CA2218712A1

CA2218712A1 - Retroreflective sheet and article having retroreflectiveness

Info

Publication number: CA2218712A1
Application number: CA002218712A
Authority: CA
Inventors: Yoshinori Araki; Masami Yokoyama
Original assignee: Individual
Current assignee: 3M Co
Priority date: 1995-05-12
Filing date: 1996-04-22
Publication date: 1996-11-14
Also published as: CN1185211A; EP0824711B1; ATE196366T1; AU5567296A; CN1095082C; KR100380677B1; US5714223A; JP3493245B2; JPH08314399A; AU697421B2; ES2150121T3; MX9708444A; WO1996035969A1; DE69610303T2; KR19990014695A; EP0824711A1; RU2160913C2; DE69610303D1

Abstract

A retroreflective article that comprises: (a) a retroreflective layer having first and second major surfaces; and (b) a cover layer juxtaposed against the first major surface, characterized in that: the cover layer comprises a surface layer, an optional intermediate layer, and a back layer, with the provisos that: (i) when the intermediate layer is present in the cover layer the intermediate layer contains a vinylidene fluoride base polymer as a primary component, and the surface layer and back layer each comprise a methyl methacrylate base polymer as a primary component; and (ii) when the intermediate layer is absent from the cover layer, the surface layer comprises a methyl methacrylate base polymer (A) and a vinylidene fluoride base polymer (F) in a weight ratio A:F of 55:45 to 95:5, and the back layer comprises a methyl methacrylate base polymer and a vinylidene fluoride base polymer with the vinylidene fluoride base polymer being the primary component.

Description

W 096/35969 PCTrUS96/05629 RETROREFLECTIVE SHEET AND
ARTICLE HAVING RETROREFLECTIVENESS

Teçhnic~l Field 5 The present invention relates to an improvement of a rellorenective sheet.
In particular, the present invention relates to a rtl~olenective sheet that is bonded to an article such as a plate of a traffic sign, a plate of a guidepost and so on, to impart the relrolenectiveness to the article. Further, the present invention relates to such article having the r~ll ol c;nectiveness.
Background With a traffic sign or a guidepost, a l ell or~nective sheet ~lt~ ing a r~llolenective propel ly, that is, a property of reflecting a light beam in a direction reverse to a direction of light incidçnce, is widely used.
As such sheet, there are known an enclosed lens l ell ol enective sheet (disclosed in, for example, JP-A-5-131589, etc.), an encapsulated lens type lellolt;nective sheet (disclosed in, for example, JP-A-3-9837, etc.), a prismatic rellolenective sheet (disclosed in, for ~Y~mple, JP-A-60-100103, etc.), and so on.
While these l~llult;nective sheets (hereinafter referred to as "reflective sheet"
sometimes) have di~l~;lll structures ofthe rel.urenective layer, they have a coating layer on the lc;llorenective layer to protect the latter. As the coating layer, a resinous film having light tran~,arenc~y is known.
As the resinous film to be used as the coating layer, the following films are known:
For example, from JP-B-40-7870, JP-A-52-21793, ~lP-A-52-110592, JP-A-60-194405 and JP-A-2-196653, there are known reflective sheets having a coating layer made of a film which ç~nti~lly concicl ~ of a single layer of an ac~ylic polymer (e.g. polymethyl meth~-.rylate, etc.), a polyester polymer (e.g. polycarbonate, polyethylene terephth~l~te, etc.), a cellulose ester polymer (e.g. cellulose acetate, etc.), and the like. Among them, the acrylic polymer is used when the reflectivesheet is used outdoors since it has good weatherability. But, since the single layer W 096/35969 PCT/US96/0~629 film of the acrylic polymer is relatively rigid and fragile, its impact recict~nce is low.
In the case of a reflective sheet which has been processed by cutting or pl-nr~hing out in a determined size and shape and adhered to an article, the coating layer is broken from the processed edge parts as if it were chipped, and finally, the breakage S often extend to the lGLlulenective layer. To express a degree of rçeict~nr.e to the breakage of edge parts, a term "rÇcict~nce to edge Chlpping" will be used.
As disclosed in JP-A-61-255846, a reflective sheet is known, which uses, as a coating layer, a film of an acrylic polymer CGlll~liSillg an acrylic multi-phase interpolymer blend which is one of the acrylic polymer having improved impact recict~nce However, such film cannot improve the impact resiet~nce and recict~n~e to edge chipping at a s~tief~ctory level.
As disclosed in JP-A-63-307940, a reflective sheet is known, which uses, as a coating layer, a film of an ionomer or an ethylene base copolymer such as an ethylene-acrylic acid copolymer. While such film has practically s~ticf~ctQry impact resistance and ~e;~ ce to edge chipping, it suffers from decrease of weathera-bility, in particular, film coloring caused by ultraviolet ray.
As disclosed in JP-A-6-138312, a reflective sheet is known, which uses, as a coating layer, a film of a fluoropolymer such as polyvinylidene fluoride. This film is excellent in impact recict~nce and resict~n.;e to edge chipping and has a property that its surface is hardly stained. But, since this film has low adhesion to thele~lu,enective layer and a print layer formed on the coating layer, abrasion loss of the print layer or d~l~min~tion of the coating layer from the lellOleneCtiVe layer happen, and then the practical durability of the sheet is low.
A surface protective film comprising both the fluoropolymer such as polyvinylidene fluoride and the acrylic polymer such as polymethyl meth~-~.rylate is disclosed in several publications, for cA~llple, JP-B-56-51907, JP-A-57-142359, JP-A-57-187248, JPA-58-205764, JP-B-61-29874, JP-A-1-262133, JP-A-2-72945, JP-A-3-124754, JP-A-3-288640, and JP-A-6-80794. The disclosed films are (i) A blend film comprising a fluoropolymer as a primary component and an acrylic polymer as a secondary component, W 096t35969 PCTrUS96/05629 (ii) A l~min~te film comprising outer surface layers which consist esc~nti~lly of a fluoropolymer and an inner layer which co~ s eceçnti~lly of an acrylic polymer and is not exposed outside, (iii) A 1~ ;nA~e film comprising outer surface layers of a blend films which S comprises a fluoropolymer as a primary con.ponc ll and an acrylic polymer as a secondary polymer, and an inner layer of a blend film which comprises an acrylicpolymer as a primary colllpollelll and a fluoropolyrner as a secondary component.
Since the fluoropolymer such as polyvinylidene fluoride has high pare~ y and does not have an abso-l,ance wavelength in the W light range, it has eYcPllçnt weatherability. In addition, since it has relatively high flexibility, it is suitable for use in a place where impact rçeiet~nce is required. For ~Y~mple7 it is used as a surface protective film of an article made of plastics, rubbers, metals, glass or wood.
The outer surface layer of the surface p~ e~ e film C~JnlaillS, as a primary con~pollell~, the fluoropolymer to improve the stain-proofing property of the film surface. When such surface protective film is used as a coating layer of the reflective sheet, adhesion of the surface layer of the coating layer to the rcl. o. cnec-tive layer and the print layer is poor, and therefore, the practical durability of the sheet cannot be improved. Further, the above surface protective film has inferior reciet~nce to edge chipping to the film of the fluoropolymer alone. Then, the improvement of reCiet~n.-e to edge chipping is desired. In particular, in the case of a reflective sheet which is used on a plate of a trafflc sign, a plate of a guidepost and so on together with a print layer formed thereon, the above improvement is immet1i~tely required.
An object ofthe present invention is to provide a lellorcnective sheet which has good adhesion of a coating layer to a rcL.oleflective layer and a coating layer and therefore good practical durability, and is excellent in impact reciet~nre and weatherability as well as recict~nce to edge chipping.
Another object of the present invention is to provide an article having a .~I.Olcnectiveness as one of the p.erc.. ed applications of such ~ -urenective sheet.

W 096/3S969 PCT~US96/05629 According to a first aspect of the present invention, there is provided a ~l,or~nective sheet cor,-~,isi"g a ~ ol~nective layer which l~llolenects a lightbeam which is i~ ted from one of major surfaces of the l~llul~;llective layer, and a coating layer coated on said one of major s~lrf~c~, characterized in that said coating layer cGlllpl;ses a surface layer and a back layer which is present on a side facing said one of major surfaces, and said surface layer comprises a methyl meth~-.rylate base polymer (A) and a vinylidene fluoride base polyrner (F) in a weight ratio (A:F) offrom 55:45 to 95:5.
In this first invention, since the coating layer comprises a surface layer and aback layer which is present on a side facing one of the major surfaces of the rellult;nective layer, and the surface layer comprises a methyl mPth~çrylate base polymer (A) and a vinylidene fluoride base polymer (F) in a weight ratio (A:F) of from 55:45 to 95:5, the coating layer has good adhesion to the rellulenective layer and the print layer formed on the surface layer and thel erol e good practical durability and the r~l,ult:flective layer is excellent in r~ist~n~e to edge chil)pillg.
When the content of the methyl methacrylate base polymer is smaller than the above range, the adhesion of the coating layer to the reflective layer and the coating layer is wul~ened. When, the content of the methyl ~ h~.~ylate base polymer is larger than the above range, the recict~nce to edge chipping is deteriorated.
Since the back layer is provided between the surface layer of the coating layer and the lellc,lc;nective layer, the rÇci~t~nce to edge chipping is improved in cooperation with the effect of the weight ratio of the polymers in the surface layer.
According to a second aspect of the present invention, there is provided a l t:LI ul enective sheet comprising a I ell Ol ~nective layer which I ~ll Ol enects a light beam which is illllmin~ted from one of major surfaces of the lellol~nective layer, and a coating layer coated on said one of major surfaces, characterized in that said coating layer comprises, in this order, a surface layer, an intermediate layer and a back layer which is present on a side facing said one of major surfaces, said surface layer comprises a methyl meth~crylate base polymer as a primary component, and said intermedi~te layer comprises a vinylidene fluoride base polymer as a plhllaly component.
In this second invention, since the coating layer comprises, in this order, a surface layer, an h~lel~e~ e layer and a back layer which is present on a side facing said one of major surfaces, the surface layer comprises a methyl m~th~crylate base polymer as a primary COlllI~OnGIII, and the interme~ te layer colll}~lises a vinylidene fluoride base polymer as a pl;lllaly component, the coating layer hasgood adhesion to the leLlorenective layer and the print layer formed on the surface layer and ~hert;role good practical durability, and the leLlol~;nective layer isexcellent in resict~nce to edge chipping.
Since the back layer is provided between the surface layer of the coating layer and the l~Llolenective layer, the rÇcict~n~e to edge chipping is improved in cooperation with the effect achieved by the structure having the surface layer and the interme~i~te layer.
It is pr~rt;lled for further improvement of the recict~nce to edge chipping to form the interme~ te layer from the methyl meth~crylate polymer (A) and the vinylidene fluoride base polymer (F) in a weight ratio of from 5 :95 to 45 :55.
In the second invention, the formation of the surface layer from the methyl meth~crylate polymer (A) and the vinylidene fluoride base polymer (F) in a weight ratio of from 55:45 to 95:5 further increases the rçcict~nce to edge chipping while further improving the adhesion of the coating layer to the print layer.
In the first and second inventions, the formation of the back layer from the methyl meth~çrylate polymer (A) and the vinylidene fluoride base polymer (F) in a weight ratio of from 55:45 to 95:5 enables the formation of the print layer withgood adhesion on the side of the back layer which side is l~min~ted on the re~,o~enective layer in addition to the further improvement of the adhesion to the rello~nective layer and the resict~nce to edge chipping.
The above coating layer is excellent also in impact recict~nce and weatherability, since it cc lllplises a blend layer co..l~ ;..g the methyl mPth~crylate base polymer and the vinylidene fluoride base polymer, or a l~min~te of a layer comprising the methyl meth~crylate base polymer as the primary component and a W 096/35969 PCT~US96/05629 layer comprising the vinylidene fluoride base polymer as the plhll~LIy component, or both of the blend layer and the l~min~te It is plerellcd for the coating layer to have a tran~miCsi~ n to all light of atleast 90 % for the purpose of increasing a reflection l~ AI-~e and stability of the reflection Illmin~nce with time (retention of reflection l~ ;l1A~
When the reflective sheet of the first and second invention is an ~n~Ars~ ted lens rt;ll ul t;nective sheet having a retl o, enective layer which colll~lises lens means made of plural ll~nS~ elll microspheres, a support Illt;lllbel in which the lens means is partly embedded, a bonding layer having plural linking parts which are bonded to the coating layer so that spaces for encaps~ ting the sl)a,~n~ microspheres are formed between the coating layer and the bonding layer, and reflectors which are present with cont~ctinf~ the lens means, the rçci~tAnce to edge chipping which is particularly i,nl,ol L~"l in the ~nc~rslll~ted lens leLIolenective sheet is improved, and the It;L~urenective sheet has good adhesion of the coating layer to the 1 ell Ol t;nective layer and the print layer and is excellent in the impact recict~nre and weatherability so that the sheet has good practical durability.
When the iellolt;nective sheet of the first or second invention is used in an article comprising an article body and a lel~ult;nective sheet which is processed by cutting or plln~hin~ out in a desired size and shape and adhered to the article body with adhering means such as an article used outdoors, for example, a plate of a traffic sign, a plate of a guidepost and so on, the above described good practical properties of the sheet can be i",pa, Led to the article.
Components of the ,t:l,ol~nective sheet of the present invention will be ~Ypl~ined further in detail Retroreflective Layer As the re~, o, t:nective layer, one of the following l ~;LI ul enective layer may be p, t;rt;, ~Iy used:
(a) "An encapsulated lens Ic:~ult;nective layer" which comprises lens means made of plural Ll ~n~alenl microspheres 3, a support member 7 in which thelens means is partly embedded, a bonding layer 5 having plural linking parts 8 which W O 96/35969 PCT~US96/05629 are bonded to the coating layer 1 so that spaces 2 for encaps~ ting the llal1:,palenl microspheres are formed between the coating layer and the bonding layer, and reflectors 4 which are present with cont~cting the lens means, and is used in the enc~rslll~te~l lens rt;L.or~;nective sheet, as shown in Fig. 1. In Fig. 1, numeral 6 stands for an adhesive layer.
(b) "A prismatic ~ ol~nective layer" which compl;ses a prism member 22 having a flat surface and plural tri~n~l~r protrusions for reflecting the int~idçnt light back to the inrident direction, on a surface opposite to the flat surface, and is used in the plisllldlic rtillul~nective sheet as shown in Fig. 2, which comprises a coating layer 21, a prism member 22, a coloring layer 23, a primer layer 24, an adhesivelayer 25, and a releasing layer 6 (e.g. a liner or a release paper).
(c) "An enclosed lens rellolc;nective layer" which comprises lens means made of plural transparent microspheres, a resinous layer in which the lens means is wholly embedded and which is adhered to the coating layer on s~s~ y its whole surface, and reflectors which are present at a certain ~ t~nce from the lens means, and is used in an enclosed lens I t:llolellective sheet.
Among them, the lt;llolenective layers (a) and (b) are prere.led since a relatively high reflection Illmin~nce and good retention of the reflection Inmin~nce are easily achieved. In view of the easy production of the highly flexible reflective sheet, the I c;ll Ol t;nective layer (a) is pl c:rel I ~d. The high flexibility of the reflective sheet prevents peeling off of the reflective sheet from its edge when the sheet is adhered to an article an edge of which is bent to have a round edge such as the traffic sign plate.

T- ~In:~lJdl t~ Microspheres As the ll~llslJ~lelll microspheres, glass beads or plastic beads having a desired refractive index may be used, a desired refractive index is usually from 1.4 to 2.7.
When the l~Llor~nective layer is the encapsulated lens lc;llor~nective layer (a), the refractive index is p-~;reldbly from 1.6 to 2.3. When the refractive index is outside this range, the le~l~,r~nectiveness may be lost. That is, an amount of light W O 96/35969 PCTrUS96/05629 which is I~L~o,enected in the direction of the incidçnt light is decreased, while an angle of observation of the reflected light is widened. Widening of the angle ofobservation to some extent may be used in a ~el,ur~lective sheet of a wide angle of observation type, which widens the angle of obsc~ alion with ~ p the reflection hlmin~nre in an acceptable range. However, if the angle of observation is too large, the reflection Illmin~nce is decreased to â practically u"p,ere"ed level.
Then, the more pl~ ed refractive index is in the range belweell 1.9 and 2.1.
When the le;llult;nective layer is the enclosed lens ,t;l.o,enective layer (c), the refractive index of the microspheres is pl~r~l~bly at least 2.0, more pl ere, ably at least 2.1. When the refractive index is too small, since the rli~t~nre between the Il an~l,arel,~ microspheres and the reflection layer should be made large, it is difficult to decrease a total thickness of the reflective sheet. Theoretically, if the ~. ~nspa~
microspheres having the refractive index of about 2.8 were used, the transparentmicrospheres and the reflection layer could be placed very closely. However, it is hardly possible to produce microspheres having such high refractive index.
A di~mptrr of the microsphere is usually from 10 to 200 llm, preferably from 20 to 150 ~m, more pl~r~l~bly from 25 to 80 ~lm. When the diameter is too small, it is difficult to produce microspheres having a uniform .l;~."~l~r and aullirollll refractive index, and the reflection Illmin~nr,e of the reflective sheet comprising such microspheres tends to decrease and the ,t;~,u,t;nectiveness tends to deteriorate. When this ~ metrr is too large, the thickness of the reflective sheet may increase, and for c ~a~llple, it may be difflcult to prevent the peeling off of the reflective sheet from the round edge of the article.
Two or more kinds of the ll~ns~Jalt;lll microspheres having difI~lelll refractive indexes may be used in co~ alion, or two or more types of the l,~nsp~relll microspheres having dirrt;lell~ metrrs may be used in conlbilla~ion.
When the ~lallspal~ microspheres are colored by a colorant with ;,.;,.g the light ~l~lls~alel~cy, reflected light has a dirrelelll color from that of the inri~.nt light.

W 096/35969 PCTrUS96/05629 Prism Member The prism member of the prismatic leL,u,enective layer (b) comprises a flat surface through which the inr.;~çnt light enters, and plural tri~n~llAr pyramid lemrnte which totally reflect the inci(lçnt light effectively in the direction reverse to the incident direction. The prism memher is p,er~,~bly made of a polycarbonate resin, an ionomer resin or an acrylic resin, in view of ~.~e~ .;C~ n~,lh~ light rPflect,Ance, and so on. To provide good rel~orenectiveness and a wide angle of observation, a length of one side of the bottom of each tri~An~llAr pyramid is preferably from 0.1 to 3.0 mm. A th:A~n~e~ ofthe prism m~mb~r, namely a rliet~nce from the top of the pyramid to the flat surface is preferably from 50 to 500 ~m.When this thickness is less than 50 ~lm, the mer.h~nic~l strength is decreased, and the height of the tri~nEul~r pyramid may not reach the desired value, so that the r~L,ul~nectiveness is decreased. When this thickness is larger than 500 ~lm, thetotal thickness of the reflective sheet is too large, so that it may be difficult to prevent the peeling off of the reflective sheet from the round edge of the article.
The prismatic r1L,ort;nect*e sheet may co",p.;se, below the prism member, a coloring layer, a primer layer, an adhesive layer and a releasing layer as shown in Fig. 2.

Bondin~c Layer The bonding layer of the encapsulated lens ,eL,or~nective layer comprises a support ",e",ber in which the lens means, namely plural Ll~lsl)~lenL microspheres are partly embedded, and plural linking parts which are bonded to the coating layer so that spaces for encaps~ tinE the Ll~ns~arellL microspheres are formed betweenthe coating layer and the bonding layer.
The bonding layer comprises at least one polymer se1ected from polyuretllAn~e, acrylic polymers, polyesters, polyvinyl chloride polymers, polyvinylidene chloride polymers, polyolefins, and so on.
Preferably, the bonding layer comprises the acrylic polymer, since the acrylic polymer is excellent in weatherability, and had a large adhesion strength to theL,~l~spare,lL microspheres so that it can hold the microspheres firmly. Further, when the back layer of the coating layer comprises the methyl meth~r~rylate base polymer and the vinylidene fluoride base polymer in the above weight range, the adhesionbetween the I eLI ul enective layer and the coating layer is readily improved.
The acrylic polymer is plerel~lbly a polymer plèpaled by polynle.i~-lg a monomer co.. ~.;s;.. g an alkyl acrylate or an alkyl meth~.rylate. As the alkyl acrylate or meth~ rylate~ at least one alkyl acrylate ûr meth~crylate an alkyl group of which is one of methyl, ethyl, isoprûpyl~ butyl, isobutyl, isoûctyl~ 2-methylbutyl, 2-ethylhexyl, lauryl, stearyl, cyclohexyl, isobûrnyl, 2-hydl oAyelllyl, 2-hydl oxy~JI o~yl, 3-chloro-2-hyd. ~Ay~ro~Jyl, L"d. uAyelhoAyethyl, methoxyethyl, ethoxyethyl, dimethylaminoethyl, diethylaminoethyl and glycidyl can be used. Themonomer may additionally contain a copolymerizable monomer such as acrylic acid,methacrylic acid, 13-hydroxyethyl carboxylate, itaconic acid, maleic acid, fumaric acid, styrene, chlorostyrene, (a-methylstyrene, vinyltoluene, acrylamide, m~th~crylamide, N-methylolamide, N-methoAy---t;~l-ylacrylamide, vinyl chloride, vinyl acetate, vinyl propionate, acrylonitrile, v;.. yl~y.;dine, N,N-dimethylacrylamide, N,N-diethylacrylamide, N-acrylmorpholine, N-acrylpiperidine, and the like.
A plerelled eAa~ Jlc of the acrylic polymer is a copolymer plep&led by copolymerizing a monomer mixture comprising methyl meth~.rylate, isooctyl acrylate and ethyl acrylate.
A weight average molecular weight of the acrylic polymer is ~. erel ~bly from lO,OOOto l,OOO,OOO, moreplere.~blyfrom lOO,OOOto SOO,OOO.
The acrylic polymer may be a thermoplastic one or a curable one such as a thermosetting one or a radiation curable one. Preferably, the curable polymer, in particular, the radiation curable polymer is used. When the radiation curable polymer is used, a reactive diluent such as an acrylic monomer is added, wherebyflowability of the bonding layer before curing is easily controlled, so that theformation ofthe encapsulated lens ~eLlOlenective layer is made easy. As the result, it is possible to produce the reflective sheet having a unirollll and high reflection Illmin~nce over the whole surface of the sheet. The reflective sheet using the radiation curable polymer in the bonding layer and its production are disclosed in JPA-52-11059 (= JP-B-61-13561).

W O 9~/35969 PCT~US96/05629 A thickness of the bonding layer is usually from 10 to 200 ,um, pler~.~bly from 20 to 80 llm, more preferably from 30 to 70 llm. When the thickness of the bonding layer is too small, the impact reeiet~nce tends to decrease, and the formation of the print layer on the coating layer is difficult after the production of the reflective sheet. When the thicl~nPss of the bonding layer is too large, theflexibility of the reflective sheet may be deteriorated, and the formation of the spaces for çnc~rs~ tin~ the plural transparent microspheres may be difficult.
The bonding layer may contain, in addition to the above polymer, additives such as a pigment (e.g. rutile tit~nium ~io~cide, etc.), a polymerization initiator, a cro.e.elinkin~ agent, an antioxidant, a W light absorber, a filngi-i~le, an antiet~tiC
agent, a higher fatty acid, and so on.

Reflector As the reflector, a thin film having specular gloss, a reflective resin film co.. ~ a pearlescent pigment and the like can be used. The thin film may be formed by a thin film forming method such as vapor deposition from a metal such as ~lnmimlm, copper, silver, gold, zinc, etc. or a compound such as CeO2, Bi2O3, ZnS, TiO2, CaF2, Na3AIF6, SiO2, MgF2, etc. The reflective resin film may be forrned by coating a paint comprising a resin and a pearlescent pigment (e.g. BiOCI4, PbCO3, ~ nine obtained from fish scales, etc.) on the lens Plem~Pnt The reflector is formed with cont~ctin~ the lower half surface of each ll~nsl,arenl microsphere in the case ofthe encapsulated lens reL.olt;nective layer.
A thickness of the reflector is usually from 0.01 to 10 ~lm, preferably from 0.05 to S ,um.
The pearlescent pigment may be added to the bonding layer to increase the reflection efficiency of the reflector.

Coating Layer in the First Invention As explained above, the coating layer used in the first invention co~ ;ses the surface layer, and the back layer which is present on the side facing the one of the major surfaces of the rel-o.~;nective layer, and the surface layer comprises the W 096/3S969 PCT~US96/05629 methyl meth~çrylate base polymer (A) and the vinylidene fluoride base polymer (F) in aweight ratio offrom 55:45 to 95:5.
The "methyl m~oth~crylate base polymer" is int~nrled to mean a polymer obtained by poly~ illg a monomer colll~lisillg methyl m~th~crylate as a major component. A content of methyl ~ h~ yl~le in the monomer is preferably at least 60 % by weight, more pl~r~lably at least 90 % by weight. When the content of themethyl meth~r.rylate in the monomer is less than 60 % by weight, the colll~ibility between the methyl m.oth~çrylate base polymer and the vinylidene fluoride polymer is decreased so that the re~i~t~nce to edge chll)pil* tends to deteriorate, and the adhesion of the coating layer to the le~ort;nective layer and the print layer may be WOI ~ielled.
The monomer for the plt;para~ion of the methyl meth~çrylate base polymer may optionally contain at least one copolymerizable monomer such as a meth~r,rylate other than methyl meth~r.rylate (e.g. ethyl meth~crylate, propyl mr.th~çrylate, butyl meth~çrylate, etc.), an acrylate (e.g. methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, etc.), a fluoromonomer (e.g. vinylidene fluoride, hr~fluoropl opylene, tetrafluoroethylene, trifluorochloroethylene, etc.), and so on.
The methyl methacrylate base polymer may be a graft copolymer comprising a backbone polymer of methyl meth~r.rylate on which the above copolymerizable monomer is graft polymerized.
The "vinylidene fluoride base polymer" is int~ntled to mean a polymer prepared by polymerizing a monomer colll~lising vinylidene fluoride as a plilllaly component. A content of vinylidene fluoride in the monomer is preferably at least 60% by weight, more preferably at least 90% by weight. When the content of vinylidene fluoride in the monomer is less than 60% by weight, the colll~alibility between the methyl methacrylate base polymer and the vinylidene fluoride polymeris decreased so that the resistance to edge chipping tends to deteriorate. Further, the impact resict~nce may be deteriorated, and the reflection lllmin~nr.e may bedecreased by the decrease of the tr~n.~mic~ion of the coating layer to all light.

The monomer for the preparation of the vinylidene fluoride base polymer may optionally contain at least one copolymerizable monomer such as a fluorornnnomPr except vinylidene fluoride (e.g. h~Y~fl~ol~prc,pylene, tetrafluoroethylene, trifluorochloroethylene, etc.), a meth~f rylate (e.g. methyl mf-th~.rylate, ethyl meth~crylate, propyl meth~r.rylate, butyl meth~crylate, etc.), an acrylate (e.g. methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, etc.), and so on.
The vinyiidene fluoride base polymer may be a graft copolymer comprising a backbone polymer of vinylidene fluoride on which the above copolymerizable monomer is graft polyme,i,ed.
An average spherulite ~ meter of the vinylidene fluoride base polymer is pl~:relàbly 1.6 llm or less, more pre:rt;-ably 1.5 llm or less. When the averagespherulite di~m.o,t~r is too large, the tr~n~mi~sion of the coating layer to all light tends to decrease to, for e Aa~ , 90% or less, and then the reflection l-..n;,.~ e tends to decrease. The average spherulite diameter is measured in a film of the vinylidene fluoride base polymer by a laser small angle scattering method.
As described above, it is ees~nti~l to ~ l the weight ratio of the methyl mf~th~çrylate base polymer (A) to the vinylidene fluoride base polymer in the range between 55:45 and 9S:S. To improve the ~flheeinn of the coating layer to the lel-ort;nective layer and the print layer and the lt;s;sLance to edge cl-ipl);.. g in good b~l~nce, this weight ratio is preferably from 60:40 to 90:10, more preferably from 70:30 to 80:20.
A total content of the methyl meth~crylate base polymer and the vinylidene fluoride base polymer in the surface layer is preferably at least 80% by weight, more preferably at least 90% by weight based on the whole weight of all the polymer in the surface layer. When the total content is less than 80% by weight, the adhesion ofthe coating layer to the lc:t-orenective layer and the print layer and the resict~nce to edge chipping may be deteriorated.
As exrl~in~d above, the back layer is interposed between the rt;l-ult;nective layer and the surface layer. In general, the back layer col.. ,~.ises a polymer which has good adhesion to both the rt:~.c,lt;nective layer and the surface layer, for example, an acrylic polymer, a polyvinyl chloride polymer, a polyvinylidene chloride polymer, an ethylene-vinyl acetate copolymer and so on. Preferably, the back layer comprises the mixture of the methyl m~th~t~rylate base polymer (A) and the viny1idene fluoride base polymer (F) in the weight ratio of from 55:45 to 95:5, preferably from 60:40 to 90:10, more preferably from 70:30 to 80:20.
The methyl ...~-L~ ylate base polymer and the vinylidene fluoride base polymer in the back layer have the same m~ni~s as those used in the surface layer, and each polymer can be prepared by polyl,wl~illg the same monom~r as that used in the surface layer.
A total content of the methyl methacrylate base polymer and the vinylidene fluoride base polymer in the back layer is pl~rel~bly at least 80% by weight, more preferably at least 90% by weight based on the whole weight of all the polymer in the back layer. When the total content is less than 80% by weight, the adhesion of the coating layer to the ,t;Llor~;nective layer and the print layer and the rÇcict~n~e to edge chipping may be deteriorated, so that the print layer may not be formed with good adhesion.
A content of the vinylidene fluoride polymer in the back layer is preferably larger than that in the surface layer, whereby the rçei~t~nce to edge .,hi,)pi,lg and the impact rç~i~t~nce are further increased. In this case, the content of the vinylidene fluoride in the back layer is at least 1 (one) part by weight, preferably at least 5 parts by weight larger than that in the surface layer, based on 100 parts by weight of the polymers in each layer.
A thickness of the coating layer is preferably in the range between 10 llm and 200 ~lm, more preferably between 30 ~m and 100 ~lm. When the thickness of the coating layer is too small, the rç~i~t~nce to edge cLi~ping and the impact rçeict~nçe may be deteriorated. When this thickness is too large, the flexibility of the reflective sheet is decreased, so that it may be difficult to prevent the peeling off of the coating layer from the round edge. In the case where the reflective sheet is the ~nc~rs~ ted lens reIlective sheet, when the thiçl~n~ of the coating layer is too small, the spaces which encapsulate the plural transparent microspheres may be crushed by the dt;Ç,lll-d~ion of the coating layer caused by external force. When the thickness is too large, the linking parts of the bonding layer may not be well adhered to the back layer of the coating layer, so that the coating layer may be peeled off from the l eLI Ul t;nective layer in use.
A thickness of each layer of the coating layer is suitably selected so that the S thi~ nPcc of the whole coating is in the above range. Preferably, the thic l~nPcc of the back layer is larger than that of the surface layer, wl~el~ the lq~;c~ ce to the edge cl ipp;l,g is easily improved. In this case, the thic~npsc of the surface layer is plerel~bly from 1 to 90 ~lm, more prerelably from 3 to 25 llm, and the thi~L-ness of the back layer is pltirel~bly from 9 to 110 ~lm, more prerelably from 27 to 50 ~lm.
In the coating layer, the back layer may have two or more layers.
The coating layer can be formed by any of conventional methods of film formation. For example, the coating layer is formed in the form of a l~min~te film by melt extrusion using extrusion dies for rulllling the re~.e~iLi~e layers.
Each layer of the coating layer may contain additives such as an ~nfil~xicl~nt a W light absorber, a colorant, and so on.

Coatin~ Layer in the Second Invention The coating layer in the second invention comprises, in this order, a surface layer, an inte,..~e~ e layer and a back layer which is present on a side facing said one of major surfaces, the surface layer comprises a methyl mPfh~rrylate base polymer as a primary component, and the i"Le,...e.l;~le layer comprises a vinylidene fluoride base polymer as a primary component.
Since the i~le~...P,.l;S.Ie layer which is l~min~ted on the surface layer contains the vinylidene fluoride base polymer as the primary col,lponenL, it has a cushioning effect to absorb the external force which will break the surface layer. As the result, the recict~nce to edge chipping and the impact resict~nce are improved. Further,since the surface layer comprises the methyl mpth~crylate base polymer as the primary component, the print layer can be formed on the surface layer with good adhesion.
Since the methyl methacrylate base polymer and the vinylidene fluoride base polymer have good compatibility with each other, the surface layer and the intermediate layer can be adhered with a sufficient adhesion force for improving the resistance to edge chipping.
When the interme~ te layer contains the methyl meth~r.rylate base polymer (A) in con~ Jalion with the vinylidene fluoride base polymer ~) in a weight ratio (A:F) of from 5:95 to 45:55, more plerelably from 10:90 to 40:60, most preferably from 20:80 to 30:70, the recict~n~e to edge chipping and the impact rçcict~nce are further improved pler~l~bly.
When the surface layer colll~ins the vinylidene fluoride base polymer (F) in col,ll,il,aLion with the methyl m~th~crylate base polymer (A) in a weight ratio (A:F) of from 45:55 to 95:5, more preferably from 60:40 to 90:10, most prt;re-~bly from 70:30 to 80:20, the adhesion ofthe surface layer to the print layer and the r~cict~n~e to edge cl~ipl)ing are further improved p,c:rel~bly.
The methyl meth~crylate base polymer and the vinylidene fluoride base polymer in the back layer have the same m~ning.c as those used in the surface layer of the above çYrl~inçd first invention, and each polymer can be p,~aled by polymerizing the same monomer as that used in the surface layer of the above explained first invention.
The back layer is interposed between the interme~ te layer and the It:Ll-~l enective layer. This back layer of the second invention can achieve the same effects as those achieved by the back layer of the above explained first invention.
The structure of the back layer is preferably the same as that of the back layer of the above explained first invention.
A thickness of the coating layer is prc:rel~bly from 10 to 200 ~lm, more preferably from 30 to 100 llm by the same reason as in the first invention.
A thickness of each layer of the coating layer is suitably selected so that the thickness of the whole coating is in the above range. Pler~ bly, the thickness of the interme.li~te layer is larger than that of the surface layer or the back layer, whereby the rçcict~nce to the edge .,hi~pil-g is easily improved. In this case, the thickness of the surface layer is preferably from 1 to 60 llm, more preferably from 3 to 20 ~lm, the thickness of the interme~i~te layer is preferably from 8 to 80 ~lm, W 096/35969 PCT~US96105629 more preferably from 24 to 35 ,um, and the thickness of the back layer is preferably from 1 to 60 llm, more pl ere,ably from 3 to 20 ,um.
In the coating layer, one or both of the back layer and the interm~ te layer may comprise two or more layers.
The coating layer can be formed by any of convention~l methods of film formation. For example, the coating layer is formed in the form of a l~min~te film by melt extrusion using extrusion dies for forming the respective layers.
Each layer of the coating layer may contain additives such as an antio~id~nt, a W light absoll el, a colorant, and so on.
Young's Modulus of Coating Layer A Young's modulus of the whole coating layer in the first or second invention is preferably at least 350 kg/mm2, more preferably from 150 to 250 kg/mm2, in terms of a total value of those in a machine direction (MD) and a transverse direction (TD). When this Young's modulus is too large, the reeiet~n~e to edge chipping may decrease.
Each layer of the coating layer is preferably formed from an unstretched film. Each layer made of the unstretched film can improve rÇciet~nce to heat resistant dimensional stability. The ul,~ Lched film is produced so that a ratio of the Young's modulus in the m~hine direction (MD) to that in the transverse direction (lL~) of the whole coating layer is in the range between 0.8 and 1.25,more preferably between 0.9 and 1.1.

Print Layer According to the present invention, the coating layer can be formed on the surface layer with good adhesion. The print layer can be formed on the surface layer by applying a printing ink which co"""ises a colorant such as a pigment or a dye, and at least one resin selected from thermoplastic resins, thermosetting resins and radiation curable resins, by a coating process such as gravure coating or a printing process such as screen printing. As the thermoplastic resin, an acrylic W096/35969 PCTrUS96/OS629 polymer is p~ led, since it will further improve the adhesion of the print layer to the surface layer comprising the methyl meth~r~rylate base polymer.
The print layer can be formed on the reflective sheet during the production step of the reflective sheet or after adhering the reflective sheet on the article.
When the print layer is formed on the reflective sheet in the production step of the latter, the production process of the reflective sheet comprises either one of the following steps:
(i) 1~...;.~,.1;.~ the ~e~ lenective layer and the coating layer, and Lllele~lleforming the print layer on the surface of the surface layer, or (ii) forming the print layer on the surface of the surface layer to provide the coating layer having the print layer thereon, and l~ g the coating layer having the print layer thereon and the I c;Llolc~nective layer.
To form the print layer by the step (ii), a reflective sheet should include a coating layer having good impact r~sict~n~e as the reflective sheet of the present invention. For example, if the print layer is formed on a conventional coating layer made of a single layer film of the methyl methacrylate base polymer, which will be used in a conventional reflective sheet, minute cracks are generated on the coating layer in the printing step or a subsequent drying step of the print layer, and finally the coating layer is torn and broken. That is, in the production process of the conventional reflective sheet, the above step (ii) cannot be employed.
When the back layer of the reflective sheet of the present invention comprises the methyl meth~-rylate base polymer and the vinylidene fluoride base polymer in the above weight ratio, a print layer can be formed on the surface of the back layer on which the lellulenective layer is l~min~terl, namely, a l~min~tion side, with good ~-1hP~ion To form the print layer on the l~min~tion side of the back layer, the production process of the reflective sheet of the present invention inr~.ludes a step for forming the print layer on the l~min~tion side of the back layer to provide the coating layer having the print layer formed thereon like the above step (ii), and a step fûr l5'-~ AI;--~ the coating layer carrying the print layer thereon onto the ;nective layer.

When such back layer is used, the print layers can be provided on both the outer surface of the surface layer and the outer surface of the back layer, that is, both surfaces of the coating layer.
A plilllillg ink which is used in the formation of the print layer on the ~, 5 1~ n side of the back layer co~ ises preferably an acrylic polymer for the same reason as above.
The print layer can be formed on the l~min~tion side of the back layer by the same method as used in the formation of the print layer on the surface layer.

Article Having Retroreflectiveness In one of the plerelled applications of the reflective sheet of the present invention, the reflective sheet is bonded to a body of an article which should have the rt;lrol ~nectiveness, with bonding means.
In such case, the reflective sheet is processed by cutting or pl~n~.hing out in a desired size and shape before or after it is bonded to the article body with thebonding means.
With the conventional reflective sheet, minute cracks which are hardly visible are geneldl~d on the edges of the coating layer after proc~c~in~, and lL~.~;rore, the reei~t~nre to edge chipping is not good. Since the reflective sheet has the improved resistance to edge chipping as explained above, the present invention can provide the article having the good rellolenectiveness sufficient for practical use.
As the bonding means, any one that is used in the conventional reflective sheet, such as a double sided adhesive tape, a pressure sensitive adhesive, a heat sensitive adhesive, and so on, may be used.
When the article is used outdoors such as a plate of a traffic sign, a plate of a guidepost and so on, a pressure sensitive or heat sensitive adhesive comprising an acrylic polymer is preferably used, since the acrylic polymer can impart good weatherability, suitable tack for bonding the reflective sheet to the article body and an adhesion strength which lasts for relatively long time to the pressure sensitive or heat sensitive adhesive.

W 096/35969 PCTrUS96105629 As the acrylic polymer, a copolymer comprising an alkyl acrylate (e.g.
isooctyl acrylate, butyl acrylate, isobornyl acrylate, etc.) and an acid monomer (e.g.
acrylic acid, etc.) is plcrcllcd. The acrylic polymer may further comprise a base l-,.anû...er such as N,N-.li---t;ll-ylacrylamide, N,N-diethylacrylamide, N-acrylmorpholine, N-acrylpiperidine, and so on. It is plere.. ed for the adhesive to contain a mixture of the acrylic polymer and a phenol resin, so as to increase the adhesion strength onto the article body.

Others In the reflective sheet of the present invention, it is possible to bcro-ehand provide the bonding means in the form of an adhesive layer on the other surface opposite the above one of the major surfaces of the rcL,o,enective layer in the production step of the reflective sheet.
To adjust the :iL,ellgLIl of the reflective sheet as a whole, or to prevent the migration of a pl~$tiri7~r from an article to the rt;~,ulcflective layer when the reflective sheet is adhered to an article of a plastic co~ g a fairly large amount of a plasticizer, a plastic film can be interposed between the adhesive layer and the rcL, o, enective layer.
The details of the production method of the ~ -or~nective sheet will be explained in the examples described later.
According to the present invention, the 1 elrol ~nective sheet has good adhesion of the coating layer to the ~c~o-t;nective layer and the print layer so that the sheet has good practical durability and excellent rçsi~t~nce to edge chipping, and also it is excellent in impact resistance and weaLl-e.~bility.
Examples The present invention will be illustrated by the following examples, which will not limit the scope of the present invention in any way.

W 096/35969 PCTrUS96/05629 Production of Retroreflective Sheet A rellolenective sheet produced in each of Examples and Colllpal~ e Example was an encapsulated lens rt;LI ul ~;nective sheet.
Production steps of the encapsulated lens ,~I,u,t:nective sheet will be (1) On a carrier web having a polyethylene layer of 25 ~m in thirl~nP~
plural ~ arelll microspheres as the lens means were partly embedded det~çh~bly in the polyethylene layer (to a depth co~ .olldillg to about 40 % of a rli~mP,tçr of the microsphere) to form a l-~ls~ale--l microsphere layer which was subst~nt~ y a single layer ofthe microspheres.
(2) On a surface of the exposed part of each microsphere, a reflector comprising an ~ mimlm vapor deposition film of about 0.1 tlm in thickness was formed. In this case, a position of focus of the microsphere was subs~ y on an interface between the microsphere and the ~ mimlm film.

(3) On the reflectors, a bonding layer of about 60 ,um in thickness and a rPle~einF~ film were l~min~ted in this order. Thereafter, the carrier web was removed to form the microsphere layer on one of the major surfaces of the bonding layer where a part of each microsphere was çmbe~ded in the bonding layer while asurface of each microsphere which was not covered by the reflector was exposed.

(4) On the surfaces of the microspheres which were not covered by the reflectors, a film as a coating layer was placed with leaving a predetelll,lned gap between the microsphere layer and the film. Then, on the rPie~ing film, an embossing heater having a nclîollll emboss pattern of thin lines was pressed with heating to emboss the bonding layer through the releasing film, whereby netform linking parts having a narrow width, which bonded the coating layer partly to the bonding layer, were formed. At this stage, the colllbillalion of the linking parts and the coating layer formed plural spaces which encapsulated the Ll ~nsparelll microspheres.

(5) After curing the bonding layer, the rele~cin~ film was removed to expose the other major surface opposite the above one of the major surfaces of the boding layer. On the other major surface, an adhesive layer having a rPlç~in~ liner WO 96/35969 PCT~US96/05629 was lA~ IAIed to obtain a rellul~;nective sheet. The adhesive layer was provided as a bonding means for adhering the rc;L,ul~;nective sheet to an article body.
The above described method is based on the method disclosed in JP-B-61-13561.
Materials of the Retroreflective Sheet Tl an~Jal e"l microspheres:
Glass beads having a refractive index of about 1.9 and an average ~1;A~ ;;I
of 50 to 80 llm.
Bonding layer:
The bonding layer was formed by coating a radiation curable paint, which was p, epal ed by mixing an ethyl acrylate/methyl methacrylate/isooctyl acrylatecopolymer (137 parts by weight), polyethylene glycol (200) diacrylate (20 parts by weight), rutile titAnil~m dioxide (white pipmf~nt) (18 parts by weight), and stearic acid (2 parts by weight) in xylene, on the reflectors in the step (3). In the step (5), the bonding layer was cured by irradiation of cle~,l,on beam.
Adhesive layer:
The adhesive layer contained an isooctyl acrylate/acrylic acid copolymer (a weight ratio of the monomers = 94:6).
Coating layer:
The coating layer will be explained in each example.

Example 1 A rel, Ol t;nective sheet of this ~Aam~le was produced by the above described production method using, as the coating layer, a three layer film having a surface layer, an interme-liAte layer and a back layer in this order, and a total thickness of 50 m.
In this example, the surface layer c~ ntAin~d 90 wt. % of polymethyl mPthAcrylate and 10 wt. % of polyvinylidene fluoride and had a thi~knP,ss of about 10 ~lm. The interm~iAte 1ayer co"lai"ed 10 wt. % of polymethyl mPthArrylate and 90 wt. % of polyvinylidene fluoride and had a thickness of about 30 ~lm. The back W 096/3S969 PCTrUS96/05629 layer cont~ined 90 wt. % of polymethyl meth~crylate and 10 wt. % of polyvinylidene fluoride and had a thickness of about 10 ,um.
The above film was produced by extrusion mol 1in~ using an extruder accordh.g to the method tlie~losed in JP-A-6-80794.
O 5 As polymethyl meth~r.rylate, a poly-netl.~l meth~crylate resin HBS 001 (a trade name of Mi~subisl i Rayon Co., Ltd.) was used. As polyvinylidene fluoride, a polyvinylidene fluoride resin having an average spherulite rli~met~r of about 1.5 ~lm was used.
Physical properties of the film used as the coating layer in this cA~---ple are shown in Table 1. The tensile strength, elongation at break and Young's modulus of the coating layer were measured according to JIS K6732, and the whole light tr~nemieeion and cloudiness of the coating layer were measured accolding to JIS
K6714.
The results of evaluation of the ~L~ult;nective sheet produced in this example are shown in Table 2. The evaluation methods are exrl~ine~l below. In the subsequent examples, the evaluation was carried out by the same methods.

Impact Rçeiet~nce To a surface of an ~Illmimlm plate having sizes of 150 mm x 70 mm x 1 mm, the retroreflective sheet having an area slightly larger than that of the ~ min~lm plate was adhered using a hand squeeze roll applicator, and a ...alginal edge part was trimmed to remove a ...a.~inal part of the sheet to obtain a sample for evaluation.
At a temperature of 20~C, using a Gardner impact tester, a weight of the tester was fallen on the reflective sheet sample under the condition of 40 inch.pound, and a degree of damage of the sample was observed. When the peeling was found between the coating layer and the bonding layer, or when many cracks were generated in the parts of the coating layer over the spaces enc~rs--l~ting the pa.~ microspheres while no peeling offwas found between the coating layer and the bonding layer, the result was ranked "NG" (No good). When peeling or crack was not generated, the result was ranked "OK".

W 096/35969 PCTrUS96/05629 Heat Re~ict~nt Dimensional Stability A reflective sheet sample was produced in the same manner as in the impact le~ ce test but sizes of an Alllmimlm plate were l~h~n~ec~ to 152 mm x 152 mm x 1 6mm The sheet sample was kept stAnding in an oven ,.,~ d at 120~C for 30 ..;..~les and :,~an~ eously cooled in a room tt;~ ,c; ~ re atmosphere. Then, an area in which the reflective sheet shrank was ..,easured, and a pe-~t;--l~ge of that area to an ordinal area (152 mm x 152 mm) was c~lc~llAted and used as a criterion value ofthe heat resistant dimensional stability (unit: %) Weatherability A reflective sheet sample was produced in the same manner as in the impact reci~tAn~e test The sample was set in a Weather-O-meter and subjected to an accelerated weathering test for 2200 hours under the conditions of JIS Z9105, Item 8 4 "Sunshine Carbon Type Accelerated Weathering Test" Then, the following prope. Lies were eVal~lAte~l (a) T ~ e retention rate (unit: %) A pelcenLage of a reflection 11 ~ A~re on the reflective sheet after the accelerated ~eall.e.i--g test to the reflection l~minAnce on the reflective sheet measured before the accelerated weathering test was calculated The reflection IllminAnce was measured using a reflectometer "Model 920" (mAmlfActllred by Advanced Retro Technology) (b) Gloss retention rate (unit: %) A percentage of a gloss on the reflective sheet after the accelerated weathering test to the gloss on the reflective sheet measured before the accelerated weathering test was c~ te~l: The gloss was measured using a glossmeter "GMX-202" (mAmlfActllred by Murakami Shikisai Kenkyusho Co., Ltd ) (c) Color di~. ence (~E) Before and after the accelerated weathering test, the color di~erence of the reflective sheet was measured using a color difference meter "~:-80".. A. r~ctllred W 096/35969 PCT~US96/05629 by Nippon Denshoku Kogyo Co., Ltd.). A D65 light source was used, an angle of observation was 10 degrees, and the color difference was determined accordin~ tothe method defined in JIS Z8730.

G S Adhesion of Print Layer A reflective sheet sample was produced in the same manner as in the impact ee;e~ r,e test. On the sheet sample, a print layer was screen printed using a traffic sign printing ink (co..lA;..;.~g an acrylic polymer), and subjected to the following peel test:
An adhesive tape #610 (m~nllf~ct~lred by 3M) was firmly adhered to the surface of the print layer with a squeegee, and quickly peeled off. When the print layer was peeled off from the surface of the coating layer, the adhesion was ranked "NG". When the print layer was not peeled off, the adhesion was ranked "OK".
Adhesion between the coating layer and the ~e~l,or~nective layer (bonding layer).
lS As a sample for evaluation, the coating layer used in the retroreflective sheet was used. On the l~min~tion side of the back layer of the coating layer, a paint for the bonding layer was coated to a thickness of 10 ~lm, dried and cured to form afilm of the bonding material. With this film, the same peel test as in the evaluation test of the adhesion of print layer was done. When the film was peeled off, the adhesion was ranked "NG". When the film was not peeled off, the adhesion was ranked "OK".

~esiet~nce to Edge Chippin~
A reflective sheet sample was produced in the same manner as in the impact reeiet~nce test, except that the adhering position of the sheet was selected so that the largest number of the spaces encapsnl~tin~ the l,~ns~ale"l microspheres wereplaced at the edge of the reflective sheet. The sample surface on the edge was rubbed with a finger five times in a direction from the edge to the center of the sheet. When the coating layer was chipped or peeled off to expose the l~ l elll microspheres, the reeiet~nce was ranked "NG". When no ~ a~ microsphere was exposed, the resiet~nre was ranked "OK".

W O 96/35969 PCTrUS96105629 Example 2 In the same manner as in Fx~mp~e 1 except that a two layer film which consisted of a surface layer and a back layer which had the following compositions and had a total th; ~nPs~ of S0 ~lm was used, a ~el~u~t:nective sheet was produced.
The surface 1ayer co,ll~ned 75 wt. % of polymethyl meth~rrylate and 25 wt.
% of polyvinylidene fluoride and had a thir~ness ûf about 5 ,um, and the back layer co"~ ,ed 70 wt. % of polymethyl mçth~crylate and 30 wt. % of polyvinylidene fluoride and had a thickness of about 45 ~m.
The physical properties of the film used in this example are shown in Table 1, and the results of evaluation of the .t:l-o.t;nective sheet produced in this example are shown in Table 2.

Example 3 lS In the same manner as in Example 2 except that a two layer film whichconsisted of a surface layer and a back layer which had the following compositions was used, a ,el-olt:nective sheet was produced.
The surface layer contained 65 wt. % of polymethyl meth~crylate and 35 wt.
% of polyvinylidene fluoride, and the back layer contained 60 wt. % of polymethyl meth~c.rylate and 40 wt. % of polyvinylidene fluoride.
The physical plupel~ies of the film used in this example are shown in Table 1, and the results of evaluation of the, ~;L. Ol t:nective sheet produced in this example are shown in Table 2.

Cu~ eExample 1 In the same manner as in Example 1 except that a biaxially stretched single layer film of polymethyl meth~:rylate having a th~c~nes~ of ~0 ~lm was used, a rc;LIo~;nective sheet was produced.
The results of evaluation of the ,ello.~nective sheet produced in this example are shûwn in Table 2.

.

W O 96/35969 PCTrUS96/05629 Col,lpal~Li~e Example 2 In the same manner as in Example 1 except that a biaxially stretched impact resistant single layer film of an acrylic resin having a thir~ness of 50 ~lm was used, a reL,orenective sheet was produced.
. 5 The used acrylic resin was a blend resin of polymethyl meth~crylate and an acrylic polyphase interpolymer, which is ~i~closed in ~ A-61-255846.
The results of evaluation of the rellolenective sheet produced in this c ~Il?lc are shown in Table 2.

Colllpa-~Li~e Example 3 In the same manner as in Colll?al~lhle Example 2 except that a film as the coating layer was an unstretched film, a lelrorenective sheet was produced.
The results of evaluation of the leLI~lenective sheet produced in this example are shown in Table 2.
Col..?a.aLi~e Example 4 In the same manner as in Example 1 except that a three layer film comprising a surface layer, an interme~i~te layer and a back layer which had thefollowing compositions was used as the coating layer film, a It;Llolenective sheet was produced.
The surface layer collL~ined 40 wt. % of polymethyl meth~l~rylate and 60 wt.
% of polyvinylidene fluoride, the interme~i~te layer conLail~ed 50 wt. % of polymethyl methacrylate and 50 wt. % of polyvinylidene fluoride, and the back layer conLained 50 wt. % of polymethyl m.oth~crylate and 50 wt. % of polyvinylidene fluoride.
The physical prop~il Lies of the film used in this example are shown in Table 1, and the results of evaluation of the I t:LI ort:nective sheet produced in this example are shown in Table 2.

.

W 096/35969 PCT~US96/05629 Example 4 In the same manner as in Example 1 except that polyvinylidene fluoride having an average spherulite r1i~m~ter of about 1.7 llm was used in the three layer film, a r ell u- enective sheet was produced.
The physical prope.lies of the film used in this ~Y~mple are shown in Table 1, and the results of evaluation of the r~cLlorenective sheet produced in this c.~---ple are shown in Table 2.

E~alll?le 5 In the same manner as in Example l except that a three layer film comprising a surface layer, an interme~ te layer and a back layer which had the following compositions was used as the coating layer film, a r~l.urt;nective sheet was produced.
The surface layer contained 60 wt. % of polymethyl meth~crylate and 40 wt.
% of polyvinylidene fluoride, the intermefli~te layer contained 40 wt. % of polymethyl meth~crylate and 60 wt. % of polyvinylidene fluoride, and the back layer crnt~ined 60 wt. % of polymethyl meth~r.rylate and 40 wt. % of polyvinylidene fluoride.
The physical properties of the film used in this example are shown in Table 1, and the results of evaluation of the retroreflective sheet produced in this example are shown in Table 2.

Example 6 In the same manner as in Ex~ le 1 except that a three layer film comprising a surface layer, an inte~ e~ e layer and a back layer which had the following compositions was used as the coating layer film, a rc;L.u.~flective sheet was produced.
The surface layer contained 75 wt. % of polymethyl meth~crylate and 25 wt.
% of polyvinylidene fluoride, the intermedi~te layer contained 25 wt. % of polymethyl m.oth~.rylate and 75 wt. % of polyvinylidene fluoride, and the back layer W 096/3S969 PCT~US96/05629 co"lailled 75 wt. % of polymethyl meth~rrylate and 25 wt. % of polyvinylidene fluoride.
The physical prop~l lies of the film used in this example are shown in Table 1, and the results of evaluation ofthe ,tl,ol~nective sheet produced in this c,.~nplc ~, 5 are shown in Table 2.

Example 7 In the same manner as in F.Y~mple 2 except that a two layer film CC""p~iSi~lg a surface layer and a back layer which had the following compositions was used as the coating layer film, a lell c" t;nective sheet was produced.
The surface layer conL~ ed 90 wt. % of polymethyl methacrylate and 10 wt.
% of polyvinylidene fluoride, and the back layer contained 85 wt. % of polymethyl meth~rylate and 15 wt. % of polyvinylidene fluoride.
The physical properties of the film used in this example are shown in Table 1, and the results of evaluation ofthe lt;llolenective sheet produced in this example are shown in Table 2.

Table 1 Ex.TensileFl~ng~ti~n at Young~s ModulusT~ ic~ ClQll~lin~:
No.Streng~Break (~/0)~cg/rnm2)to all Light(~/0) 2) (5) M D TD M D TDC M D TD
2.9 2.5 135 109 109 108 92.2 3.3 2 3.3 2.5 137 80 120 114 93.1 1.7 3 3.3 2.8 176 148 107 107 93.2 1.1 4 2.8 2.4 136 101 105 106 89.7 10.7 3.3 2.9 13~ 108 108 107 92.1 2.7 6 3.4 2.9 143 130 101 99 92.0 2.8 7 3.7 3.5 120 100 125 121 92.7 1.9 C. 1 3.2 3.0 151 129 102 100 91.1 2.6 -o o o o ~ z z z o o o o ~ o o o ~ ~o o o o o o o o o o Z o o o ¢ _, ~ C ~ ~ o ~ X ~ ~. ~ ~
V ~ ~ o o' o o o o o o o o o E~
o o~ o ct~ O O O O O oO o~
~r ~ _ o o _ _ 3 8~

o o o o z z z z o o o ~ z c~ ~ v v

Claims

CLAIMS:

1. A retroreflective article that comprises:
(a) a retroreflective layer having first and second major surfaces, and (b) a cover layer juxtaposed against the first major surface, characterized in that:
the cover layer comprises a surface layer, an optional intermediate layer, and a back layer, with the provisos that: (i) when the intermediate layer is present in the cover layer the intermediate layer contains a vinylidene fluoride base polymer as a primary component, and the surface layer and back layer each comprise a methyl methacrylate base polymer as a primary component; and (ii) when the intermediatelayer is absent from the cover layer, the surface layer comprises a methyl methacrylate base polymer (A) and a vinylidene fluoride base polymer (F) in a weight ratio A:F of 55:45 to 95:5, and the back layer comprises a methyl methacrylate base polymer and a vinylidene fluoride base polymer with the vinylidene fluoride base polymer being the primary component.

2. The retroreflective article of claim 1, wherein said back layer comprises a methyl methacrylate base polymer (A) and a vinylidene fluoride base polymer (F) in a weight ratio A:F of from 55:45 to 95:5.

3. The retroreflective article of claim 2, wherein a content of the vinylidene fluoride base polymer in the back layer is larger than that in the surface layer.

4. The retroreflective article of claim 2 having a print layer on a side of the back layer that faces the retroreflective layer.

5. The retroreflective article of claim 1, containing the intermediate layer, which intermediate layer comprises a methyl methacrylate base polymer (A) and a vinylidene fluoride base polymer (F) in a weight ratio A:F of from 5:95 to 45:55.

6. The retroreflective article of claim 1, wherein the surface layer comprises a methyl methacrylate base polymer (A) and a vinylidene fluoride base polymer (F) in a weight ratio A:F of from 55:45 to 95:5.

7. The retroreflective article of claim 1, wherein said back layer comprises a methyl methacrylate base polymer (A) and a vinylidene fluoride base polymer (F) in a weight ratio (A:F) of from 55:45 to 95:5.

8. The retroreflective article of claim 7 having a print layer on a side of the back layer facing the retroreflective layer.

9. The retroreflective article of claim 1, wherein the coating layer transmits at least 90% of light incident thereon.

10. The retroreflective article of claim 1, wherein the retroreflective layer comprises:
a layer of transparent microspheres;
a support member in which are partially embedded;
a bonding layer having plural linking parts that are bonded to the coating layer so that spaces for encapsulating said transparent microspheres are formed between the coating layer and the bonding layer; and reflectors that are located beneath the layer of transparent microspheres.

11. The retroreflective article of claim 10, wherein the bonding layer comprises an acrylic polymer.

12. The retroreflective article of claim 1 secured to a second article.