmond cell ~Ize in the range of trom nbout 0.096 inch to 0.300 inch, nnd ~ runner or cell wall thIckness of trom flbout 0.010 inch to ~bout 0.050 inch. Vnriations Ih the shnpe or the cell~ ttern repeQt ot She cellc, nnd thickness of the runnerY msy be accolnplished by changing the printing screen used on screen-printing drum 50. Also, the con~t~nt wldth o~ theweb mny be of various sizes, and the printing 6creens used will be o~ ~ compntlble width.
ln its preferred rorm~ the silica mixture Is mede ~rom a. hydrophobi¢
silicn such ~s that manutactured by the Pigments Division ot De~uss~, ot Prnnk~urt, West Germnny, under the tr~de desi~nnti~n ~ipernat DIO~ A prererred composltlon ot ~he mixtur¢ includes hydrophobic silic~ in Q mixture contàining npproxlm~lely g8 perccn~ sllnne-trested silicon dioxide (SiO2~; 0.8 percen~ sodium oxide (N~20), ànd 0.8 percent o~ sulfur trioxide (SO~ non-polar nliphatic hydrocarbon soIvent c~rrjer; R polar solventj And, where desired or required, ~ thickening agent. One aliph~tic non-polnr hydrocarbon solYent successfully used is low odor mlner~l ~pirlts~
and Q workable mixture hss been creQted through use o~ an orgsnic nlcohol, pre~erQbly butsnol, as the polar solvent mQterisI. ~ smect;te clay-b~sed thixotropic 20 thickener also m~y be used in vQrying amounts to produce a well^derined screen-prinled p~ttern or the silic~ slurry on the embossed thermopl~stic web.
In ~ts preferred embodiment, the primary pQrticle size of the slllcs is ~bout 18 nanometers, and the Qgglomerated particle sizc of the hydrophoblc ~51ics in its final form is about S microns. However, it will be understood th~t the only critic~l limitation on the p~rticle size Is such that the ares in which It ;s deposited will be 6ubst~ntiE~IIy impervious to the backcoQting ma~eri~l 32, whereby the bsckcosting rn~teri~l ;s unable to penetrate the hydrophobic sillc~ and intersct with the cu~e-corner psttern except In those ~reas devoid ot the silic~
l~e p~rticular combinstion ot solvents and thickeners is import~nt to 30 sstistactory deposition and definition ot the silica in Q precise 6nd accurst~ pAttern.
Screen printing of p~rticulste material commonly requlr~s use ot resins or otherbinder5 to hold the deposited ~ar~icles in place. A resln or blnder c~nnot however be used in this instance because o~ the adverse eî~ect on renectlvlty ot the webbecsuse ot retrsctive Index Ylmil~rIties.
Another importnnt consider~tion 15 the rheology, or nOw chQrQct~rlstlcs o~
the silicn slurry ns It iB ~orced ~hrough thc printlng 6creen. The 61urry must ~,. ..
'74~'~
"rolnx," or thin ns lt is ~orce~l throllgh the screen npertures, ~nd therentter regain ulfricicnt viscoslty to rctaln a wel)-detined pattern with good leve!lng qll~lities and appenrance cha-acteristics. Yet another consider~tion 1~ use Or n ~olvent vehlcle which obtAins the a~orcmentioned qualities without ~ttacking or degrsding the thermoplastic web upon which the retroreflective pattern it ~ormed.
Use or pol~r solvents, such as butanol, enables the slurry to malntaln an increflsed concentrfltion of solids (silics~. Such solvents, however, resct with the thermoplastic matelial used to form the web. Non-polar solvent~, su¢h n5 mlnerB
spirits, preserve the embossed web, yet do not sct to provide n shtls~ctory slllca 10 p~ttern l`herefore Q blend of polnr snd non-polnr solvents has been round to be use~ul in carrying enough solids without degrading rerlectivity or degrading the web.
Preferably, the hydrophobic silicA is present in proportions rHnging rrom about t5 percent to about 35 percent by weight, the non-po2ar solvent carrler ls present in amounts ranging ~rom about 40 percent to about 70 percènt, the poIar solvent i5 present in amounts ranging from about 10 percent to about 30 percent, and the thickening ~gent may be present in arnounts from about 2 percent to About 8 percent. One preferred formulation of the silica mi~ture includes 20 percent ~y weight Sipernat D10 hydrophobic silica, 56 percent mineral SpilitS, 20 percent butanol, and 4 percent thickener. It has been found th~t such proportions preserve 20 the web while providing a useful silica p~ttern.
A~te~ application of the s51ica mixture, web 2~ is passed through ~
he~ting oven 56 where the resulting silic~ pattern is heated to drive off the orgnnic solvents without heQting web 26 to the ~oint where heat distortion o~ the cube-corner elements o~ the l~minate will occur.
Arter drying, the silicn is mechanically held to the cube~orner element~
on the reverse face 30 o~ web 26 by, it is believed, electroststic force~ and physical inter-engsgement Or the silica j~rticle~ themselves.
Thu~, RS web 26 exlts rnixture application stRtiOn 48~ It has t~ken on the rorm o~ n ~irst modified laminate 58, ~ ~, a web 26 h~ving cube~orner element3 30 with s precisly îormed pattern of silic~ mixture screened thereon over n pc~rtion Or the elements, wlth an uncovered portion Or the cube~orner elements stll~ exposed.
As modi~ied laminate 58 exits drying oven 5B, it t~kes on a second modi~led laminate construction 60 wherein the solvents present in the sillca mixture hnva been drlven o~ ~nd the silica itselr has remained dried into it~ ~raened-on p~ttern.
The second modi~ied laminnte 60 then enters n btlckcoatln~ apptl~ntion s~a~ion B2. The appllcatlon of n water-bnsed ~ckconting nccompllshw .qevor~l rcslllt~q. ~irst, tho~c nrons onto whlch no sillc~ has boen screcned or deposlted witlallow direc~ conlnct between the bnckco~ting nnd the revelse ~Ide 30 or the embosscd or otherwise ~ormed thermoplastic web a6, thus "wetting" web 2~ wlth the liquid backcoa~ing mix~ure. Second, a layer or b~ckcoating materi~l will oYerlay the silica pnttern formed on thermopl~stic web 26 ~nd, when applied etfecti-/ely, will not disturb or disrupt the printed or screened-on silic~ p~ttern. Third~ th~
backcoat;ng may then be dried and/or cured to provide a rirm ~tt~hment to thermopla5tjc web 26 to provide B flat, smooth ~nd integral surrace upon which further layers, such flg a l~yer or pressure-~ensitive or he~t-activ~ted adhesive m~y 10 be ef~ectively and conveniently applied, and to protectively cover or encapsulate the silica pattern. A surprising and unexpected result Is thQt the slllc~ prevent~
perrnefltlon by the liquid bnckcoating to the cube-corner i~ttern. As deYcribed nbove, such permention would adversely artect the reflectivlty of the rinal sssembled laminate.
Applicntion o~ the backcoating mix~ure to the second moditied laminata 60 msy be sccom~lished in a number o~ ways, such as by spraying, roller applicat;on, squeegeelng, or the like. The m~nner in which the bRckcoQt i~ appl;Qd will be determined by, inter ~ the precise formulation Or the backcoat and the pressure, or ~orc~, which can be withstood by the silica psttern aft~r i~ lu5 b~en 20 drie~.
Por purposes o~ illustration, a bsckcoating app~ication stat;on ~2 may be char~cterized fl~ having a supply header or tsnk 64 ~ommunicating with an flpplication means B6 which may ~e a nozzle or series of nozzles, or the 13ke. An implement such as a doctor bl~de 68 may be used to more unii~ormly spread the bnckcoating a~ter i~ has been applied without damaging the slllca pattern. A pl~ten 70 provides support ~or the second modified laminate 60 during application ot ths backcost .
A~ter application, the third modified Iflminate 72 enters drying oven 74i wherein the backcoat material is heat~ured, resulting in backcoating layer 32 as 30 shown in ~ig. 1.
Succes~tul use or fl backcorlting requires that the backcontlng ~ormulstion meet several p~srticu!Qrly important workln~ parRmeters. On~ ~s th~t the b~ckcoating have rlow charflcteristics such that ~he relatively narrow ancl 8hal10w runners formed by the silica pattern wlll be filled, while not dewetting or disturbing the dried ~llica p~tterri itselr. ~is me~r~ thflt the viscosity of the backco~ltln must be cnre~ully controlled to ~ssure thnt the bnckco~tlng chn be flppliod ~hilo 13~
'7~
cornplctely encnpsu~nt;ng wi~hout disturbing the sillc~ pnttern. Another chAr~c-~eristic Is that lhe b~ckco~ting cnnnot penetr~tQ or interRct with the npplied s(lica to reach the Inter~ace belween the sillc~ ~nd the cube-c~rner pnt~ern. Yet 8nother requirement is that the backcoatin~, when dried, hsve the reguired ~lexlbil5ty and toughness to withstand use in a laminate. Ideally, the b~ckcoflting ~hou~d also be or a color which enhances day~ime vislbility Or artlcles rnadé w3th ~uch l~minates.
Several preferred backcoatings have beerl utilized. ~ch may be characteri~ed generally as including a water-borne or w~ter-bssed polymerlc mixture or system, B whitening ~gent, Q defosmer, a thickener for use In ~d~ustlng the rin~l 10 viscosity~ and a pH-adJusting componont.
A ~irst prererred ~ormulation o~ n b~ckcoating i~ presented herewlth a~
Example 1-~ *
1. DP-101, a water-borne polymeric system consisting o~ about 34%
acrylic/urethane copolymer, 61% water and 5% coAlescent solvent, such a~ M-pyrol 6~.7% to 7~.7%
2. UCD-1D60Q, a pre~ispersed whitening agent (tltanium dioxide) containing about 72% solids 21.5% to ~3.5%
3. Balab 3017A, ~ de~oamer 0.4~6 to 0.~%
4. CP-15 (50 percent in water) acrylic/based thickener to ad)ust viscosity 1.596 to 2.5
5. Ammonla (28 percent aqueous sollJtion) to adJust pH
to 8.5 to 10.0 None to 0.~%
The foregoing mixture is ~ormed by sdding the detoamer to the ~ater-30 borne acrylic/weShane copolymer system with gentle ~tirrlng. Therea~ter, tha whitenin~ agent and the ammonia, i~ necessary, are added as gentle stirrlng l!s continued The ~hickener i8 thereatter added with incre~sin~ bl~dc speed and the entire mixture is ~stirred ror about 30 rninutes at m~derate speed. A preferred * 'l' r ~ nfl r k .~J
14~
.~
mix~r tor sllch nn operntion is mLInu~cturcd by Meyers En~lneering or E3ell, Cnli~ under the trade or model designntion "550."
DP-101 is n tr~de designation of Polyvinyl Chem5cal Industries, Inc, o~
WiJmlng~on, !~ssachusetts. While the preclse ~ormulation i3 not known, Polyv~nyl Chemic~l Industries has flssigned the trade deslgnst5On DP-101 ,~, to the p~rticular urethane/acrylic copolymer resin utilized ~n lhe ~or~going backcoat ~ornnu]atlon.
DP-lOL is de~ined by Polyvi~yl Ch~mic~ll Inc. as ~ water dispersio~ of ~
gr~ft copolymrr of an aliphatic urethane ~oined to a ~tyrene-acryllc copolymer.
Its wei~ht per gallon is 8.6 pounds, its acid value is ~.5, and its index of reEractlon is 1.3956. Its molerular weight, ~ith respect to tha~ portlon of the re~in solub:Le in tetrahydroE~Iran, when measured by GPC, is: Mw 450,569;
M 65,660; and M~ 1,204,300, and its viscoslty, as measured by ~he Brookfield Viscosity Method a~ 25C is 200 cps. UCD-1060 is a trade designation of the Universal Color Dispersion Company of Lansing, Illinois, used to identify a dispersion product for water-based systems. Balab 3017-A is also identified by the trade designation bubble breaker and is a product of the Organic Division of Witco Chemical Corporation of New York, N.Y.
CP-15 i~ a trade designation of the Rohm ~nd Haas Compan~r and is an acrylic-based thickening agent. M~yrol ls Q trade designation of the G.A,P. Corporation 20 Used to identify a methy~pyrolictive coalescent solvent. The amount o~ organlc , co~lescent in ~he water based systems pre7erably should not exceed, sbout 10% by formula weight, otherwise the backcoating rnight permeate the hydrophob5c granular matter into the ~ormed cube-corner p~ttern.
A second ~ormulntlon for lhQ backcoetlng mlxturo l~ herewlth pr~sent~i ag example 2 and ndd~ a cross-linking agent to irnprov~ dur~blllt~s Exnmple 2 1. DP-101, a wa~er-borne polymerlc system consisting or ~bo~it 3~%
~crylic/ur~thane copolymer, B1% water, and 5% co~lescent solvent such ag M-pyrol qO~ to ~0%
2. VCD-1060~, a pre dispersed whitenlng ngent (tit~nlurn dioxide) cont~inlng nbout 72% solids 10% to ~0%
3. BYK-W, a deJoamer 1~%
4. De-ionizeJ water . 5%
5. Ammoni~ ~28 percent ~queous ~olution) to adJust pH
to 3.5 to 9.û Non~ to 0.~
A~ter the foregolng ingredients ~vo been mixed, and Immedi~tely prlor to applic~tlon, a qusntity Or the ~oregoing m5xture Is placed in a mlxing vess~l, Hnd * Trademarks .:0 -15a-lX~
n frcshly prep~lred solullon ot cross-)inking ngent i.s rnlxed therewlth. A prererrod cross-linklng AgCnt genernlly is a polyfunctionnl Qziridlnel such ~ CX-100, m~nufnctured by Poyvlnyl Chemic~l Industrtes"nc, or Wilmington~ M~ chusetts.
preterrod prepnrntion consists o~ 35 Ibs. ot backconting rnixture comblned wlth 150 gr~lm~ or CX-100, dissolved in 150 grams or water, BYK-W is a de~oamer manutnctur~d by MalJinckrodt ot P5elville, ~ew York.
In thi~ embodiment, the addition o~ the cros~ linking agent enhnnces th~
weathernbility of the ~inished laminnte by increnslng the dur~bllity llnci tou~hness o~
l 0 the t~ckco~t~n~, A third formulntion ~or the backconting mAterJal 58 herewlth presented n~
exllmple 3:
1. Emulsion ~-182~, a wQter-borne polymeric Iscrylic emulsion 42.1% to ~2.1%
. Water 2.2% to 12.a~6 . Ethylene glycol, ~n anti-skinnlng nOw improvement agent 1.5% to 2,59 4. UCD 10~0Q, a pre dispersed whitening agent (titsnium dioxide) a~02% to ~B.a%
5. Syloid 16g, silicone dioxide fl~tting a~ent to prevent blocking , ~.a% to 5.a%
to 8.5 to 10.0 None to 0.~%
The foregoing mixture is ~ormed by sdding the detoamer to the ~ater-30 borne acrylic/weShane copolymer system with gentle ~tirrlng. Therea~ter, tha whitenin~ agent and the ammonia, i~ necessary, are added as gentle stirrlng l!s continued The ~hickener i8 thereatter added with incre~sin~ bl~dc speed and the entire mixture is ~stirred ror about 30 rninutes at m~derate speed. A preferred * 'l' r ~ nfl r k .~J
14~
.~
mix~r tor sllch nn operntion is mLInu~cturcd by Meyers En~lneering or E3ell, Cnli~ under the trade or model designntion "550."
DP-101 is n tr~de designation of Polyvinyl Chem5cal Industries, Inc, o~
WiJmlng~on, !~ssachusetts. While the preclse ~ormulation i3 not known, Polyv~nyl Chemic~l Industries has flssigned the trade deslgnst5On DP-101 ,~, to the p~rticular urethane/acrylic copolymer resin utilized ~n lhe ~or~going backcoat ~ornnu]atlon.
DP-lOL is de~ined by Polyvi~yl Ch~mic~ll Inc. as ~ water dispersio~ of ~
gr~ft copolymrr of an aliphatic urethane ~oined to a ~tyrene-acryllc copolymer.
Its wei~ht per gallon is 8.6 pounds, its acid value is ~.5, and its index of reEractlon is 1.3956. Its molerular weight, ~ith respect to tha~ portlon of the re~in solub:Le in tetrahydroE~Iran, when measured by GPC, is: Mw 450,569;
M 65,660; and M~ 1,204,300, and its viscoslty, as measured by ~he Brookfield Viscosity Method a~ 25C is 200 cps. UCD-1060 is a trade designation of the Universal Color Dispersion Company of Lansing, Illinois, used to identify a dispersion product for water-based systems. Balab 3017-A is also identified by the trade designation bubble breaker and is a product of the Organic Division of Witco Chemical Corporation of New York, N.Y.
CP-15 i~ a trade designation of the Rohm ~nd Haas Compan~r and is an acrylic-based thickening agent. M~yrol ls Q trade designation of the G.A,P. Corporation 20 Used to identify a methy~pyrolictive coalescent solvent. The amount o~ organlc , co~lescent in ~he water based systems pre7erably should not exceed, sbout 10% by formula weight, otherwise the backcoating rnight permeate the hydrophob5c granular matter into the ~ormed cube-corner p~ttern.
A second ~ormulntlon for lhQ backcoetlng mlxturo l~ herewlth pr~sent~i ag example 2 and ndd~ a cross-linking agent to irnprov~ dur~blllt~s Exnmple 2 1. DP-101, a wa~er-borne polymerlc system consisting or ~bo~it 3~%
~crylic/ur~thane copolymer, B1% water, and 5% co~lescent solvent such ag M-pyrol qO~ to ~0%
2. VCD-1060~, a pre dispersed whitenlng ngent (tit~nlurn dioxide) cont~inlng nbout 72% solids 10% to ~0%
3. BYK-W, a deJoamer 1~%
4. De-ionizeJ water . 5%
5. Ammoni~ ~28 percent ~queous ~olution) to adJust pH
to 3.5 to 9.û Non~ to 0.~
A~ter the foregolng ingredients ~vo been mixed, and Immedi~tely prlor to applic~tlon, a qusntity Or the ~oregoing m5xture Is placed in a mlxing vess~l, Hnd * Trademarks .:0 -15a-lX~
n frcshly prep~lred solullon ot cross-)inking ngent i.s rnlxed therewlth. A prererrod cross-linklng AgCnt genernlly is a polyfunctionnl Qziridlnel such ~ CX-100, m~nufnctured by Poyvlnyl Chemic~l Industrtes"nc, or Wilmington~ M~ chusetts.
preterrod prepnrntion consists o~ 35 Ibs. ot backconting rnixture comblned wlth 150 gr~lm~ or CX-100, dissolved in 150 grams or water, BYK-W is a de~oamer manutnctur~d by MalJinckrodt ot P5elville, ~ew York.
In thi~ embodiment, the addition o~ the cros~ linking agent enhnnces th~
weathernbility of the ~inished laminnte by increnslng the dur~bllity llnci tou~hness o~
l 0 the t~ckco~t~n~, A third formulntion ~or the backconting mAterJal 58 herewlth presented n~
exllmple 3:
1. Emulsion ~-182~, a wQter-borne polymeric Iscrylic emulsion 42.1% to ~2.1%
. Water 2.2% to 12.a~6 . Ethylene glycol, ~n anti-skinnlng nOw improvement agent 1.5% to 2,59 4. UCD 10~0Q, a pre dispersed whitening agent (titsnium dioxide) a~02% to ~B.a%
5. Syloid 16g, silicone dioxide fl~tting a~ent to prevent blocking , ~.a% to 5.a%
6. Dimethylamino eth~nol p~-sdfusting ~olvent 0~6 to 0,5%
7, E~lab 3017A defoamer 0.696 to 1~0%
8, Tex~nol solvent, a co~tescent ~olvent ~or improved ~ilm tormlstion 1.~% to t.
g. CP-15 (50 percent in water) acrylic~sed thickener to sd~ust viscoslty None ~o 1.~9 The toregoing bnckco~ting is prep~red.by.addlng.tho cle~o~mer to the wnter~borne 6ystem wilh genlle mixing, then ndding the w~ter, tho nntl-~klnnlnR
* 'l' r ~ r k , ~
,.. ~. , .
'7~
ngcnt, tho prc-disperscd whitcniIlK ngen~ nnd thc amine while contInuIng ~entlc mixinK. Thoreart~r~ the conlescent solv~nt Is ndded. Bl~de speed 5~ thcn Increa~ed nnd the ~hickener is Added to adjust the viscoslty to th~ deslred level ~nd the resul~ing mix~ure is then stirred nt moderate speed rOr 30 mlnute~
Emulslon ~-18~9 is A trade desienation o~ th~ Rohm and Tla~ Compcny of PhtladeLphla, Pennsylvania~ for an acrylic e~lul6ion vehlcle. Em~lsion E-1829 ~ o sold un~er the trade designatlon 'Rhoplex AC-829r and i~ a 100% acryllc em~ lon polymer made by typLc~l emulslon polymerl~tlon processes. with ~I mol~cular welght ln exce~ of l,OOO,OC)0. Its welght per g~llon ls 8.35 L0 pound~, Lt~ vL~coslty is 1,200 to Z,300 cP and i~9 pH range :Ls 8.6 to 9.1.
Lt~ 81~L~ trnn~sltioll temperature :Ls 3C. Syloid is a trade de~igna~ion of the ~)avlcl~on Chemical Company, a divlsion of W. R. Grace, of Baltimore, M~ryland for a sllicon dioxlde fl~ttlng agent. Texanol is a trade designation of the Eastment Chem:lcal Products Company of Kingsport, Tennessee, used to ldentlfy a coalesclng agent.
Referring now to Fig. 2, ~ partial æctIonal v~w o~ c schemat5c portion o~ embossed thermoplestic Yreb 26 arter ~pplication o~ both ~illc~ 34 and backco~ting 32 is shown. A~ therein seen, reverse sld~ 30 of thermopl~stlc web includes ~ ~erie~ of v~lleys, indicated generally at 7B. Th~ valleys 7ff schematically 20 represent the cube-corner elemen~s found in web 26 when the cube-corner pattern shown in Pig. I is embossed onto thermopiast3c web 2B. When the 5lljCQ layer 34 I~
applied, the valleys between adjacent cube-corner elements 76 are tilled (except where the screen pattern leaves web 26 exposed) and, ~n a preterred embodiment or the invention, enough 6jIjCA 34 is applied to extend a distance o~ about 0.0001 to about 0.003 inch above the embossed surtace of thermoplastic web ~S, as ~hAracter-ized by dimension A of Pig. 2. In l;ke fashion, the backcoQt layer 3~ i~ 2pplied to a th;ckness B o~ about 0.002 to ~bout 0.004 inch above the silic~ l~yer ~4. Where runners or paths 42 are formed, esch such runn r consist3 o~ the bacKcoQt materl~
which extends downward to wet the ~loor ot each valley 76 to ~ tot~l depth C, a3 30 shown in Pig. ~ which, prererrably, is about O.Op6 inch. In e pre~erred èmbodIment of the present invention, each such runner is 0.001 inch deep and, as ch~r~oterized by dimensjon D in l~ . 2 ~nd 6, m~y be on ~he order ot 0.û15 inch wlde.
In the embodlment hereln Ulu~tr~ted, each discrQte element or th~ applled silicn p~t~ern Is square in shape wlth the length of e~ch side of the ~qu~re ch~rQcterized by dimension :E~ In Pigs. 2 and 6. As herelnabove descrlbed, the p~rcent~ge of surfsce sre~ svaila~le tor retrore~lection m~y be ~dJusted by ~d¦usting the dimension~ D snd ~ as shown in ~ " 2 ~nd 6. Wher~, ~or exQmple, dimenslon D Is 0.015 Inch und dimension E ~s 0.200 inch, the ef~ectlve ~urtace available for retroretIec~ion 1~ 84 percent. Where dimenslon D 1~ 0.027 Inch ~nd dimenslon ~ l~
0.138 Inch, appro3timately 70 percent ot the surfnce of the resultlng ~h~t pre~erv~ -retroretlec~ive chdracteristics. With a dimenslon D of 0.029 Inch and 0 dImenslon ~R
-17.1- . . . /lB
~, ~'~
y~
t 0 096 inch, npproximntely 55 pcrcent or ~hc totnl surtncc ot the resultin~ sheet retnins retroreflectivc propcrties.
Thus, the degree to whlch the resulting lamin~r sheet returns Incldent light towards it~ source may be adJusted independent o~ the actual cube~orner ~ype pattern rormed on thermoplastic web 26, in n manner which is mùch more convenient rlnd e~ficacious thnn chtln~ing the mold din)ensions or character~stics used to produce the embossed cube-corner pattern.
Reterring again to Yigs. 1 tlnd 4, after fourth modiried IQminat0 ~4 exlts drying oven 74, A pressure-sensitive or heat-nctivated adhesive l~yer 3~ m~y then ~e 10 applied by tnking the resultin~ laminate 84 and drnwing ~t past a st~tion whel~e ~
btlcking or release ~heet 38, pre-coated with adhesive 36, m~y be layered d~rectly onto b~okcoating 3~, resulting in A completed laminate a2 as shown In Pig. 1.
~in~lly, if one is used, the carrier Stleet is stripped away, exposing obver~e ~c~ 28 as the light-receiving surface o~ the finished laminate a2.
It should ~e noted th~t the foregoing exRmples and pre~erred embodiments have been presented with respect to a cube-corner embossed pattern hav~n~ h depth characteriæd by dimension X in Fi~. 2 o~ 0.004 inch. It is contempltlt~d thAt pQtterns of Yarying depth and vsrying dimensions may be utllized, and that th~
dimensions herein discussed for the depth o( silica applied, and thP wldth end depth 20 o~ the runners therby formed, mtly be varled without departing rrom the splrit and ~cope o~ the inv¢ntion as herein d;scussed.
The rinished sheet will have the physical characteristlcs enabl~ng St to substantially meet specification ~P-79 for reflective sheeting, and it~ rene¢tive propertses can easily be varied by utilizing t~ different screen pattern. Moreover, the whiteness achieved by the existing laminate backcoating ~ubstantltllly enhance~
the daylight estheti¢s o~ the finished material. The he~ting oit the lnminat~ durlng the drying and curing of the silica, backcoating or adhesive, also may have an e~rect on the rlnal reflective performance of the lamlnate, dependent upon th~
characteristics of the initial tool and the material chosen for ths film. It has been 30 determined that for optimum per~ormanee, the laminate should not be heated above 180P during these vIlrious processing ~teps for the preterred embodiment disclosed hereln.
It mey also ~e noted that while the silica pattern hereln presented 19 series or 6qutlres turned to present a dit~mond-like pnt~ern, other cell ~IZe5 and sh~pe~ are tllso possible, wherever they appear ettlc~cious ~or purpo~e~ of ~r~orrnr~nce or ~ppetlrnnce, ~nd are within the splrlt ~nd 8cope of ~ha Inventlon RS
here5n discu~ed l3nd citl;med. -1~
~ s previously noted, Pig. 7 illuslrntes nnother preferred embodlment of thc prcsent invenlion. In this embodiment, Q l~yer 25 o~ fl more weather reslstant thermopl~stlc material ~hnn thQt forming web ~, such ~ unmodi~led or VV
modified, polymelhyl methacrylate, Is lemin~ted to the Impect modlfied ~crylic rorming web 2~. In its preferred torrn, layer 25 wlll be ~bout ,0003 in~h, ~nc1 wlll no~ exceed .0005 Inch ~0.5 mil) in thicknessl. lt has been round th~t the provis ion oi ~his added L~yer provldes ndditional weatherlng ch~rs.cterlstics needed for certeln environmcnts, while, when not exceeding the noted thickness, permits th~ total laminate to rema;n surriciently flexible. Pre~erred materlQI~ in thl~ embodirnent may be thll~ sold under the trflde designQtion V0S2 or V044 by the Rohm ~ Hnas CompQny, or a polyarylate sold under the trQdc design~t50n Ardel~ by ~Jnlon Carblde.
Yllrlous tcchniques m~y be employed to apply thls outer l~yer to the web beror¢ the silicQ and b~ckco~tlng ls npplied. For example~ the additionQI layer ot thermoplastic mnterial mey be epplied by solvent casting or m~y be co-exttuded wlth the inltlal til m .
A preferred formulHtion for the outer Isyer 25 include~ use ot Korad-~
the trade name or a modi~ied polymethyl methacrylat~ rn~nutactur~d by Polymeric Extruded Productg, Inc. o~ New~rk, ?~ew Jersey. Such materi~l lncluds3 U.V. iight absorbing substances, and is cross-linked to a nexible, rubber base substance, adding 20 flexibility. In pQrticulnr, use ot Tinuvin234, a benzotriazol compound m~nuractured by Geigy, is used as a UV inhibitor. This substance is lcnosvn chemic~lly a~
2~2H-benzotria~ol-2-yl~4-methyl-phenol. Kor~d-D thermoplasti~ is descrlbed in United ~tates Patent No. 3,562,235, issued on ~ebruary ~, 1971. When Korad-13 thermopla~tic i5 used, it may be applied hS a 2 mil outer l~yer durlng the cube ~orming process, or it m~y be co-extruded with,the web 26 before such formatlon,in a layer 1 mil thick, or it may be applied In solution directly to the web 28 in a layer 1/2 rnil thick. lhe particular thickness wIll depend in part on the tot~l thickness parame~ers of the ~inished laminate.
While the ~oregoing has presented varlous specific prererred em~odiments, 30 it is to be understo~d that these embodiments have been present~d by wQy o~
example only. It is expected that others will perceive dir~erences which, while varying ~rom the foregoing, do not depart rrom the spririt and scope o~ the invention as hereln cl~imed and described.
* Trademarks , . . .
g. CP-15 (50 percent in water) acrylic~sed thickener to sd~ust viscoslty None ~o 1.~9 The toregoing bnckco~ting is prep~red.by.addlng.tho cle~o~mer to the wnter~borne 6ystem wilh genlle mixing, then ndding the w~ter, tho nntl-~klnnlnR
* 'l' r ~ r k , ~
,.. ~. , .
'7~
ngcnt, tho prc-disperscd whitcniIlK ngen~ nnd thc amine while contInuIng ~entlc mixinK. Thoreart~r~ the conlescent solv~nt Is ndded. Bl~de speed 5~ thcn Increa~ed nnd the ~hickener is Added to adjust the viscoslty to th~ deslred level ~nd the resul~ing mix~ure is then stirred nt moderate speed rOr 30 mlnute~
Emulslon ~-18~9 is A trade desienation o~ th~ Rohm and Tla~ Compcny of PhtladeLphla, Pennsylvania~ for an acrylic e~lul6ion vehlcle. Em~lsion E-1829 ~ o sold un~er the trade designatlon 'Rhoplex AC-829r and i~ a 100% acryllc em~ lon polymer made by typLc~l emulslon polymerl~tlon processes. with ~I mol~cular welght ln exce~ of l,OOO,OC)0. Its welght per g~llon ls 8.35 L0 pound~, Lt~ vL~coslty is 1,200 to Z,300 cP and i~9 pH range :Ls 8.6 to 9.1.
Lt~ 81~L~ trnn~sltioll temperature :Ls 3C. Syloid is a trade de~igna~ion of the ~)avlcl~on Chemical Company, a divlsion of W. R. Grace, of Baltimore, M~ryland for a sllicon dioxlde fl~ttlng agent. Texanol is a trade designation of the Eastment Chem:lcal Products Company of Kingsport, Tennessee, used to ldentlfy a coalesclng agent.
Referring now to Fig. 2, ~ partial æctIonal v~w o~ c schemat5c portion o~ embossed thermoplestic Yreb 26 arter ~pplication o~ both ~illc~ 34 and backco~ting 32 is shown. A~ therein seen, reverse sld~ 30 of thermopl~stlc web includes ~ ~erie~ of v~lleys, indicated generally at 7B. Th~ valleys 7ff schematically 20 represent the cube-corner elemen~s found in web 26 when the cube-corner pattern shown in Pig. I is embossed onto thermopiast3c web 2B. When the 5lljCQ layer 34 I~
applied, the valleys between adjacent cube-corner elements 76 are tilled (except where the screen pattern leaves web 26 exposed) and, ~n a preterred embodiment or the invention, enough 6jIjCA 34 is applied to extend a distance o~ about 0.0001 to about 0.003 inch above the embossed surtace of thermoplastic web ~S, as ~hAracter-ized by dimension A of Pig. 2. In l;ke fashion, the backcoQt layer 3~ i~ 2pplied to a th;ckness B o~ about 0.002 to ~bout 0.004 inch above the silic~ l~yer ~4. Where runners or paths 42 are formed, esch such runn r consist3 o~ the bacKcoQt materl~
which extends downward to wet the ~loor ot each valley 76 to ~ tot~l depth C, a3 30 shown in Pig. ~ which, prererrably, is about O.Op6 inch. In e pre~erred èmbodIment of the present invention, each such runner is 0.001 inch deep and, as ch~r~oterized by dimensjon D in l~ . 2 ~nd 6, m~y be on ~he order ot 0.û15 inch wlde.
In the embodlment hereln Ulu~tr~ted, each discrQte element or th~ applled silicn p~t~ern Is square in shape wlth the length of e~ch side of the ~qu~re ch~rQcterized by dimension :E~ In Pigs. 2 and 6. As herelnabove descrlbed, the p~rcent~ge of surfsce sre~ svaila~le tor retrore~lection m~y be ~dJusted by ~d¦usting the dimension~ D snd ~ as shown in ~ " 2 ~nd 6. Wher~, ~or exQmple, dimenslon D Is 0.015 Inch und dimension E ~s 0.200 inch, the ef~ectlve ~urtace available for retroretIec~ion 1~ 84 percent. Where dimenslon D 1~ 0.027 Inch ~nd dimenslon ~ l~
0.138 Inch, appro3timately 70 percent ot the surfnce of the resultlng ~h~t pre~erv~ -retroretlec~ive chdracteristics. With a dimenslon D of 0.029 Inch and 0 dImenslon ~R
-17.1- . . . /lB
~, ~'~
y~
t 0 096 inch, npproximntely 55 pcrcent or ~hc totnl surtncc ot the resultin~ sheet retnins retroreflectivc propcrties.
Thus, the degree to whlch the resulting lamin~r sheet returns Incldent light towards it~ source may be adJusted independent o~ the actual cube~orner ~ype pattern rormed on thermoplastic web 26, in n manner which is mùch more convenient rlnd e~ficacious thnn chtln~ing the mold din)ensions or character~stics used to produce the embossed cube-corner pattern.
Reterring again to Yigs. 1 tlnd 4, after fourth modiried IQminat0 ~4 exlts drying oven 74, A pressure-sensitive or heat-nctivated adhesive l~yer 3~ m~y then ~e 10 applied by tnking the resultin~ laminate 84 and drnwing ~t past a st~tion whel~e ~
btlcking or release ~heet 38, pre-coated with adhesive 36, m~y be layered d~rectly onto b~okcoating 3~, resulting in A completed laminate a2 as shown In Pig. 1.
~in~lly, if one is used, the carrier Stleet is stripped away, exposing obver~e ~c~ 28 as the light-receiving surface o~ the finished laminate a2.
It should ~e noted th~t the foregoing exRmples and pre~erred embodiments have been presented with respect to a cube-corner embossed pattern hav~n~ h depth characteriæd by dimension X in Fi~. 2 o~ 0.004 inch. It is contempltlt~d thAt pQtterns of Yarying depth and vsrying dimensions may be utllized, and that th~
dimensions herein discussed for the depth o( silica applied, and thP wldth end depth 20 o~ the runners therby formed, mtly be varled without departing rrom the splrit and ~cope o~ the inv¢ntion as herein d;scussed.
The rinished sheet will have the physical characteristlcs enabl~ng St to substantially meet specification ~P-79 for reflective sheeting, and it~ rene¢tive propertses can easily be varied by utilizing t~ different screen pattern. Moreover, the whiteness achieved by the existing laminate backcoating ~ubstantltllly enhance~
the daylight estheti¢s o~ the finished material. The he~ting oit the lnminat~ durlng the drying and curing of the silica, backcoating or adhesive, also may have an e~rect on the rlnal reflective performance of the lamlnate, dependent upon th~
characteristics of the initial tool and the material chosen for ths film. It has been 30 determined that for optimum per~ormanee, the laminate should not be heated above 180P during these vIlrious processing ~teps for the preterred embodiment disclosed hereln.
It mey also ~e noted that while the silica pattern hereln presented 19 series or 6qutlres turned to present a dit~mond-like pnt~ern, other cell ~IZe5 and sh~pe~ are tllso possible, wherever they appear ettlc~cious ~or purpo~e~ of ~r~orrnr~nce or ~ppetlrnnce, ~nd are within the splrlt ~nd 8cope of ~ha Inventlon RS
here5n discu~ed l3nd citl;med. -1~
~ s previously noted, Pig. 7 illuslrntes nnother preferred embodlment of thc prcsent invenlion. In this embodiment, Q l~yer 25 o~ fl more weather reslstant thermopl~stlc material ~hnn thQt forming web ~, such ~ unmodi~led or VV
modified, polymelhyl methacrylate, Is lemin~ted to the Impect modlfied ~crylic rorming web 2~. In its preferred torrn, layer 25 wlll be ~bout ,0003 in~h, ~nc1 wlll no~ exceed .0005 Inch ~0.5 mil) in thicknessl. lt has been round th~t the provis ion oi ~his added L~yer provldes ndditional weatherlng ch~rs.cterlstics needed for certeln environmcnts, while, when not exceeding the noted thickness, permits th~ total laminate to rema;n surriciently flexible. Pre~erred materlQI~ in thl~ embodirnent may be thll~ sold under the trflde designQtion V0S2 or V044 by the Rohm ~ Hnas CompQny, or a polyarylate sold under the trQdc design~t50n Ardel~ by ~Jnlon Carblde.
Yllrlous tcchniques m~y be employed to apply thls outer l~yer to the web beror¢ the silicQ and b~ckco~tlng ls npplied. For example~ the additionQI layer ot thermoplastic mnterial mey be epplied by solvent casting or m~y be co-exttuded wlth the inltlal til m .
A preferred formulHtion for the outer Isyer 25 include~ use ot Korad-~
the trade name or a modi~ied polymethyl methacrylat~ rn~nutactur~d by Polymeric Extruded Productg, Inc. o~ New~rk, ?~ew Jersey. Such materi~l lncluds3 U.V. iight absorbing substances, and is cross-linked to a nexible, rubber base substance, adding 20 flexibility. In pQrticulnr, use ot Tinuvin234, a benzotriazol compound m~nuractured by Geigy, is used as a UV inhibitor. This substance is lcnosvn chemic~lly a~
2~2H-benzotria~ol-2-yl~4-methyl-phenol. Kor~d-D thermoplasti~ is descrlbed in United ~tates Patent No. 3,562,235, issued on ~ebruary ~, 1971. When Korad-13 thermopla~tic i5 used, it may be applied hS a 2 mil outer l~yer durlng the cube ~orming process, or it m~y be co-extruded with,the web 26 before such formatlon,in a layer 1 mil thick, or it may be applied In solution directly to the web 28 in a layer 1/2 rnil thick. lhe particular thickness wIll depend in part on the tot~l thickness parame~ers of the ~inished laminate.
While the ~oregoing has presented varlous specific prererred em~odiments, 30 it is to be understo~d that these embodiments have been present~d by wQy o~
example only. It is expected that others will perceive dir~erences which, while varying ~rom the foregoing, do not depart rrom the spririt and scope o~ the invention as hereln cl~imed and described.
* Trademarks , . . .
Claims (83)
1. A flexible retroreflective cube corner type laminate sheet construction including a thermoplastic web with a light-receiving and transmitting first side and a second side coextensive with said first side, and a cube corner type retroreflective pattern formed on at least a portion of said second side, said construction comprising:
a layer of hydrophobic granular material desposited on said second side to cover selected portions of said formed cube corner retroreflective pattern with remaining portions of said second side devoid of said hydro-phobic granular material; and a layer of backcoating material deposited on said second side to substantially completely overlay said hydrophobic granular material without disturbing the pattern formed by said granular material, said backcoating material substantially fully contacting said portions of said second side devoid of said granular material and being fixedly secured thereto, thereby encapsulating said hydrophobic granular material between said second side and said backcoating layer, the particle size of said hydrophobic granular material being such that the area in which it is deposited will be effectively impervious to said backcoating material whereby said backcoating material is unable to penetrate said granular material and interact with said second side except in the area devoid of said granular material.
a layer of hydrophobic granular material desposited on said second side to cover selected portions of said formed cube corner retroreflective pattern with remaining portions of said second side devoid of said hydro-phobic granular material; and a layer of backcoating material deposited on said second side to substantially completely overlay said hydrophobic granular material without disturbing the pattern formed by said granular material, said backcoating material substantially fully contacting said portions of said second side devoid of said granular material and being fixedly secured thereto, thereby encapsulating said hydrophobic granular material between said second side and said backcoating layer, the particle size of said hydrophobic granular material being such that the area in which it is deposited will be effectively impervious to said backcoating material whereby said backcoating material is unable to penetrate said granular material and interact with said second side except in the area devoid of said granular material.
2. The construction of Claim 1, wherein said hydrophobic granular material is deposited so as to form a regular and repeating array.
3. The construction of Claim 1, wherein said hydrophobic granular material is deposited so as to form a discrete, regularly-spaced array of pattern elements, each said element being surrounded by contiguous portions of said second side devoid of said granular material.
4. The construction set forth in Claim 3, in which said array of cube-corner pattern elements repeats itself in regular intervals.
5. The construction of Claim 1 wherein said hydrophobic granular material is hydrophobic silica.
6. The construction of Claim 1, wherein said hydrophobic granular material has a primary particle size of about 18 nanometers.
7. The construction of Claim 1, wherein said layer of granular material consists initially of a slurry comprising a hydrophobic granular material, a polar solvent, and a non-polar solvent, said polar solvent and said non-polar solvent present in relative proportions sufficient to allow deposition of said hydrophobic granular material in a well-defined pattern on said thermoplastic web.
8. The construction of Claim 7 wherein said granular material is hydrophobic silica.
9. The construction of Claim 7 wherein said polar solvent is an aliphatic alcohol.
10. The construction of Claim 7 wherein said polar solvent is butanol.
11. The construction of Claim 7 wherein said non-polar solvent is mineral spirits.
12. The construction of Claim 7 wherein said polar solvent is present in an amount from about 10% to about 30% of said slurry, and said non-polar solvent present in an amount from about 40% to about 70% of said slurry.
13. The construction of Claim 7 wherein said polar solvent is present In an amount of about 15% of said slurry.
14. The construction of Claim 7, wherein said slurry consists of from about 15% to about 35% of said hydrophobic granular material, from about 10% to about 30% of said polar solvent, and from about 40% to about 70% of said non-polar solvent.
15. The construction of Claim 7, wherein said slurry includes a thixotropic thickner.
16. The construction of Claim 1, wherein said backcoating consists essentially of a polymeric or copolymeric water-based system.
17. The construction of Claim 16, wherein said backcoating includes a major proportion of an acrylic/urethane copolymer.
18. The construction of Claim 16, wherein said backcoating includes a major proportion of a polymeric acrylic water-borne system.
19. The construction of Claim 16, wherein said backcoating comprises an acrylic/urethane copolymer, a whitening agent, and any acrylic-based thickening agent.
20. The construction of Claim 19, wherein said backcoating includes a defoaming agent.
21. The construction of Claim 16 wherein said backcoating comprises a polymeric acrylic system, a whitening agent, and a thickening agent.
22. The construction of Claim 16 wherein said backcoating comprises an acrylic/urethane copolymer, a whitening agent, a thickener and a cross-linking agent.
23. The construction of Claim 22 wherein said backcoating includes a defoaming agent.
24. The construction of Claim 23 wherein said backcoating, when dried, comprises of about the following constituents by weight: 73.1%
acrylic/urethane copolymer; 21.5% whitening agent; 1.6% thickening agent;
1.3% defoaming agent; and 2.5% cross-linking agent.
acrylic/urethane copolymer; 21.5% whitening agent; 1.6% thickening agent;
1.3% defoaming agent; and 2.5% cross-linking agent.
25. The construction of Claim 16, wherein said backcoating consists initially of the following constitutents:
(a) a water-borne mixture of an acrylic/urethane copolymer in a proportion from about 69 percent to about 80 percent;
(b) a whitening agent in a proportion from about 21 percent to about 24 percent;
(c) a defoamer in a proportion from about 0.4 percent to about 0.6 percent;
(d) an acrylic-based thickening agent in a proportion from about 1.5 percent to 2.5 percent; and (e) a pH-adjusting agent in a proportion up to about 0.3 percent.
(a) a water-borne mixture of an acrylic/urethane copolymer in a proportion from about 69 percent to about 80 percent;
(b) a whitening agent in a proportion from about 21 percent to about 24 percent;
(c) a defoamer in a proportion from about 0.4 percent to about 0.6 percent;
(d) an acrylic-based thickening agent in a proportion from about 1.5 percent to 2.5 percent; and (e) a pH-adjusting agent in a proportion up to about 0.3 percent.
26. The construction of Claim 16 wherein said backcoating initially consists of the following constituents:
(a) a water-borne polymeric acrylic system in a proportion from about 42 percent to about 62 percent;
(b) water in a proportion from about 2 percent to about 12 percent;
(c) an anti-skinning agent in a proportion from about 1.5 percent to about 2.5 percent;
(d) a whitening agent in a proportion from about 5 percent to about 36 percent;
(e) a flatting agent in a proportion from about 3 percent to about 5 percent;
(f) a pH-adjusting agent in a proportion from about 0.3 percent to about 0.5 percent;
(g) a defoamer in a proportion from about 0.6 percent to about 1.0 percent;
(h) a coalescent solvent in a proportion from about 1.0 percent to 1.6 percent; and (i) a thickener in a proportion from 0 percent to 3.8 percent.
(a) a water-borne polymeric acrylic system in a proportion from about 42 percent to about 62 percent;
(b) water in a proportion from about 2 percent to about 12 percent;
(c) an anti-skinning agent in a proportion from about 1.5 percent to about 2.5 percent;
(d) a whitening agent in a proportion from about 5 percent to about 36 percent;
(e) a flatting agent in a proportion from about 3 percent to about 5 percent;
(f) a pH-adjusting agent in a proportion from about 0.3 percent to about 0.5 percent;
(g) a defoamer in a proportion from about 0.6 percent to about 1.0 percent;
(h) a coalescent solvent in a proportion from about 1.0 percent to 1.6 percent; and (i) a thickener in a proportion from 0 percent to 3.8 percent.
27. The construction of Claim 16 wherein said backcoating initially consists of the following constituents:
(a) a water-borne mixture of an acrylic/urethane copolymer in proportion from about 70 percent to about 90 percent;
(b) a whitening agent in a proportion from about 10 percent to about 20 percent;
(c) a defoamer in a proportion from about 0.3 percent to about 0.6 percent;
(d) a pH adjusting agent in a proportion up to about 0.3 percent; and (e) an aqueous solution of a cross-linking agent in a proportion from about 0.9 percent to about 1.5 percent, by weight, of constituents (a)-(d).
(a) a water-borne mixture of an acrylic/urethane copolymer in proportion from about 70 percent to about 90 percent;
(b) a whitening agent in a proportion from about 10 percent to about 20 percent;
(c) a defoamer in a proportion from about 0.3 percent to about 0.6 percent;
(d) a pH adjusting agent in a proportion up to about 0.3 percent; and (e) an aqueous solution of a cross-linking agent in a proportion from about 0.9 percent to about 1.5 percent, by weight, of constituents (a)-(d).
28. The construction of Claim 1, further including a lamina of flexible thermoplastic material co-extensive with and secured to said light-receiving and transmitting side of said thermoplastic web, said lamina including means for absorbing radiation in about the ultraviolet range.
29. The construction of Claim 28 wherein said lamina is formed from polymethyl methacrylate in a thickness from about 0.2 mil to 0.4 mil.
30. The construction of Claim 28 wherein said lamina is formed from a rubber-based cross-linked thermoplastic acrylic polymer composition, and said absorbing means is 2-(2H-benzotriazol-2-yl)-4-methyl-phenol.
31. The construction of Claim 30 wherein said lamina is from about 0.5 mil to about 2.0 mil in thickness.
32. A retroreflective cube corner laminate sheet construction comprising;
a thermoplastic web having a light-receiving and transmitting first side, and a second side coextensive with said first side;
said second side having a repeating retroreflective cube corner pattern formed on at least a portion thereof;
a layer of hydrophobic granular material disposed on said second side to cover selected portions of said formed cube corner pattern and leaving remaining area of said second side devoid of said hydrophobic granular material;
a layer of backcoating material deposited on said second side to overlay said hydrophobic granular material;
said backcoating material also contacting substantially all of said remaining area of said second side devoid of said hydrophobic granular material;
the particle size of said hydrophobic granular material being such that the area in which it is deposited will be effectively impervious to said backcoating material, whereby said backcoating material is unable to penetrate said granular material and interact with said second side except in said remaining area devoid of said granular material;
said backcoating material being in secure attachment to said second side at said remaining area, thereby encapsulating said granular material between said second side and said backcoating material;
a layer of adhesive applied to and generally co-extensive with said backcoating material; and a release sheet releasably secured to said adhesive layer.
a thermoplastic web having a light-receiving and transmitting first side, and a second side coextensive with said first side;
said second side having a repeating retroreflective cube corner pattern formed on at least a portion thereof;
a layer of hydrophobic granular material disposed on said second side to cover selected portions of said formed cube corner pattern and leaving remaining area of said second side devoid of said hydrophobic granular material;
a layer of backcoating material deposited on said second side to overlay said hydrophobic granular material;
said backcoating material also contacting substantially all of said remaining area of said second side devoid of said hydrophobic granular material;
the particle size of said hydrophobic granular material being such that the area in which it is deposited will be effectively impervious to said backcoating material, whereby said backcoating material is unable to penetrate said granular material and interact with said second side except in said remaining area devoid of said granular material;
said backcoating material being in secure attachment to said second side at said remaining area, thereby encapsulating said granular material between said second side and said backcoating material;
a layer of adhesive applied to and generally co-extensive with said backcoating material; and a release sheet releasably secured to said adhesive layer.
33. The construction of Claim 32 wherein said hydrophobic granular material is deposited on said second side so as to form a regular and repeating array.
34. The instruction or Claim 33 wherein said array, includes discrete, regularly-spaced pattern elements of selected geometric shape; and each said pattern element is surrounded by contiguous portions of said second side devoid of said hydrophobic granular maternal.
35. The construction of Claim 33 wherein said array comprises an array of square pattern elements;
said pattern elements defining therebetween a series of paths devoid of said hydrophobic granular material.
said pattern elements defining therebetween a series of paths devoid of said hydrophobic granular material.
36. The construction of Claim 32 wherein said backcoating material is applied to substantially completely overlay said hydrophobic granular material and said remaining area of said formed pattern.
37. The construction of Claim 32 wherein said hydrophobic granular material has a particle size of about 18 nanometers.
38. The construction of Claim 32 wherein said hydrophobic granular material is hydrophobic silica.
39. The construction of Claim 32 wherein said backcoating includes a major proportion of a water-borne acrylic-urethane copolymer.
40. The construction of Claim 32 wherein said backcoating includes a major proportion of a polymeric acrylic water-borne system.
41. The construction of Claim 32 wherein said backcoating initially includes a hydrophobic granular material,a polar solvent, and a non-polar solvent.
42. The construction of Claim 41 wherein said hydrophobic granular material is hydrophobic silica.
43. The construction of Claim 41, wherein said polar solvent is an aliphatic alcohol.
44. The construction of Claim 41, wherein said polar solvent is butanol.
45. The construction of Claim 41, wherein said non-polar solvent comprises mineral spirits.
46. The constuction of Claim 41, wherein said polar solvent is present in an amount from about 15% to about 30% of said slurry and said non-polar solvent is present in an amount from about 40% to about 70%.
47. The construction of Claim 32, further including a lamina of flexible thermoplastic material co-extensive with and secured to said light-receiving and transmitting side of said thermoplastic web, said lamina including means for absorbing radiation in about the ultraviolet range.
48. The construction of Claim 47 wherein said lamina is formed from polymethyl methacrylate in a thickness from about 0.2 mil to 0.4 mil.
49. The construction of Claim 47 wherein said lamina is formed from a rubber-based cross-linked thermoplastic acrylic polymer composition, and said absorbing or blocking means is 2-(2H-benzotriazol-2-yl)-4-methyl-phenol.
50. The construction of Claim 47 wherein said lamina is from about 0.5 mil to about 2.0 mil in thickness.
51. A method for producing a cube corner type retroreflective laminate sheet construction, said method comprising the steps of:
(a) applying to a web of thermoplastic material having a retroreflective cube corner formed pattern on at least a portion of one side, a layer of hydrophobic granular material deposited so as to form a regular and repeating array on said retroreflective pattern;
(b) forming, as part of said array a plurality of paths on said one side devoid of said hydrophobic granular material;
(c) applying a layer of backcoating material to overlay said hydrophobic granular material and to fill said paths;
(d) selecting the particle size of said hydrophobic granular material to such that the area in which it is deposited will be effectively impervious to said backcoating material whereby said backcoating material is unable to penetrate said granular material and interact with said second side except in the area devoid of said granular material; and (e) adhering said backcoating material to encapsulate said hydrophobic granular material between said formed side and said backcoating material.
(a) applying to a web of thermoplastic material having a retroreflective cube corner formed pattern on at least a portion of one side, a layer of hydrophobic granular material deposited so as to form a regular and repeating array on said retroreflective pattern;
(b) forming, as part of said array a plurality of paths on said one side devoid of said hydrophobic granular material;
(c) applying a layer of backcoating material to overlay said hydrophobic granular material and to fill said paths;
(d) selecting the particle size of said hydrophobic granular material to such that the area in which it is deposited will be effectively impervious to said backcoating material whereby said backcoating material is unable to penetrate said granular material and interact with said second side except in the area devoid of said granular material; and (e) adhering said backcoating material to encapsulate said hydrophobic granular material between said formed side and said backcoating material.
52. The method of Claim 51 further including the step of:
(f) securing an overlayer of weather-resistant thermoplastic material, containing absorbers of radiation in about the ultra-violet range, to that side of said web opposite to the side on which said cube corner type pattern is formed.
(f) securing an overlayer of weather-resistant thermoplastic material, containing absorbers of radiation in about the ultra-violet range, to that side of said web opposite to the side on which said cube corner type pattern is formed.
53. The method of Claim 51, interposing between steps (b) and (c) the step of:
(b1) drying said layer of hydrophobic granular material.
(b1) drying said layer of hydrophobic granular material.
54. The method of Claim 51, wherein said hydrophobic granular material is hydrophobic silica.
55. The method of Claim 51, wherein substantially the entire second side is formed to contain cube corner elements therein and said backcoating adheres directly to portions of said cube corner elements devoid of said hydrophobic granular material.
56. A method for producing a cube corner type retroreflective laminate sheet construction, said method comprising the steps of:
(a) applying a layer of hydrophobic granular material to a web of thermoplastic material having a retroreflective cube corner formed pattern on at least a portion of one side, said granular material deposited so as to form a regular and repeating array on said retroreflective pattern;
(b) forming, as part of said array a plurality of paths on said one side devoid of said hydrophobic granular material;
(c) applying a layer of backcoating material to overlay said hydrophobic granular material and to fill said paths; and (d) adhering said backcoating material to encapsulate said hydrophobic granular material between said formed side and said backcoating material;
the particle size of said hydrophobic granular material being such that the area in which it is deposited will be effectively impervious to said backcoating material whereby said backcoating material is unable to penetrate said granular material and interact with said second side except in the area devoid of said granular material.
(a) applying a layer of hydrophobic granular material to a web of thermoplastic material having a retroreflective cube corner formed pattern on at least a portion of one side, said granular material deposited so as to form a regular and repeating array on said retroreflective pattern;
(b) forming, as part of said array a plurality of paths on said one side devoid of said hydrophobic granular material;
(c) applying a layer of backcoating material to overlay said hydrophobic granular material and to fill said paths; and (d) adhering said backcoating material to encapsulate said hydrophobic granular material between said formed side and said backcoating material;
the particle size of said hydrophobic granular material being such that the area in which it is deposited will be effectively impervious to said backcoating material whereby said backcoating material is unable to penetrate said granular material and interact with said second side except in the area devoid of said granular material.
57. The method of Claim 56 wherein said layer of hydrophobic granular material consists initially of a slurry comprising a hydrophobic granular material, a polar solvent, and a non-polar solvent, said polar solvent and said non-polar solvent present in relative proportions sufficient to allow deposition of said hydrophobic granular material in said well-defined array on said thermoplastic web.
58. The method of Claim 57, wherein said polar solvent is n-butanol.
59. The method of Claim 57, wherein said non-polar solvent comprises low odor mineral spirits.
60. The method of claim 57, wherein said polar solvent is present in an amount from about 10% to about 30% of said slurry, and said non-
60. The method of claim 57, wherein said polar solvent is present in an amount from about 10% to about 30% of said slurry, and said non-
Claim 60 - cont'd ...
polar solvent is present in an amount from about 40% to about 70% of said slurry.
polar solvent is present in an amount from about 40% to about 70% of said slurry.
61. The method of Claim 57, wherein said polar solvent is present in an amount of about 15% of said slurry.
62. The method of Claim 57, wherein said slurry consists of from about 15% to about 35% of said hydrophobic granular material, from about 10% to about 30% of said polar solvent, and from about 40% to about 70% of said non-polar solvent.
63. The method of Claim 57, wherein said slurry includes a thixotropic thickener.
64. The method of Claim 56 wherein said backcoating consists of the following constituents:
(a) a water-borne mixture of an acrylic/urethane copolymer in a proportion from about 70 percent to about 90 percent;
(b) a coloring agent in a proportion from about 6 percent to about 24 percent;
(c) a defoamer in a proportion from about 0.4 percent to about 0.9 percent;
(d) an acrylic-based thickening agent in a proportion from about 1.5 percent to about 3.5 percent;
(e) deionized water in a proportion from none to about 5 percent;
and (f) a pH-adjusting agent in a proportion from none to about 0.3 percent.
(a) a water-borne mixture of an acrylic/urethane copolymer in a proportion from about 70 percent to about 90 percent;
(b) a coloring agent in a proportion from about 6 percent to about 24 percent;
(c) a defoamer in a proportion from about 0.4 percent to about 0.9 percent;
(d) an acrylic-based thickening agent in a proportion from about 1.5 percent to about 3.5 percent;
(e) deionized water in a proportion from none to about 5 percent;
and (f) a pH-adjusting agent in a proportion from none to about 0.3 percent.
65. The method of Claim 64, wherein said backcoating includes:
(g) an aqueous solution of a cross-linking agent in a proportion from about 0.5 percent to about 1.5 percent, by weight, of constituents (a)-(d).
66. The method of Claim 56, wherein said backcoating consists of the following constituents:
(a) a water-borne polymeric acrylic system in a proportion from about 42 percent to about 62 percent;
(g) an aqueous solution of a cross-linking agent in a proportion from about 0.5 percent to about 1.5 percent, by weight, of constituents (a)-(d).
66. The method of Claim 56, wherein said backcoating consists of the following constituents:
(a) a water-borne polymeric acrylic system in a proportion from about 42 percent to about 62 percent;
Claim 66 - cont'd ...
(b) water in a proportion from about 2 percent to about 12 percent;
(c) an anti-skinning agent in a proportion from about 1.5 percent to about 2.5 percent;
(d) a coloring agent in a proportion from about 5 percent to about 36 percent;
(e) a flatting agent in a proportion from about 3 percent to about 5 percent;
(f) a pH-adjusting agent in a proportion from about 0.3 percent to about 0.5 percent;
(g) a defoamer in a proportion from about 0.6 percent to about 1.0 percent;
(h) a coalescent solvent in a proportion from about 1.0 percent to 1.6 percent; and (i) a thickener in a proportion from 0 percent to 3.6 percent.
(b) water in a proportion from about 2 percent to about 12 percent;
(c) an anti-skinning agent in a proportion from about 1.5 percent to about 2.5 percent;
(d) a coloring agent in a proportion from about 5 percent to about 36 percent;
(e) a flatting agent in a proportion from about 3 percent to about 5 percent;
(f) a pH-adjusting agent in a proportion from about 0.3 percent to about 0.5 percent;
(g) a defoamer in a proportion from about 0.6 percent to about 1.0 percent;
(h) a coalescent solvent in a proportion from about 1.0 percent to 1.6 percent; and (i) a thickener in a proportion from 0 percent to 3.6 percent.
67. The method of Claim 56, wherein said slurry includes a polar solvent and a non-polar solvent.
68. The method of Claim 67, wherein said polar solvent is an aliphatic alcohol.
69. The method of Claim 67, wherein said polar solvent is n-butanol.
70. The method of Claim 67, wherein said non-polar solvent comprises low odor mineral spirits.
71. A flexible cube corner type retroreflective laminate sheet construction including a retroreflective web with a light-receiving and transmitting first side and a second side co-extensive with said first side, and a cube corner type retroreflective pattern formed on at least a portion of said second side, said construction comprising:
a layer of hydrophobic granular material deposited on said second side to cover selected portions of said cube corner pattern, with the uncovered portions of said second side forming paths devoid of said granular material;
a layer of backcoating material deposited on said second side to overlay said hydrophobic granular material, said backcoating material contacting said uncover-ed portion of said cube corner pattern on said second side and being fixedly secured thereto, thereby encapsulating said granular material between said second side and said backcoating layer, the particle size of said hydrophobic granular material being such that the area in which it is deposited will be effectively impervious to said backcoating material wherein said backcoating material is unable to penetrate said granular material and interact with said second side pattern except in said uncovered portions; and means for adjusting the amount of incident light reflected from said first side of said retroreflective web, without changing said formed cube corner pattern on said second side.
a layer of hydrophobic granular material deposited on said second side to cover selected portions of said cube corner pattern, with the uncovered portions of said second side forming paths devoid of said granular material;
a layer of backcoating material deposited on said second side to overlay said hydrophobic granular material, said backcoating material contacting said uncover-ed portion of said cube corner pattern on said second side and being fixedly secured thereto, thereby encapsulating said granular material between said second side and said backcoating layer, the particle size of said hydrophobic granular material being such that the area in which it is deposited will be effectively impervious to said backcoating material wherein said backcoating material is unable to penetrate said granular material and interact with said second side pattern except in said uncovered portions; and means for adjusting the amount of incident light reflected from said first side of said retroreflective web, without changing said formed cube corner pattern on said second side.
72. The construction of Claim 50 wherein said reflection adjusting means includes sizing and shaping said paths to cover a selected portion of the surface area of said cube corner pattern found in said second web side.
73. The construction of Claim 72 wherein said hydrophobic granular material is deposited so as to form a regularly-spaced array of discrete pattern elements, each said pattern element being surrounded by contiguous portions of said paths.
74. The construction of Claim 73 wherein said pattern elements are square.
75. The construction of Claim 73 wherein each said pattern element is a square having sides of 0.200 inch and each said path is 0.015 inch wide.
76. The construction of Claim 73 wherein each said pattern element is a square having sides of 0.138 inch wide and each said path is 0.127 inch wide.
77. The construction of Claim 73 wherein each said pattern element is a square having sides of 0.096 inch and each said path is 0.029 inch wide.
78. The construction of Claim 71 and 72 wherein said paths define rectangular pattern elements.
79. The construction of Claim 72 including a lamina co-extensive with and secured to said first side of said retroreflective web, said lamina including means to absorb radiation in about the ultraviolet range on said retroreflective web.
80. The construction of Claim 79 wherein said lamina is formed of polymethyl methacrylate in a thickness of about 0.2 mil to about 0.40 mil.
81. The construction of Claim 79 wherein said lamina is formed from a rubber-based, cross-linked thermoplastic acrylic polymer composition.
82. The construction of Claim 79 wherein said absorbing means is 2-(2H-benzotriazol-2-yl)-4-methyl-phenol.
83. The construction of Claim 1, 32 or 71, wherein substantially the entire second side is formed to contain cube corner elements therein and said backcoating adheres directly to portions of said cube corner elements devoid of said hydrophobic granular material.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US53306883A | 1983-09-19 | 1983-09-19 | |
| US533,068 | 1983-09-19 | ||
| US64000984A | 1984-08-10 | 1984-08-10 | |
| US640,009 | 1984-08-10 |
Related Child Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000586270A Division CA1276046C (en) | 1983-09-19 | 1988-12-16 | Retroreflective sheeting and methods for making same |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1247423A true CA1247423A (en) | 1988-12-28 |
Family
ID=27064048
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000463618A Expired CA1247423A (en) | 1983-09-19 | 1984-09-19 | Retroreflective sheeting and methods for making same |
| CA000586270A Expired - Fee Related CA1276046C (en) | 1983-09-19 | 1988-12-16 | Retroreflective sheeting and methods for making same |
Family Applications After (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000586270A Expired - Fee Related CA1276046C (en) | 1983-09-19 | 1988-12-16 | Retroreflective sheeting and methods for making same |
Country Status (1)
| Country | Link |
|---|---|
| CA (2) | CA1247423A (en) |
-
1984
- 1984-09-19 CA CA000463618A patent/CA1247423A/en not_active Expired
-
1988
- 1988-12-16 CA CA000586270A patent/CA1276046C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| CA1276046C (en) | 1990-11-06 |
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