Compositions – Inorganic luminescent compositions with organic...
Reexamination Certificate
2001-01-18
2003-07-29
Koslow, G. Melissa (Department: 1755)
Compositions
Inorganic luminescent compositions with organic...
C252S500000, C252S513000, C428S690000
Reexamination Certificate
active
06599444
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to luminescent synthetic polymers. More particularly, the invention relates to photoluminescent, thermoluminescent and electroluminescent polymer blends useful as gel coats and as moldable resins.
2. Description of Related Art
The term “luminescenz” was first used in 1888 by Eilhardt Wiedemann, German physicist and historian of science, for “all those phenomena of light which are not solely conditioned by the rise in temperature.” By the rise in temperature, Wiedemann referred to the fact that liquids and solids emit more and more radiation of shorter and shorter wavelengths as their temperature increases, finally becoming perceptible to the eye as the material becomes red hot and then white hot. This is incandescence or “hot light,” in contrast to luminescence or “cold light.”
Examples of luminescence are the dim glow of phosphorus (a chemiluminescence), the phosphorescence of certain solids (phosphors) after exposure to sunlight, X-rays or electron beams, the transitory fluorescence of many substances when excited by exposure to various kinds of radiation, the aurora borealis and the electroluminescence of gases when carrying a current, the triboluminescence of crystals when rubbed or broken, the bioluminescence of many organisms, including the firefly, the glowworm and the “burning of the sea,” the fungus light of decaying tree trunks, and the bacterial light of dead flesh or fish.
For centuries incandescence was the universal method of artificial illumination: the torch, candle, oil lamp, gas lamp and tungsten filament served to light the way. There remains a need for a useful, renewable cold light source, particularly for photoluminescent materials which will absorb light and then emit useful amounts of light over long periods, thermoluminescent materials in which the photoluminescence is activated by heat and electroluminescent materials in which the light output is in response to electrical current.
Phosphorescent pigments are those in which excitation by a particular wavelength of visible or ultraviolet radiation results in the emission of light lasting beyond the excitation. After cessation of luminescence and renewed exposure to light, the material again absorbs light energy and exhibits the glow-in-the-dark property (an absorbing-accumulating-emitting cycle). Most phosphorescent pigments suffer from the problems of low luminescence and/or short afterglow.
Various phosphorescent substances are known, including sulfides, metal aluminate oxides, silicates and various rare earth compounds (particularly rare earth oxides). The most common type of phosphorescent pigment is zinc sulfide structure with substitution of the zinc and activation by various elemental activators. It is known that many luminescent materials may be prepared by incorporating metallic zinc sulfide (which emits green light). Moreover, with zinc sulfide a material or mixtures of materials variously termed activators, coactivators or compensators are usually employed. Known activators include such elements as copper (forming ZnS:Cu, probably the most common zinc sulfide phosphor), aluminum, silver, gold, manganese, gallium, indium, scandium, lead, cerium, terbium, europium, gadolinium, samarium, praseodymium or other rare earth elements and halogens. These activators presumably enter the crystal lattice of the host material and are responsible for imparting the luminescent properties to the material. Other sulfide phosphors which emit various colors of light include ZnCdS:Cu and ZnCdS:Ag, CaS:Bi, CaSrS:Bi, alpha barium-zinc sulfides, barium-zinc-cadmium sulfides, strontium sulfides, etc. The other important class of long-life phosphorescent pigments is the metal aluminates, particularly the alkaline earth aluminate oxides, of formula MAl
2
O
4
where M is a metal or mixture of metals. Examples are strontium aluminum oxide (SrAl
2
O
4
), calcium aluminum oxide (CaAl
2
O
4
), barium aluminum oxide (BaAl
2
O
4
) and mixtures. These aluminate phosphors, with or without added magnesium, may be further activated with other metals and rare earths.
For example, U.S. Pat. No. 5,558,817 (1996) to Bredol et al. discloses a method of manufacturing luminescent zinc sulfide of cubic structure activated by copper and aluminum, forming a material having a high x-value of the color point as well as a high luminous efficacy in conjunction with a simple manufacture. U.S. Pat. No. 3,595,804 (1971) to Martin, Jr. discloses a method for preparing zinc sulfide and zinc-cadmium sulfide phosphors containing aluminum and activated with silver or copper. U.S. Pat. No. 3,957,678 (1976) to Dikhoff et al. discloses a method of manufacturing a luminescent sulfide of zinc and/or cadmium. The luminescent sulfide may be self-activated or activated by silver, copper and/or gold and coactivated by aluminum, gallium, indium, scandium and/or the rare earths. U.S. Pat. No. 3,970,582 (1976) to Fan et al. discloses luminescent materials comprising alpha barium zinc sulfides or barium zinc cadmium sulfides activated with manganese, europium, cerium, lead or terbium and methods for making the phosphors.
Alkaline earth metal aluminate oxide phosphors and their preparation are discussed in U.S. Pat. No. 5,424,006 to Murayama et al. Alkaline earth aluminum oxide phosphors of formula MAl
2
O
4
were prepared where M was selected from calcium, strontium, barium or mixtures thereof, with or without added magnesium. The phosphorescent aluminates were activated with europium and co-activated with lanthanum, cerium, praseodymium, neodymium, samarium, gadolinium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, tin, bismuth or mixtures thereof. These metal aluminate phosphors have a bright and long-lasting photoluminescent afterglow and show a glow peak of thermoluminescence in a high-temperature region of 50° C. or above when irradiated by ultraviolet or visible rays having a wavelength of 200 to 450 nm at room temperatures.
The alkaline earth metal type aluminate phosphors of Murayama et al. were developed in response to the problems with zinc sulfide phosphors decomposing as the result of irradiation by ultraviolet (UV) radiation in the presence of moisture (thus making it difficult to use zinc sulfide phosphors in fields where it is placed outdoors and exposed to direct sunlight) and problems of insufficient length of afterglow (necessitating doping a radioactive substance to the phosphorescent phosphor and employing a self-luminous paint which keeps emitting light by absorbing radiation energy for items such as luminous clocks). The metal aluminate phosphors such as activated alkaline earth aluminate oxides exhibit UV insensitivity and bright and long-lasting afterglow luminance. However, metal aluminate phosphors may be at a disadvantage compared to zinc sulfide phosphors in requiring a considerably long time and/or more intense illumination for excitation to attain saturation of afterglow luminance and vulnerability to water and moisture. This points out is the need for adaptation of specific phosphors and mixtures of phosphors for use in varying excitation conditions, a need for water-resistant formulations suitable for protecting phosphorescent particles and a need for UV protection where sulfides are utilized.
Phosphorescent materials have found use in a variety of commercial applications including warning signs, machinery marking, dial illumination, directional signs, marking the edge of steps, fire helmets, accident prevention, protective clothing, sports equipment, etc. Commercially available sheets of phosphorescent material are typically phosphorescent pigment in clear polyvinylchloride. Other approaches are also utilized, usually involving thermoplastics (which may be repeatedly softened by heating and hardened by cooling) or elastomeric and rubbery materials. For example, U.S. Pat. No. 4,211,813 (1980) to Gravisse et al. discloses photoluminescent textile and other flexible sheet materials coated with a thin film of photoluminescent synthetic re
Hyde William R.
Koslow G. Melissa
Orion 21 A.D. Pty. Ltd.
LandOfFree
Luminescent gel coats and moldable resins does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Luminescent gel coats and moldable resins, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Luminescent gel coats and moldable resins will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3093402