1. Field of the Invention
The present invention relates generally to blends containing self-glowing phosphor and more particularly to the making and use of various forms of such blends in the darkness for visual marking and decoration without consuming electricity or chemicals.
2. Background Art
Currently people are relying on electricity for lighting. That put us in a vulnerable position when, or where there is no electricity (e.g. rural area). It also pollutes the environment since the electricity is generated mostly from burning fossil fuel, and lighting represents the biggest consumption of electricity (˜41%). The old-fashioned lighting with candle consumes material and chemical energy; it is also a “spot” lighting source with very limited brightness and reach. Question arises: Is there any “cleaner” alternative source of lighting technology?
Self-Glowing phosphors are substances that emit light after having absorbed visible or ultraviolet radiation or the like, and the afterglow of the light that can be visually observed continues for a considerable time, ranging from several minutes to several hours after the source of the stimulus is cut off. Until recently, the most commonly known non-radioactive phosphorescent phosphor pigments were sulfides of zinc, calcium, strontium and cadmium, such as CaS:Bi (which emits violet blue light), CaSrS:Bi (which emits blue light), ZnCdS:Cu (which emits yellow or orange light) and ZnS:Cu (which emits green light). The color palette of the phosphorescent afterglow, however, has been limited to these colors.
Recently, a new group of aluminate based phosphorescent phosphors (e.g. MAl2O4:Eu. Dy, M is alkali earth element) that both absorb and emit light in the visible spectrum has become available. Phosphorescent compounds with an aluminate matrix are disclosed in U.S. Pat. Nos. 5,424,006 and 5,686,022. Several follow on patents describes the use of the aluminate phosphors in making plastic composites and articles, which include:
U.S. Pat. No. 5,607,621 describes phosphorescent synthetic resin materials comprising about 5 to about 20% by weight of similar metal aluminates based phosphors and a synthetic resin. Many synthetic resins are mentioned by way of example.
U.S. Pat. No. 5,885,483 describes the compositions and the manufacturing method of long afterglow metal aluminates based phosphors.
U.S. Pat. No. 5,976,411 describes molded, extruded or formed phosphorescent plastic articles made out of a plastic composition comprising a thermoplastic or a thermosetting resin, about 1% to about 50% by weight of phosphorescent pigment and about 0.001% to about 20% by weight of a laser energy absorbing additive.
U.S. Pat. No. 6,093,346 describes the compositions and the manufacturing method of long afterglow metal silicate luminescent materials which main chemical composition formula is: aMO-bM′O-cSiO2-dR:Eux Lny.
U.S. Pat. No. 6,359,048 describes a luminescent paint by combining alkali earth oxide aluminates phosphors with an alkyd base, a rheology improver, another pigment, an anti-skin additive, and other ingredients, one can achieve a luminescent paint
U.S. Pat. No. 6,375,864 describes compositions and molded, extruded or formed phosphorescent plastic articles comprising aluminates phosphorescent phosphor pigments preferably in combination with polymer-soluble daylight fluorescent dyes.
JP-A-2000-034 414 describes semitransparent light-storing resins, which contain in total 14% by weight of aluminate light storing pigment. Upon incorporation of the pigments of JP-A-2000-034 414 in a polycarbonate resin, the favorable physical properties of the polycarbonate get lost. The aluminates particles are very hard and cause wear of the screws in injection molding machinery. The wear is so strong that graying of the composition processed with the screw may result.
U.S. Pat. Nos. 6,676,852, 6,692,659 and 6,716,368, describe transparent or translucent thermoplastic compositions comprising a thermoplastic (polycarbonate) resin and alkali earth aluminates phosphorescent pigment (phosphor).
The phosphorescent oxide pigments disclosed and used in the current plastic composites are all based on rare earth doped metal (alkali earth) aluminates. There are other phosphorescent materials that can also be effectively applied as the pigment for long afterglow composites or articles. In addition, there are many other forms and uses of phosphorescent blends that will self-glow in darkness without consuming electricity or chemicals.
The present invention discloses the use of the pigment of silicates, phosphate, borates, and their compounds with aluminates (e.g. alumino-silicates, alumino-borates, and alumino-phosphate) materials to form self-glowing phosphorescent blends with many utilities. These blends will store energy from solar light, artificial light (i.e. lamps, LED), or lasers, and emit various colors of visible light apparent to naked eye when those excitation light sources are switched off, for hours to days, without consumption of electric energy. Such optical charging and self-glowing process can be repeated for over 1000 times in the ambient temperatures and atmospheres.
In addition, the present invention relates to several forms of the new self-glowing blends. The end products of these blends include self-glowing paints, self-glowing tapes (including pressure sensitive adhesive tape), self-glowing plastic foil, self-glowing glues and sealant, self-glowing writing and printing inks, self-glowing papers and stickers, self-glowing cloth and textiles, self-glowing glass, and self-glowing plastic composites and articles. These articles can store solar, artificial light, or other form of excitation energies, and self-glow multiple colors of visible light apparent to naked eye for hours to days, when those excitation light sources are switched off, without consumption of electric energy. It can be further recharged or re-excited after the self-emitting light fades out. This energy storage-light emitting cycle can go on for years, without electricity consumption. They can be utilized as self-glowing decoration at night, they can also mark objects and directing traffic in the darkness to avoid safety hazard, they can also serve as low light lighting source.
The aforementioned objects and advantages of the present invention, as well as additional objects and advantages thereof, will be more fully understood hereinafter as a result of a detailed description of a preferred embodiment when taken in conjunction with the following drawings in which:
a and 1b illustrate charge-trapping process (
1. The Application of New Phosphorescent Oxide Pigments in the “Self-Glowing” Blends
Although any phosphors with long afterglow can be used as “self-glowing” pigment in the invention, including the long afterglow phosphors, the disclosed self-glowing phosphorescent blends use the following families of phosphor compositions as the new phosphorescent pigments in the blend with many possible forms:
a. Metal Silicates: (M1-a,M′a)m(Si1-b,Geb)Oc:Eux Lny, wherein M is one or multiple alkali earth elements from Be, Mg, Ca, Sr, Ba, and Zn; M′ include at least one elements from the group of Y, La, Sc, B, Al, Ga and P; Ln is one or more of elements from the group of Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Pb, Tl, Mn, and Bi; wherein a, b, c, m, x and y are within ranges of 0≦a≦0.9, 0≦b≦0.2, c is the value that depends on the composition of all the metal cations to balance the charge, 0.5≦m≦4, 1×10−4≦x≦2×10−1, and 1×10−4≦y≦5×10−1. Such host may also contain a halogen element such as F, Cl, Br or I in an amount within range from 1×10−5 to 1×10−1 g.atm/mol of the host material.
The oxide phosphorescent pigments disclosed and used in the current plastic composites are all based on rare earth doped metal oxide (alkali earth) aluminates pigments. Other forms of oxide phosphorescent materials are also identified as potentially efficient phosphorescent materials. Their chemical compositions have been listed in a-f in previous paragraphs. Their application in preparing and the use of the composite or blend in various forms are the basis of this disclosure. Metal silicates, borates, phosphates are effective phosphors hosts, they can also form compound with aluminates to yield effective host for phosphorescent materials. They can form various discrete phases and continuous solid solutions to effectively host the rare earth activators.
Eu2+ is a well-known activator cation, it can be excited by long wavelength UV to short wavelength visible light, which induces a 4f-5d parity allowed transition. This range of excitation spectrum overlap well with portions of the solar spectrum, and this series of phosphors can be well excited in the daylight. By systematically varying the elemental compositions, blue to green luminescence can be created from this series of phosphors. Generally, increasing the effective crystal field around the Eu activator will increase its 5d level and induce a shift of both excitation and emission to shorter wavelength. The ionic strength of related cations in these series of phosphors are in the order of Si4+>Al3+>Be2+>Mg2+>Ca2+>Sr2+>Ba2+. And more ionic strength in the lattice will increase the crystal field around Eu2+ and induce a blue shift (e.g. the emission peak of SrAl2O4:Eu2+ is ˜520 nm compared to ˜540 nm of SrGa2O4:Eu2+).
For example, the electronic energy level diagram of the alkali-earth alumino-silicates doped with Eu2+ and Dy3+ is shown in
As discussed previously, continuous emission wavelength from blue to green may be generated from the Eu2+ activator in this series of energy storage phosphors. However, three primary colors (blue, green and red) are necessary to generate the full color space, including the white color for lighting. Eu2+ is not an effective activator for red emission. The following compositions are disclosed for red emission persistent phosphors.
2. Many Forms and Utilities of the Long Afterglow Blends with the New Oxide Phosphorescent Pigments
The following paragraphs disclose concepts and methods of making several specific new products that are self-glowing in the darkness. The self-glowing blends or composites can glow in the darkness without consuming electricity or chemicals; they can be utilized in the following applications with many social benefits:
As discussed in the introduction, the inorganic phosphorescent pigments must coexist and be compatible in the blend. To maintain the integrity of a polymer coating formula, no detrimental chemical interactions among the components are allowed, those components should stay well mixed without segregation. Finally, one functional component should not shield or degrade the function of other component. The phosphorescent materials can be added as either pigment or extended pigment into some well established polymer coating system, and it also need to follow some criteria for pigments.
To maximize the hiding property of a pigment in the polymer, it needs to have dramatically different refractive index from the surrounding polymers (most polymers have refractive index around 1.5). In addition, more light-scattering results in better hiding property, and particle size similar to the light wavelength afford the highest scattering efficiency. To hide visible light, pigment should be made to be around 0.2 to 1 micron in particle diameter. Finally, extender pigment in the size of 0.2 to 1 micron can be added to ensure the optimum pigment particle separation for maximum scattering.
The phosphors can be ground into fine particles and compounded into polymer system. It can be added as the sole pigment in the paint formula, or as an extender pigment into a pigmented polymer. Due to the higher expense of the phosphors compared to regular pigment, it is more desirable to add a smaller fraction of it as extender with other pigments (e.g. TiO2, ZnO). Plus, the superior visible light reflectance property of these established white pigments will enhance the visual contrast of the persistent fluorescent emission of the phosphors in the darkness. Finally, these energy storage phosphors have good UV absorption, and they will improve the weatherability of the polymer coating.
The disclosed phosphorescent compositions in a-f should be great extender pigments in polymer coat. For example, alumino-silicate has been widely used as extender pigment, it is actually the only white mineral pigment that is naturally available with particle size below 2 micron. It has good white color, easily dispersible, and extremely inert. In addition, alkali-earth silicates are also well-known extender pigments. For example, the natural Wollastonite (CaSiO3), which has bright white color and low oil absorption, has been used as extender pigment to increase chemical stability, anticorrosion, and weathering of some polymer coating formula. The natural Talc (Magnesium silicate), is used in a wider variety of polymer coatings than any other single extender, with its superior anti-settling, dispersible properties. Therefore, the proposed energy storage phosphors in series 1, which are solid solutions of aluminum silicate and alkali earth silicates, should also be good extenders.
The refractive index of the disclosed pure oxide phosphors of a-e are around 1.5 to 1.8, which is close to that of the polymers (around 1.5), therefore, they are better used as extender pigments in polymer coat. The refractive index of the rare earth oxosulfides, are expected to be much higher than 1.5 (e.g. the refractive index of Y2O3 is around 2, which is close to that of ZnO). Therefore, the oxo-sulfides phosphors can be used as primary pigments. It may also be used as co-pigments with some white pigments such as ZnO or TiO2 in the polymer coat. Again, rare earth oxosulfides is a series of stable pigments, which is expected to be chemically compatible with polymer coating components.
The following are some formulation examples of the two different types of persistent self-glowing polymer coatings using the disclosed oxide phosphors (a-e) as pigments:
Waterborne polymer formula and powder coat formula are important because of their low VOC and environmental benefit. The brand-named chemicals used in the ingredient are commercially available materials. The persistent phosphor extender (a to e) used here can also be replaced by oxosulfide phosphors (f), or a mixture of the two series of phosphors can be used as extenders, to get some composite long after glowing color, such as white.
The long afterglow phosphors can also be dispersed into other hosts in preparing various objects that store optical energy in daytime or room light and self-glow visible light in darkness. The following will outline the manufacturing formulation and process for several other proposed self-glowing products. Essentially they are all blends or composites of some “binder” matrix with long afterglow phosphors as persistent glowing pigment.
a. Self-Glowing Adhesive Tapes:
Adhesive tape has at least two components: adhesives and backing. The backings include fabric, paper, plastic film, metal foil, foam, etc. The commonly used adhesives include block copolymers, natural rubber, silicone, polyacrylates, polyurethane, butyl rubber and polyisobutylene, other polyolefins, and styrene-butadiene rubber random polymer, etc. To make self-glowing adhesive tape, the persistent phosphor pigments can be compounded with adhesives, providing that the backing is optically transparent. The persistent pigment can also be compounded in the backing materials, or coated on the external side of the backing tape.
b. Self-Glowing Papers, Inks, Clothe and Textures
The long afterglow phosphor particles can also be dispersed and bonded in the hosts and ink solvents, papers, cloth and textures to make them “self-glowing” at night. Standard process in making pigment filled papers, inks, cloth and textures can be applied, by replacing the regular pigments with the long afterglow phosphor particles.
As further example,
It will be apparent to those with ordinary skill of the art that many variations and modifications can be made to the material composition, blend preparation methods, and final forms and uses of the blends disclosed herein without departing form the spirit and scope of the present invention. It is therefore intended that the present invention cover the modifications and variations of this invention provided that they come within the scope of the appended claims and their equivalents, I claim:
This application claims priority to the provisional application entitled “Phosphorescent Self-Glowing Blends and Their Applications”, Ser. No. 60/482,326, filed by the same subject inventors and assignee as the subject invention on Jun. 24, 2003.
Number | Date | Country | |
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60482326 | Jun 2003 | US |