Fluorescent red article and retroreflective article made...

Details Fluorescent red article and retroreflective article made... Fluorescent red article and retroreflective article made...

2000-09-12

2001-11-06

Phan, James (Department: 2872)

Optical: systems and elements

Signal reflector

3-corner retroreflective

C359S529000, C359S536000, C359S539000, C359S540000, C359S900000, C156S305000, C428S141000, C428S407000, C428S412000

Reexamination Certificate

active

06312132

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to fluorescent red articles and laminates which are particularly useful for improving the visibility and conspicuity.
BACKGROUND OF THE INVENTION
It is commonly known that fluorescent colors provide increased conspicuity for visual signaling under most lighting conditions, and particularly under low natural lighting conditions. These conditions occur at dusk and at sunrise and present a challenge for traffic sign manufacturers. If increased conspicuity of an article is desired, the article is often colored with fluorescent colorants. Fluorescent colors allow enhanced conspicuity because the visual contrast that the fluorescent colors create with the environment is greater than that of similar non-fluorescent articles. Fluorescent colored traffic signs are effective at increasing the conspicuity of the signs and, in turn, increase the likelihood of the signs being observed.
Certain conventions have evolved with respect to the color of traffic signs. For example, informational signs may be green or blue, caution or warning signs may be orange or yellow, and yield and stop signs are red. Motorists have become accustomed to these conventions and color purity is important to encourage the appropriate response. Although red fluorescent dyes are available, their chromaticity or color purity can vary from pink to orange in dyed articles and may not have a true red appearance.
In addition to color purity, it is important for highway signage to be visually conspicuous. As the brightness or luminance of a sign increases, the more visually obvious the sign is relative to its background. The luminance of a fluorescing article is the sum of its reflected and emitted light. The greater the contribution from emitted light to total luminescence the brighter the appearance of the fluorescing article. It is therefore desirable to avoid conditions that quench fluorescence.
Various attempts to improve the visibility of signage have been reported. Burns et al., U.S. Pat. Nos. 5,920,429, 5,754,337, and 5,674,622 disclose fluorescent yellow articles comprising two fluorescent dyes dispersed in a polymeric matrix suitable for applying to retroreflective surfaces. The resulting yellow retroreflective articles are suitable for traffic signs.
Nagaoka et al., U.S. Pat. No. 6,048,069 disclose retroreflective sheeting having image elements made from light transmitting prismatic sheeting. An adhesive layer adheres the prismatic sheeting to the retroreflective sheeting and the adhesive may contain a red fluorescent dye.
Sakaya et al., European Patent Application No. 792,907 disclose polyolefin resin films suitable for outdoor use. The films contain fluorescent substances including perylene dyes and a shielding agent to suppress the deactivation of the fluorescent substance under outdoor conditions and from other substances in the film.
Nagaoka, International Application No. PCT/US97/17457 discloses a retroreflective graphic article having an image layer disposed on a retroreflective base sheet and a dye receiving layer disposed on the image layer. The image layer contains a pigment and a fluorescent dye. The fluorescent dye migrates to the receiving layer, thereby reducing adverse effects from the pigment on the visual properties of the dye.
Smith, International Application No. PCT/AU96/00303 discloses a method for making fluorescent dye compositions useful for making luminescent sunlight collectors from a solution of a fluorescent dye and a polymerizable monomer wherein the solution is prepared without additional solvent and with the aid of ultrasonic mixing. The monomer solution is polymerized in a vertical tube to form a luminescent sunlight collector.
SUMMARY OF THE INVENTION
Fluorescent articles of the present invention provide red color fidelity substantially free of orange or pink hues. Further, the articles of the invention have a visual brightness substantially attributable to fluorescent or emitted light with respect to the total light observed from the surface of the article. Accordingly, the present invention provides fluorescent red articles suitable for applying to a reflective substrate to form a laminate, the article having a substantial fluorescence luminance with respect to the total luminance of the article. Accordingly, the present invention in one aspect is a fluorescent red article comprising a polymer matrix and a red perylene dicarboximide dye having the formula
wherein R
1
and R
2
are identical or different C
1
-C
18
is alkyl which are unsubstituted or substituted by C
1
-C
18
alkoxy, C
1
-C
18
alkanoyloxy, C
1
-C
18
alkylthio, hydroxyl, phenyl, phenoxy or phenylthio; cyclohexyl which is unsubstituted or substituted by hydroxyl, C
1
-C
5
alkyl, methoxy, ethoxy, C
1
-C
2
alkylthio, C
1
-C
18
alkanoyloxy or C
1
-C
18
alkoxycarbonyl; phenyl which is mono-substituted or di-substituted in the ortho position by C
1
-C
5
alkyl or chlorine or by C
1
-C
5
alkyl and chlorine; or naphthyl; X, Y and Z are each independently chlorine, bromine or —OR
3
, and R
3
is unsubstituted phenyl, or phenyl substituted by cyano, halogen, nitro, C
1
-C
18
alkyl or a mixture thereof, or naphthyl or anthryl; wherein the article has chromaticity coordinates (x, y) within the area defined by (0.648, 0.351), (0.735, 0.265), (0.629, 0.281) and (0.565, 0.346) in terms of the CIE 1931 Standard Colorimetric System and measured using 0/45 geometry and evaluated with CIE Standard Illuminant D65 and a fluorescence luminance factor of at least about 8.
Another aspect of the present invention is a fluorescent red article having a retroreflective side.
Yet another aspect of the present invention is a fluorescent red laminate comprising a fluorescent red article applied to a reflective substrate wherein the laminate has chromaticity coordinates (x, y) within the area defined by (0.648, 0351), (0.735, 0.265), (0.629, 0.281) and (0.565,0.346) in terms of the CIE 1931 Standard Colorimetric System and measured using 0/45 geometry and evaluated with CIE Standard Illuminant D65 and a fluorescence luminance factor of at least about 8.
The present invention is also directed to a fluorescent red retroreflective laminate which includes a fluorescent red article disposed on a retroreflective substrate having a retroreflective side.
Another aspect of the invention is a fluorescent red retroreflective sheeting comprising optical elements which comprise a polymer matrix and a dye wherein the retroreflective sheeting has chromaticity coordinates (x, y) within the area defined by (0.648, 0.351), (0.735, 0.265), (0.629, 0.281) and (0.565, 0.346) in terms of the CIE 1931 Standard Colorimetric System and measured using 0/45 geometry and evaluated with CIE Standard Illuminant D65 and a fluorescence luminance factor of at least about 8 as well as a fluorescent red retroreflective sheeting comprising optical elements and at least one layer comprising a polymer matrix and a dye wherein the retroreflective sheeting has chromaticity coordinates (x, y) within the area defined by (0.648, 0.351), (0.735, 0.265), (0.629, 0.281) and (0.565, 0.346) in terms of the CIE 1931 Standard Colorimetric System and measured using 0/45 geometry and evaluated with CIE Standard Illuminant D65 and a fluorescence luminance factor of at least about 8.
A further aspect of the invention is a method for making a fluorescent red laminate comprising the steps of preparing a mixture of a polymeric resin and a red perylene dicarboximide dye having the formula
wherein R
1
and R
2
are identical or different C
1
-C
18
alkyl which are unsubstituted or substituted by C
1
-C
18
alkoxy, C
1
-C
18
alkanoyloxy, C
1
-C
18
alkylthio, hydroxyl, phenyl, phenoxy or phenylthio; cyclohexyl which is unsubstituted or substituted by hydroxyl, C
1
-C
5
alkyl, methoxy, ethoxy, C
1
-C
2
alkylthio, C
1
-C
18
alkanoyloxy or C
1
-C
18
alkoxycarbonyl; phenyl which is mono-substituted or di-substituted in the ortho position by C
1
-C
5
alkyl or chlorine or by C
1
-C
5
alkyl and chlorine; or naphthyl; X, Y and Z are each independentl

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