Abstract:
A fluorescent yellow article comprising polyolefin copolymer, perylene imide dye N,N&#39;-bis(2,6-di-isopropylphenyl)-3,4:9,10-perylenebis(dicarboximide), and at least one yellow-green dye selected from the group consisting essentially of Lumogen F Yellow 083, CI Solvent Yellow 98, CI Solvent Yellow 160:1, Oraset Yellow 8GF, CI Solvent Green 4, CI Solvent Green 5, CI Pigment Yellow 101 and CI Solvent Yellow 131 wherein the resultant article has chromaticity coordinates (x,y) within the area defined by (0.425,0.480), (0.465,0.535), (0.557,0.440), and (0.500,0.410) in terms of the CIE 1931 Standard Colorimetric System and measured using 0/45 geometry and evaluated with CIE Standard Illuminant D65.

Description:
FIELD OF THE INVENTION 
     The invention relates to fluorescent coloring. Specifically the invention relates to providing fluorescent yellow articles. 
     BACKGROUND OF THE INVENTION 
     It is commonly known that fluorescent colors provide increased visibility for visual signaling under most lighting conditions, but particularly under low natural lighting conditions. These low natural lighting conditions occur at dusk and also at sunrise and present a challenge for traffic sign manufacturers. If increased visibility of an article is desired, the article is often colored with fluorescent colorants. Fluorescent colors allow enhanced visibility because the visual contrast that the fluorescent colors create with the environment make the materials more conspicuous than ordinary nonfluorescent articles. Fluorescent colored traffic signs are effective at increasing the visibility of the signs which increases motorist safety. 
     Even though fluorescent signs increase motorist safety, their use for yellow signs has been limited due to the difficulty to obtain a true fluorescent yellow. To date, fluorescent colorants are available in only a limited range of hues. For example, fluorescent colorants are commercially available and include fluorescent red, fluorescent orange and fluorescent yellow-green. However, a true fluorescent yellow which meets the chromaticity requirements of Commission Internationale de l&#39;eclairage (CIE) and ASTM is not readily available. As is known in the art the CIE provides international recommendations for surface colors for visual signaling. 
     Formulating colors using ordinary or conventional colorants is well known. Ordinary colors do not emit light. Therefore, when formulating colors with ordinary colorants, the important parameters to consider are the light absorptive and light reflective properties of the colorants. On the other hand, fluorescent colors do emit light. Therefore, when formulating with fluorescent colorants the important parameters to consider are the light absorptive, light reflective and light emissive properties of the fluorescent colorants. Due to this distinction between ordinary and fluorescent colors, an added consideration is necessary when formulating colors with fluorescent dyes. 
     The art of formulating colors from ordinary colorants is well-developed. For example, it is known that a mixture of a blue colorant with a red colorant will give a purple color. However, the art of formulating colors from fluorescent colorants is not well-defined. U.S. Pat. No. 4,443,226 issued to Rohser describes combining thioindigo and/or derivatives of the red and pink series of thioindigo with specific yellow disperse dyestuffs to obtain a shade of fluorescent orange-red as required to meet color point, luminance and fastness to light. 
     The need exists for yellow fluorescent articles such as those useful for visual signaling, for example, traffic signing. The art does not currently possess such yellow fluorescent articles nor an obvious way to achieve them. 
     SUMMARY OF THE INVENTION 
     The invention provides fluorescent articles which have a yellow color with chromaticity coordinates within the CIE and ASTM requirements. Each article is comprised of a polymeric matrix and a blend of at least two different dyes selected specifically for the polymeric matrix which is used in the article. Also provided are fluorescent yellow retroreflective sheeting and methods of manufacturing such sheeting. 
     A fluorescent yellow article is provided which comprises a polyolefin copolymer, a perylene imide dye, N,N&#39;-bis(2,6-di-isopropylphenyl)-3,4:9,10-perylenebis(dicarboximide), and a yellow-green dye selected from the group of Lumogen F Yellow 083, CI Solvent Yellow 98, CI Solvent Yellow 160:1, Oraset Yellow 8GF, CI Solvent Green 4, CI Solvent Green 5, CI Pigment Yellow 101 and CI Solvent Yellow 131. The resultant article has chromaticity coordinates (x,y) within the area defined by (0.425,0.480), (0.465,0.535), (0.557,0.440), and (0.500,0.410) in terms of the CIE 1931 Standard Colorimetric System and measured using 0/45 geometry and evaluated with CIE Standard Illuminant D65. 
     A fluorescent yellow article is provided which comprises polycarbonate, at least one perlyene imide dye selected from the group of N,N&#39;-bis(2,6-di- isopropylphenyl)3,4:9,10-perylenebis(dicarboximide), N,N&#39;-bis(octadecyl)-3,4:9,10-perylenebis(dicarboximide), and N,N&#39;-bis(phenethyl)-3,4:9,10-perylenebis(dicarboximide) and at least one yellow-green dye selected from the group of Lumogen F Yellow 083, CI Solvent Yellow 98, CI Solvent Yellow 160:1, Onset Yellow 8GF, CI Solvent Green 4, CI Solvent Green 5, CI Pigment Yellow 101, Golden Yellow D-304 and CI Solvent Yellow 131. The resulting article has chromaticity coordinates (x,y) within the area defined by (0.425,0.480), (0.465,0.535), (0.557,0.440), and (0.500,0.410) in terms of the CIE 1931 Standard Colorimetric System and measured using 0/45 geometry and evaluated with CIE Standard Illuminant D65. 
     A fluorescent yellow article comprising polyester, at least one perlyene imide dye selected from the group of N,N&#39;-bis(2,6-di-isopropylphenyl)-3,4:9,10-perylenebis(dicarboximide) and N,N&#39;-bis(octadecyl)-3,4:9,10-perylenebis(dicarboximide) and at least one yellow-green dye selected from the group of Lumogen F Yellow 083, CI Solvent Yellow 98, CI Solvent Yellow 160:1, Oraset Yellow 8GF, CI Solvent Green 4, CI Solvent Green 5, CI Pigment Yellow 101, Golden Yellow D-304, and CI Solvent Yellow 131 wherein the resulting article has chromaticity coordinates (x,y) within the area defined by (0.425,0.480), (0.465,0.535), (0.557,0.440), and (0.500,0.410) in terms of the CIE 1931 Standard Colorimetric System and measured using 0/45 geometry and evaluated with CIE Standard Illuminant D65. 
     A fluorescent yellow article which comprises a polyester/polycarbonate alloy, a perylene imide dye selected from the group of N,N&#39;-bis(2,6-di-isopropylphenyl)-3,4:9,10-perylenebis(dicarboximide) and N,N&#39;-bis(octadecyl)-3,4:9,10-perylenebis(dicarboximide) and at least one yellow-green dye selected from the group consisting Lumogen F Yellow 083, CI Solvent Yellow 98, CI Solvent Yellow 160:1, Oraset Yellow 8GF, CI Solvent Green 4, CI Solvent Green 5, CI Pigment Yellow 101, Golden Yellow D-304 and CI Solvent Yellow 131 wherein the resultant article has chromaticity coordinates (x,y) within the area defined by (0.425,0.480), (0.465,0.535), (0.557,0.440), and (0.500,0.410) in terms of the CIE 1931 Standard Colorimetric System and measured using 0/45 geometry and evaluated with CIE Standard Illuminant D65. 
     A fluorescent yellow article comprising polymethylmethacrylate, a perlyene imide dye, N,N&#39;-bis(2,6-di-isopropylphenyl)-3,4:9,10-perylenebis(dicarboximide), and at least one yellow-green dye selected from the group of Lumogen F Yellow 083, CI Solvent Yellow 98, CI Solvent Yellow 160:1, Oraset Yellow 8GF, CI Solvent Green 4, CI Solvent Green 5, CI Pigment Yellow 101, Golden Yellow D-304, and CI Solvent Yellow 131 wherein the resultant article has chromaticity coordinates (x,y) within the area defined by (0.425,0.480), (0.465,0.535), (0.557,0.440), and (0.500,0.410) in terms of the CIE 1931 Standard Colorimetric System and measured using 0/45 geometry and evaluated with CIE Standard Illuminant D65. 
     A fluorescent yellow article which comprises polymethylmethacrylate/polyvinylidine fluoride alloys, a perlyene imide dye, N,N&#39;-bis(2,6-di-isopropylphenyl)-3,4:9,10-perylenebis(dicarboximide), and at least one yellow-green dye selected from the group of Lumogen F Yellow 083, CI Solvent Yellow 98, CI Solvent Yellow 160:1, Oraset Yellow 8GF, CI Solvent Green 4, CI Solvent Green 5, CI Pigment Yellow 101, Golden Yellow D-304, and CI Solvent Yellow 131 wherein the resultant article has chromaticity coordinates (x,y) within the area defined by (0.425,0.480), (0.465,0.535), (0.557,0.440), and (0.500,0.410) in terms of the CIE 1931 Standard Colorimetric System and measured using 0/45 geometry and evaluated with CIE Standard Illuminant D65. 
     A fluorescent yellow article comprising aromatic and aliphatic polyurethanes derived from monomers selected from the group of diisocyanates, polydiols, and chain extenders such as butanediol and hexanediol, a perlyene imide dye, N,N&#39;-bis(2,6-di-isopropylphenyl)-3,4:9,10-perylenebis(dicarboximide), and at least one yellow-green dye selected from the group of Lumogen F Yellow 083, CI Solvent Yellow 98, CI Solvent Yellow 160:1, Oraset Yellow 8GF, CI Solvent Green 4, CI Solvent Green 5, CI Pigment Yellow 101, Golden Yellow D-304 and CI Solvent Yellow 131 wherein the resultant article has chromaticity coordinates (x,y) within the area defined by (0.425,0.480), (0.465,0.535), (0.557,0.440), and (0.500,0.410) in terms of the CIE 1931 Standard Colorimetric System and measured using 0/45 geometry and evaluated with CIE Standard Illuminant D65. 
     A fluorescent yellow article comprising polyvinylchloride, a perlyene imide dye, N,N&#39;-bis(2,6-di-isopropylphenyl)-3,4:9,10-perylenebis(dicarboximide), and at least one yellow-green dye selected from the group of Lumogen F Yellow 083, CI Solvent Yellow 98, CI Solvent Yellow 160:1, Oraset Yellow 8GF, CI Solvent Green 4, CI Solvent Green 5, CI Pigment Yellow 101, Golden Yellow D-304 and CI Solvent Yellow 131 wherein the resultant article has chromaticity coordinates (x,y) within the area defined by (0.425,0.480), (0.465,0.535), (0.557,0.440), and (0.500,0.410) in terms of the CIE 1931 Standard Colorimetric System and measured using 0/45 geometry and evaluated with CIE Standard Illuminant D65. 
     A method of manufacturing a fluorescent yellow article comprising the steps of (a) combining polymethylmethacrylate, a perlyene imide dye N,N&#39;-bis(2,6-di-isopropylphenyl)-3,4:9,10-perylenebis(dicarboximide) and at least one yellow-green dye selected from the group consisting essentially of Lumogen F Yellow 083, CI Solvent Yellow 98, CI Solvent Yellow 160:1, Oraset Yellow 8GF, CI Solvent Green 4, CI Solvent Green 5, CI Pigment Yellow 101, Golden Yellow D-304, and CI Solvent Yellow 131 wherein the resultant article has chromaticity coordinates (x,y) within the area defined by (0.425,0.480), (0.465,0.535), (0.557,0.440), and (0.500,0.410) in terms of the CIE 1931 Standard Colorimetric System and measured using 0/45 geometry and evaluated with CIE Standard Illuminant D65; and (b) extruding said combination to provide a film. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is further explained with reference to the drawings, wherein: 
     FIG. 1 is a cross-sectional illustration of a portion of one retroreflective embodiment of the invention; 
     FIG. 2 is a cross-sectional illustration of a portion of another retroreflective embodiment of the invention; 
     FIG. 3 is a cross-sectional illustration of another retroreflective embodiment of the invention; and 
     FIG. 4 is a CIE 1931 Chromaticity diagram defining the area of color space defined herein as yellow. 
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Definitions 
     As referred to herein, the term &#34;colorant&#34; shall mean pigment or dyes or other substances used to impart hue and chroma and value to an article. 
     As referred to herein, the term &#34;conventional colorant&#34; or &#34;ordinary colorant&#34; are used interchangeably herein and shall mean colorants which do not exhibit fluorescent properties. 
     As referred to herein, the term &#34;dye&#34; shall mean substances which impart color to a substrate by selective absorption of light. Dyes are soluble and/or go through an application process which, at least temporarily, destroys any crystal structure of the color substances. Dyes are retained in the substrate by absorption, solution, and mechanical retention, or by ionic or covalent chemical bonds. 
     As referred to herein the term &#34;fluorescent dye&#34; shall mean a dye which absorbs light at a first wavelength and emits at second wavelength which is longer than the first wavelength. 
     As referred to herein the term &#34;yellow&#34; shall mean the color which is within the area defined by the four CIE chromaticity coordinates plotted and shown in FIG. 4: 
     
         ______________________________________   x    y______________________________________   .500 .410   .425 .490   .465 .535   .557 .440______________________________________ 
    
     Preferably the area is defined by chromacity coordinates (x,y): (0.425,0.48), (0.465,0.535), (0.557,0.44) and (0.5,0.41); more preferably (0.425,0.48), (0.465,0.535), (0.532,0.465) and (0.48,0.43); and most preferably (0.44,0.5), (0.465,0.535), (0.532,0.465) and (0.5,0.443). The most preferred range defines high saturations of color. 
     The invention is obtained by combining a yellow-green fluorescent dye with a perylene imide dye in a polymeric matrix in which the blend of dyes is soluble. The perylene imide dye used in the invention are orangish in appearance. The combination of dyes has been found to be polymer-specific, therefore, each polymer is discussed individually with the suitable perylene imide dye(s) and the suitable yellow-green fluorescent dye(s) for that polymer. Suitable polymers are polycarbonates, polyurethanes, polyolefins, polyesters, polyvinyls, polyacrylates and blends and copolymers thereof 
     Polyolefin Copolymers 
     The polyolefin copolymers of poly(ethylene-co-acrylic acid) such as Primacor 3440 from Dow Chemical Company of Midland, Mich. and poly(ethylene-co-methacrylic acid) such as Nucrel 699 available from E.I. duPont Nemours of Wilmington, Del. are useful in the present invention with at least one perylene imide and at least one yellow-green dye chosen from the following groups of dyes. A perylene imide dye that is useful in polyolefin copolymers is N,N&#39;-bis(2,6-di-isopropylphenyl)-3,4:9,10-perylenebis(dicarboximide). Any of the yellow-green dyes chosen from the following group may be combined with the perylene imide in polyolefin: Lumogen F Yellow 083 available from BASF of Ludwigshafen, Germany, CI Solvent Yellow 98, CI Solvent Yellow 160:1, Oraset Yellow 8GF available from Ciba-Geigy of Basel, Switzerland, CI Solvent Green 4, CI Solvent Green 5, CI Pigment Yellow 101 and CI Solvent Yellow 131. 
     Polycarbonate 
     Polycarbonate is a matrix which is useful in the invention. Perlyene imide dyes N,N&#39;-bis(2,6-di-isopropylphenyl)-3,4:9,10-perylenebis(dicarboximide), N,N&#39;-bis(octadecyl)-3,4:9,10-perylenebis(dicarboximide), and N,N&#39;-bis(phenethyl)-3,4:9,10-perylenebis(dicarboximide) or combinations thereof are useful in polycarbonate matrices. Any of the mentioned perylene imide dyes may be combined with at least one yellow-green dye selected from the group of Lumogen F Yellow 083 available from BASF of Ludwigshafen, Germany, CI Solvent Yellow 98, CI Solvent Yellow 160:1, Oraset Yellow 8GF available from Ciba-Geigy of Basel, Switzerland, CI Solvent Green 4, CI Solvent Green 5, CI Pigment Yellow 101, Golden Yellow D-304 available from Day-Glo of Cleveland, Ohio, and CI Solvent Yellow 131. 
     Polyesters 
     Polyester is a matrix which is useful in the invention. Perlyene imide dyes N,N&#39;-bis(2,6-di-isopropylphenyl)-3,4:9,10-perylenebis(dicarboximide) and N,N&#39;-bis(octadecyl)-3,4:9,10-perylenebis(dicarboximide) or combinations thereof are useful in polycarbonate matrices. Any of the mentioned perylene imide dyes may be combined with at least one yellow-green dye selected from the group of Lumogen F Yellow 083 available from BASF of Ludwigshafen, Germany, CI Solvent Yellow 98, CI Solvent Yellow 160:1, Oraset Yellow 8GF available from Ciba-Geigy of Basel, Switzerland, CI Solvent Green 4, CI Solvent Green 5, CI Pigment Yellow 101, Golden Yellow D-304 available from Day-Glo of Cleveland, Ohio, and CI Solvent Yellow 131. 
     Polycarbonate/Polyester Blends 
     Polyester/polycarbonate alloys such as DA003 available from Eastman Chemical Company, Kingsport, Tenn. is a matrix which is useful in the invention. Perlyene imide dyes N,N&#39;-bis(2,6-di-isopropylphenyl)-3,4:9,10-perylenebis(dicarboximide) and N,N&#39;-bis(octadecyl)-3,4:9,10-perylenebis(dicarboximide) or combinations thereof are useful in polycarbonate matrices. Any of the mentioned perylene imide dyes may be combined with at least one yellow-green dye selected from the group of Lumogen F Yellow 083 available from BASF of Ludwigshafen, Germany, CI Solvent Yellow 98, CI Solvent Yellow 160:1, Oraset Yellow 8GF available from Ciba-Geigy of Basel, Switzerland, CI Solvent Green 4, CI Solvent Green 5, CI Pigment Yellow 101, Golden Yellow D-304 available from Day-Glo of Cleveland, Ohio, and CI Solvent Yellow 131. 
     Polymethylmethacrylate 
     Polymethylmethacrylate such as CP924 available from ICI Acrylics of St. Louis, Mo. is a matrix which is useful in the invention. Perlyene imide dye N,N&#39;-bis(2,6-di-isopropylphenyl)-3,4:9,10-perylenebis(dicarboximide) is useful in polymethylmethacrylate matrices. This perylene imide dye may be combined with at least one yellow-green dye selected from the group of Lumogen F Yellow 083 available from BASF of Ludwigshafen, Germany, CI Solvent Yellow 98, CI Solvent Yellow 160:1, Oraset Yellow 8GF available from Ciba-Geigy of Basel, Switzerland, CI Solvent Green 4, CI Solvent Green 5, CI Pigment Yellow 101, Golden Yellow D-304 available from Day-Glo of Cleveland, Ohio, and CI Solvent Yellow 131. 
     Polymethylmethacrylate/Polyvinylidine fluoride 
     Polymethylmethacrylate/Polyvinylidine fluoride is a matrix which is useful in the invention. Perlyene imide dye N,N&#39;-bis(2,6-di-isopropylphenyl)-3,4:9,10-perylenebis(dicarboximide) is useful in polymethylmethacrylate/polyvinylidine fluoride matrices. This perylene imide dye may be combined with at least one yellow-green dye selected from the group of Lumogen F Yellow 083 available from BASF of Ludwigshafen, Germany, CI Solvent Yellow 98, CI Solvent Yellow 160:1, Oraset Yellow 8GF available from Ciba-Geigy of Basel, Switzerland, CI Solvent Green 4, CI Solvent Green 5, CI Pigment Yellow 101, Golden Yellow D-304 available from Day-Glo of Cleveland, Ohio, and CI Solvent Yellow 131. 
     Polyurethane 
     Aromatic and aliphatic polyurethanes derived from the following monomers (1)-(3): (1) diisocyanates such as dicyclohexylmethane-4,4&#39;-diisocyanate, isophorone diisocyanate, 1,6-hexamethylene diisocyanate, cyclohexyl diisocyanate, diphenylmethane diisocyanate, and combinations of these diisocyanates, (2) polydiols such as polypentyleneadipate glycol, polytetramethylene ether glycol, polycaprolactonediol, poly-1,2-butylene oxide glycol, and combinations of these polydiols, and (3) chain extenders such as butanediol and hexanediol are useful polymer matrices in the invention. A commercially available urethane polymer includes: PN-03, from Morton International Inc., of Seabrook, N.H. Perlyene imide dye N,N&#39;-bis(2, 6-di-isopropylphenyl)-3,4:9,10-perylenebis(dicarboximide) is useful in polyurethane matrices. This perylene imide dye may be combined with at least one yellow-green dye selected from the group of Lumogen F Yellow 083 available from BASF of Ludwigshafen, Germany, CI Solvent Yellow 98, CI Solvent Yellow 160:1, Onset Yellow 8GF available from Ciba-Geigy of Basel, Switzerland, CI Solvent Green 4, CI Solvent Green 5, CI Pigment Yellow 101, Golden Yellow D-304 available from Day-Glo of Cleveland, Ohio, and CI Solvent Yellow 131. 
     Polyvinylchloride 
     Polyvinylchlorides are matrices which are useful in the invention. Perlyene imide dye N,N&#39;-bis(2,6-di-isopropylphenyi)-3,4:9,10-perylenebis(dicarboximide) is useful in polyurethane matrices. This perylene imide dye may be combined with at least one yellow-green dye selected from the group of Lumogen F Yellow 083 available from BASF of Ludwigshafen, Germany, CI Solvent Yellow 98, CI Solvent Yellow 160:1, Oraset Yellow 8GF available from Ciba-Geigy of Basel, Switzerland, CI Solvent Green 4, CI Solvent Green 5, CI Pigment Yellow 101, Golden Yellow D-304 available from Day-Glo of Cleveland, Ohio, and CI Solvent Yellow 131. 
     Dye Ratios and Loadings 
     The ratio of the yellow-green dye to perylene imide dye may vary over a wide range. In suitable proportions dye blends of the invention will provide a yellow fluorescent color within the chromaticity coordinates for yellow as defined above which encompass both the ASTM and CIE limits for visual signaling yellow. The range of yellow-green dye to perylene imide dye to obtain a fluorescent yellow is in the range from about 100 parts perylene imide dye to 1 part yellow-green dye by weight to about 10 parts perylene imide dye to 100 parts yellow-green dye. One skilled in the art will recognize that the actual ratio chosen will depend upon variables depending upon the intended final use of the invention. This includes the molecular weight and the absorption characteristics (such as molar absorptivity) of the specific dyes employed, and also includes product construction variables such as film thickness if a film is constructed. If the invention is used in retroreflective sheeting constructions the ratio of the yellow-green to perylene imide dye may also depend upon the use of backing layers used to achieve the retroreflection such as microspheres, cubes and the like which are described in more detail below. 
     Typically, between about 0.01 and about 2.00 weight percent, and preferably between about 0.05 and about 0.70 weight percent and most preferably between about 0.1 and about 0.5 weight percent of the fluorescent dye blend is contained in the article of the present invention. It will be understood that articles with dye loadings outside this range can be used in accordance with the invention. Although dye loading may vary depending upon the final application, these loadings are typical for about a 0.075 to 0.25 mm thick film. However, if the dye is added to a thicker film, lower dye loadings can give the same visual effect. As known by those in the art, articles having heavier dye loadings will exhibit brighter fluorescence and/or deeper color than will articles with lighter dye loadings of the same dye. However, articles having very high fluorescent dye loadings may exhibit a self-quenching phenomenon which occurs when molecules of the fluorescent dye absorbs the energy emitted by neighboring fluorescent dye molecules. This self-quenching causes an undesirable decrease in fluorescent brightness. 
     In some embodiments the articles of the invention are films. In yet other embodiments, these films of the invention are retroreflective. Films of the invention without opacifying agents such as titanium oxide or calcium carbonate are transparent. Such capability may be achieved as shown in FIG. 1 by forming retroreflective elements 20 on second side 16 of color layer 12, or alternatively as shown in FIG. 2 by attaching retroreflective base sheet 42 to second 36 of color layer 32, either with transparent intermediate adhesive layer 40 as shown or by laminating the base sheet and color layer in direct contact with one another (not shown). As shown in FIG. 2, retroreflective base sheet 42 comprises a member with cube-corner retroreflective elements formed on back side 46 thereof. In other embodiments, the retroreflective base sheet may comprise a microsphere-based retroreflective structure, e.g., comprising a monolayer of transparent microspheres and reflective means disposed on the opposite side of the monolayer as the color layer. For instance, a screen layer/color layer combination of the invention may be laminated to the front surface of the cover film of an encapsulated-lens retroreflective sheeting such as is disclosed in U.S. Pat. No. 3,190,178 (McKenzie) or it may even be used as the cover film of an encapsulated-lens sheeting. A screen layer is an overlay of clear polymer and may or may not include a UV-absorber and is optional in the present invention. In retroreflective embodiments, the color layer or at least that portion of it which is disposed in from the retroreflective elements, i.e., between the retroreflective elements and the screen layer, should be substantially transparent to visible light. 
     FIG. 3 illustrates another retroreflective embodiment of the invention wherein the article of the invention is a &#34;button-type&#34; retroreflector. Article 50 comprises color layer 52 with first side 54 and second side 56, screen layer 58 disposed to first side 54, and base member 60, with screen layer 58 and base member 60 enclosing color layer 52. Second side 56 has retroreflective elements 62 formed therein. Screen layer 58 and color layer 52 can be disposed spaced apart from one another as shown, or alternatively may be placed in contact with one another. Article 50 can be mounted on a backing (not shown), e.g., a sign panel, such that first side 54 is presented for viewing and retroreflective effect, with screen layer 58. 
     If desired, articles of the invention may be made in substantially rigid or flexible form. For example, in some embodiments the article may be sufficiently flexible to be wound about a mandrel having a diameter of about 1 centimeter. 
     EXAMPLES 
     The invention is further explained by the following examples which are intended as nonlimiting. Unless otherwise indicated, all amounts are expressed in parts by weight. 
     The following abbreviations are used in the examples: 
     
         ______________________________________Abbreviation   Meaning______________________________________IPP     N,N&#39;-bis(2,6-di-isopropyl)-3,4:9,10-perylenebis   (dicarboximide)PEP     N,N&#39;-bis(phenethyl)-3,4:9,10-perylenebis(dicarboximide)NOP     N,N&#39;-bis(octadecyl)-3,4:9,10-perylenebis(dicarboximide)L083    Lumogen F Yellow 083 - perylene dye from BASFSY98    CI Solvent Yellow 98 - thioxanthene dye from HoechstSY160   CI Solvent Yellow 160:1 - benzoxazol dye from BayerO8GF    Oraset Yellow 8GF - methine dye from Ciba-GeigySG4     Cl Solvent Green 4 - xanthene dye from BASFSG5     CI Solvent Green 5 - perylene dye from BASFPY101   CI Pigment Yellow 101 - azomethine dye from BASFD304    Golden Yellow D-304 - thioxanthene dye from Day-Glo   ColorSY131   Cl Solvent Yellow 131 - naphthalimide dye from Day-Glo   ColorPC      Bisphenol A polycarbonatePO      Polyolefin copolymerPMMA    PolymethylmethacrylatePEST    PolyesterPC/PEST Blend of polycarbonate and polyesterPU      PolyurethanePVC     PolyvinylchloridePVDF/   Blend of polyvinylidine fluoride and polymethyl-PMMA    methacrylate______________________________________ 
    
     Color Measurement 
     Chromaticity coordinates for samples were determined using a Labscan 6000 Speetrophotometer from Hunter Associates Laboratory, Inc. of Reston, Va. at the following settings and conditions: 
     Illuminant D 65 , 
     0/45 Geometry, and 
     CIE 2 Degree Standard Observer. 
     Fluorescence 
     Samples were viewed under daylight illumination to test if the sample films appeared fluorescent to the naked eye. The samples were considered fluorescent if they glowed along a cut edge. 
     Example 1 
     Example 1 demonstrates embodiments of the invention in a polycarbonate matrix with a range of dye loadings. 
     Films were prepared for Example 1 as follows. The fluorescent dyes were blended with polycarbonate resin pellets at the weight percent loadings indicated in Table 1. The resin pellets used were Makrolon FCR-2407 available from Bayer Corporation of Pittsburgh, Pa. The dye/resin mixture was dried overnight to remove moisture. After drying overnight, the mixture was extruded into film of about 4 mils (0.1 mm) thick using a single screw extruder with three heating zones set at 260° C., 260° C. and 304° C. and a film die set at 304° C. The extruder was a 3/4 inch single screw extruder for the Haake Rheocord as available from Haake of Karlsruhe, Germany. 
     For samples 1H, 1I and 1J the film was then laminated onto 3M Brand Scotchlite Diamond Grade Retroreflective Sheeting 3970G construction as manufactured by 3M Company of St. Paul, Minn. 
     Samples 1A through 1G were prepared by hot laminating two 4 mil (0.10 mm) colored films together and by laminating a 2 mil (0.05 mm) clear PMMA overlay to a first surface of the resulting colored film. Retroreflective elements were embossed into the second surface of the colored film. The 2 mil (0.05 mm) overlay contained 1.8 wt % Tinuvin 327 from Ciba Geigy Corp. 
     Color was determined for each sample as described above and results are shown in Table 1. Fluorescence testing was also undertaken for each sample and was observed in each sample. 
     
                       TABLE 1______________________________________                                 ChromaticitySample        Dye 1           Dye 2   CoordinatesNumber Dye 1   Weight %  Dye 2 Weight %                                 x    y______________________________________1A    IPP     0.1       SY98  0.1     0.515                                      0.4781B    PEP     0.1       SY98  0.1     0.525                                      0.4681C    NOP     0.1       SY98  0.1     0.517                                      0.4751D    NOP     0.067     SY98  0.12    0.506                                      0.4861E    NOP     0.083     SY98  0.12    0.514                                      0.4781F    NOP     0.1       SY98  0.12    0.522                                      0.4701G    NOP     0.12      SY98  0.12    0.526                                      0.4661H    NOP     0.05      SY98  0.09    0.457                                      0.4961I    NOP     0.067     SY98  0.12    0.473                                      0.4971J    NOP     0.083     SY98  0.15    0.483                                      0.496______________________________________ 
    
     Example 2 
     Example 2 demonstrates embodiments of the invention in a polymethacrylate matrix with a range of dye loadings. 
     The films for Example 2 were prepared as described in Example 1 except the polymeric matrix used was polymethyl methacrylate (PMMA) instead of polycarbonate. The PMMA used was either Perspex CP924 or CP923 from ICI Acrylics (St. Louis, Mo.) or Lucite 47K from Dupont (Wilmington, Del.), all contained roughly 0.3 wt % UV absorber of a benzotriazole type. Films were made by either extrusion or solvent casting. Extrusion temperatures for the PMMA were 249° to 260° C. Solvent cast films were made by dissolving resin and dyes in a blend of tetrabydrofuran and methyl ethyl ketone and drying slowly at room temperature. The dyes and loadings used were as indicated in Table 2. Film samples were made by laminating the 4 mil (0.10 mm) colored films to a retroreflective sheeting sample (Scotchlite Diamond Grade Sheeting 3970). The chromaticity coordinates of each sample was determined as described above and results are shown in Table 2. Fluorescence testing was also undertaken for each sample and was observed in each sample. 
     
                       TABLE 2______________________________________   Dye 1          Dye 2    CIE Chromaticity                           CoordinatesSample Dye 1   Weight % Dye 2 Weight %                               x     y______________________________________2A    IPP     0.20     D304  0.02   0.5039                                     0.47082B    IPP     0.10     PY101 0.10   0.4865                                     0.49812C    IPP     0.10     SY160 0.10   0.5082                                     0.48012D    IPP     0.10     SG4   0.10   0.4963                                     0.45732E    IPP     0.10     SY98  0.25   0.5080                                     0.47392F    IPP     0.10     D304  0.10   0.5131                                     0.4759______________________________________ 
    
     Example 3 
     Example 3 shows embodiments of the invention in a polyurethane matrix with a range of dye loadings. 
     The films for Example 3 were prepared as described in Example 1 except the polymeric matrix used was polyurethane(PUR) instead of polycarbonate. The PUR used was PN03 from Morton Intentional Inc., Seabrook, N. H. The dyes and loadings used are as indicated in Table 3. Extrusion conditions for the PUR were 154-199 degrees C. Samples were made by laminating the 4 mil (0.10 mm) colored films to retroreflective sheeting, Scotchlite Diamond Grade Sheeting 3970. Color measurements were determined for each sample as described above. Fluorescence testing was also undertaken for each sample and was observed in each sample. 
     
                       TABLE 3______________________________________   Dye 1          Dye 2    CIE Chromaticity                           CoordinatesSample Dye 1   Weight % Dye 2 Weight %                               x     y______________________________________3A    IPP     0.100    SY98  0.100  0.4954                                     0.47063B    IPP     0.080    SY98  0.120  0.5049                                     0.47683C    IPP     0.067    SY98  0.133  0.5102                                     0.4636______________________________________ 
    
     Example 4 
     Example 4 demonstrates embodiments of the invention in a polycarbonate/polyester blend matrix with a range of dye loadings. 
     The films for Example 4 were prepared as detailed in Example 1 except the polymeric matrix used was polycarbonate/polyester blend (PC/PEST) instead of polycarbonate. The PC/PEST used was DA003 from Eastman Chemical Company, Kingsport, Tenn. Extrusion conditions for the PC/PEST were 270-290 degrees C. The dyes and loadings used are as indicated in Table 4. 
     Film samples were made by laminating the 4 mil (0.10 mm) colored films to a retroreflective sheeting sample, Scotchlite Diamond Grade Sheeting 3970 available from 3M Corporation of St. Paul, Minn. Color measurements according to the protocol outlined above were taken on the resulting laminates with results shown in Table 4. Fluorescence testing was also undertaken for each sample and was observed in each sample. 
     
                       TABLE 4______________________________________   Dye 1          Dye 2    CIE Chromaticity                           CoordinatesSample Dye 1   Weight % Dye 2 Weight %                               x     y______________________________________4A    NOP     0.10     SY98  0.100  0.4895                                     0.48064B    NOP     0.07     SY98  0.128  0.4896                                     0.49334C    NOP     0.05     SY98  0.150  0.4760                                     0.50124D    NOP     0.15     SY98  0.050  0.5060                                     0.4647______________________________________ 
    
     Example 5 
     Example 5 demonstrates embodiments of the invention in a polyolefin copolymer matrix with a range of dye loadings. 
     The films for Example 5 were prepared as outlined in Example 1 except the polymeric matrix used was poly(ethylene-co-acrylic acid) EAA! instead of polycarbonate. The EAA used was Primacor 3440 from Dow Chemical Company, Midland, Mich. Extrusion conditions for the EAA were 176.7-215.6 degrees C. The dyes and loadings used are as indicated in the Table 5. 
     Film samples were made by laminating the 4 mil (0.10 mm) colored films to a retroreflective sheeting sample, Scotchlite Diamond Grade Sheeting 3970. Color measurements according to the protocol outlined above were made on the resulting laminates with results shown in Table 5. Fluorescence testing was also undertaken for each sample and was observed in each sample. 
     
                       TABLE 5______________________________________   Dye 1          Dye 2    CIE Chromaticity                           CoordinatesSample Dye 1   Weight % Dye 2 Weight %                               x     y______________________________________5A    IPP     0.10     SY98  0.10   0.4595                                     0.47525B    IPP     0.10     PYIOI 0.10   0.5103                                     0.4605______________________________________