Patent Issued for Durable Fluorescent Articles Having Multiple Film Layers

By a News Reporter-Staff News Editor at Journal of Engineering -- A patent by the inventor Wei, Guang-Xue (Buffalo Grove, IL), filed on May 12, 2009, was cleared and issued on December 4, 2012, according to news reporting originating from Alexandria, Virginia, by VerticalNews correspondents.

Patent number 8322868 is assigned to Avery Dennison Corporation (Pasadena, CA).

The following quote was obtained by the news editors from the background information supplied by the inventors: "Articles incorporating fluorescent colorants into polymeric matrices can be used for various applications including signage, vehicle markings, roadway markings, and other applications where high visibility is desired, such as information dissemination, visibility, visual signaling, and quick detection. The extraordinarily bright appearance of fluorescent materials is what provides this enhanced visibility, which is especially pronounced at dawn and dusk.

"Fluorescent colorants that can be potentially used in outdoor signage can have poor UV-light stability and can fade upon exposure to certain wavelengths of visible light. This can potentially degrade the long-term outdoor durability of the signage. A UV-light screening layer can be provided on a base fluorescent polymer matrix layer to mitigate exposure to UV-light and enhance outdoor durability. The UV-light screening layer can be made by dissolving UV-light absorbing compounds into a transparent polymer matrix. The screen layer contains UV absorbing compounds that absorb a defined range of UV-light (e.g., wavelength of about 290 nm to about 400 nm). The screen layer, however, does not substantially block visible light that can cause substantial fading of fluorescent colorants in the polymer matrix.

"Acrylic polymers have advantages of polymers such as polycarbonate. Typical in this regard is polymethylmethacrylate (PMMA). Compared to other polymers such as polycarbonate, such acrylics are inexpensive, easier to process and are less susceptible to UV light degradation. For example, after a few years of outdoor exposure, polycarbonate can develop a hazy and/or yellow appearance. Acrylics, however can withstand such outdoor weathering for a significantly longer time before the development of such defects.

"Although fluorescent acrylic articles appear to hold some promise, issues concerning color stabilization and/or fluorescent stabilization against ultraviolet radiation present a problem of substantial proportions. Ideally, if a solution could be found without the need for placement of a separate UV light screening and/or absorbent layer over the article, such a solution is potentially all the more valuable. Addressing these problems is needed for articles to be used under outdoor conditions which subject the article to lengthy exposure to sunlight.

"It has been suggested that there are three approaches for obtaining a desired fluorescent color in the typical instance when a given loading of available fluorescent dyes does not achieve the target fluorescent coloration. One approach is to adjust the loading quantity of the colorant.

"A second approach is to blend multiple fluorescent dyes together. Such an approach raises compatibility issues, both between the dyes themselves and between one or both of the dyes and the polymer matrix within which they would be loaded. Light durability also is an issue. Different dyes have different compatibility with different polymers due to differences between or among chemical structures. Durability of a given fluorescent colorant is different in different polymer matrices. One dye may have unfavorable interactions with another dye within a polymer matrix. Also even the same dye can have different light durability in different polymer matrices.

"The third approach is for the polymer matrix to contain a blend of non-fluorescent dye with a fluorescent dye. The issues noted above for multiple fluorescent dyes in the same polymer matrix are raised for this option as well. The issues could be even more difficult due to the typical greater chemical difference between a fluorescent dye and a non-fluorescent dye. Additionally, there is a chance that the non-fluorescent dye may interfere with the fluorescent properties of the fluorescent dye, which may dramatically reduce brightness of the sheeting. A non-fluorescent dye can quench the overall fluorescing of the fluorescent dye.

"As such, there is a need for a solution for this coloration problem."

In addition to the background information obtained for this patent, VerticalNews journalists also obtained the inventor's summary information for this patent: "The present invention relates to a fluorescent article that includes an underlayer colored fluorescent film and an overlayer colored fluorescent film that is provided over the underlayer colored film. The underlayer colored fluorescent film includes a first fluorescent colorant in an underlayer acrylic matrix. The overlayer colored fluorescent film includes a second fluorescent colorant in an overlayer acrylic matrix. The second fluorescent colorant in the overlayer film at least partially blocks light in a first wavelength range while allowing transmission of an amount of light in a second wavelength range effective to make the first fluorescent colorant fluoresce.

"In one aspect of the invention, the first fluorescent colorant has a first chemistry and the second fluorescent colorant has a second chemistry different from the first chemistry.

"In a further aspect of the invention, the fluorescent article further comprises retroreflective elements. The retroreflective elements can be formed into the surface of the underlayer colored fluorescent film opposite the overlayer fluorescent film.

"In yet another aspect of the invention, the fluorescent article comprises a cap layer that overlies the overlayer colored fluorescent film.

"A further aspect of the invention relates to a fluorescent yellow retroreflective article that includes an underlayer fluorescent yellow-green film and an overlayer fluorescent orange film provided over the underlayer fluorescent yellow-green film. The underlayer fluorescent yellow-green film includes a first fluorescent colorant within an underlayer acrylic matrix. The overlayer fluorescent orange film includes a second fluorescent colorant within an overlayer acrylic matrix.

"The fluorescent yellow-green coloration of the underlayer fluorescent yellow-green film can be provided by a fluorescent dye that includes at least one yellow-green shade dye chosen from benzothiazine, thioxanthene and benzoxanthene. The fluorescent orange coloration of the overlayer fluorescent orange film can be provided by a fluorescent dye that includes at least one of orange shade fluorescent dye and/or red shade perylene dye."

URL and more information on this patent, see: Wei, Guang-Xue. Durable Fluorescent Articles Having Multiple Film Layers. U.S. Patent Number 8322868, filed May 12, 2009, and issued December 4, 2012. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=100&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=4999&f=G&l=50&co1=AND&d=PTXT&s1=20121204.PD.&OS=ISD/20121204&RS=ISD/20121204

Keywords for this news article include: Chemicals, Chemistry, Avery Dennison Corporation.

Our reports deliver fact-based news of research and discoveries from around the world. Copyright 2012, NewsRx LLC