Synthetic polymers with improved photo-stability by incorporation of inorganic phosphors

Abstract

Described herein is a method for improving the color stability of a synthetic polymer composition by incorporating one or more inorganic phosphor dopants into the synthetic polymer. The inorganic phosphor dopants absorb ultraviolet light and emit this ultraviolet light as down-converted visible light, thereby creating a brighter appearance in the synthetic polymer composition. Additionally, a method for preparing a synthetic polymer composition having improved color stability is described.

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims the benefit of U.S. Provisional Patent Application No. 63 / 366,582, filed on June 17, 2022, the content of which is hereby incorporated by reference in its entirety.

[0002] Field The subject matter disclosed herein generally relates to methods for improving the color stability of synthetic polymers.

Background Art

[0003] Phosphor materials have the property of emitting ultraviolet light, visible light, and infrared light under the action of external excitation means such as irradiation with electromagnetic waves (e.g., electron beams, X - rays, ultraviolet rays, visible light, etc.) or application of an electric field, and thus are used in many photoelectric converters or photoelectric conversion devices. Examples of such devices are light - emitting devices including white - light - emitting diodes, fluorescent lamps, electron - beam tubes, plasma display panels, inorganic electroluminescent displays, and scintillators. In particular, inorganic phosphors have been widely studied to meet the demand for low - voltage - stimulated lighting sources due to the increase in global energy consumption. Due to the advantages of being environmentally friendly, having a long lifespan, low energy consumption, high reliability, and high luminous efficiency, the latest white - light - emitting diodes (WLEDs) have replaced incandescent lamps with lower efficiency and conventional mercury - encapsulated fluorescent lamps.

[0004] Lanthanoids are often used as phosphors for light - emitting applications. For example, the shielded f - orbitals of praseodymium enable a long excited - state lifetime and a high luminescence yield. In fact, Pr 3+ is often a dopant ion used in red, blue, green, and ultraviolet phosphors.

Summary of the Invention

[0005] In one aspect, the subject matter disclosed herein relates to a method for improving the color stability of a synthetic polymer composition, the method comprising exposing a host material of a synthetic polymer comprising one or more inorganic phosphor dopants to ultraviolet light, wherein the one or more inorganic phosphor dopants in the host material of the synthetic polymer absorb the ultraviolet light and then emit it as down-converted visible light.

[0006] In another aspect, the subject matter disclosed herein relates to a synthetic polymer composition, the composition comprising a host material of a synthetic polymer comprising one or more inorganic phosphor dopants, wherein the one or more inorganic phosphor dopants in the host material of the synthetic polymer emit visible light down-converted by exposure to ultraviolet light, and the synthetic polymer composition exhibits mechanical properties and flammability characteristics comparable to those of a synthetic polymer composition that does not comprise one or more inorganic phosphor dopants.

[0007] In another aspect, the subject matter disclosed herein relates to a method for preparing a synthetic polymer composition, the method comprising contacting a host material of a synthetic polymer with one or more inorganic phosphor dopants to prepare an inorganic phosphor-doped synthetic polymer material, wherein the one or more inorganic phosphor dopants in the inorganic phosphor-doped synthetic polymer material can absorb ultraviolet light and then emit it as down-converted visible light.

[0008] These and other aspects are described fully herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0009]

Figure 1A

Figure 1B

Figure 2

Figure 3

Figure 4

Figure 5

DETAILED DESCRIPTION OF THE INVENTION

[0010] The subject matter described herein relates to a method for improving the color stability of a synthetic polymer material by applying the unique luminescence properties of inorganic rare earth phosphors.

[0011] Synthetic polymers such as thermoplastics generally undergo photooxidation when exposed to ultraviolet light in the presence of oxygen. When the polymer absorbs this ultraviolet radiation energy, the energy of the ultraviolet light is greater than the dissociation energy of the carbon-carbon sigma bonds in the synthetic polymer, which can lead to bond cleavage. In fact, ultraviolet light such as UV-C light has wavelengths in the range of 200 nm to 280 nm with photon energies in the range of 6.2 eV to 4.4 eV. Conversely, the bond energy of a typical carbon-carbon sigma bond is only 3.8 eV. Therefore, absorption of UV-C light in the presence of oxygen can lead to dissociative oxidation of the bonds, which changes the molecular structure of the polymer. Such structural changes often accompany undesirable visual changes in the polymer such as discoloration (yellowing) and embrittlement.

[0012] Current solutions for addressing the discoloration and embrittlement often experienced by synthetic polymers exposed to ultraviolet light include the following: (1) using polymers with higher color stability in applications with high exposure to ultraviolet light, and / or (2) incorporating ultraviolet stabilizing additives into the synthetic polymer formulation. However, synthetic polymers exhibiting satisfactory color stability may lack appropriate mechanical properties such as impact durability and chemical resistance. Furthermore, additives used to improve the color stability of synthetic polymers often reduce the mechanical properties of the material, such as tensile strength. Such additives have also been shown to reduce the flammable characteristics of the material. Thus, there is a need in the art to stabilize the color of synthetic polymers exposed to ultraviolet light without reducing other material performance characteristics.

[0013] The subject matter described herein overcomes the limitations of the prior art by incorporating inorganic phosphors into a synthetic polymer composition. The inorganic phosphors absorb ultraviolet light (103) and convert it into harmless visible light (104). The inorganic phosphors applied to the methods and compositions described herein are crystalline materials and have a lattice structure that confers high photostability, as shown by the exemplary lattice structure of FIG. 5. For example, the regular and robust arrangement of atoms within the lattice improves the thermal stability of the phosphor. In these phosphors, a small percentage of metal "dopant" ions are incorporated into the lattice that will affect the excitation and emission characteristics of the phosphor. The inorganic phosphor dopants (102) used herein refer to metal oxide or metal fluoride materials containing rare earth ions (107) or transition metals. In some embodiments, the synthetic polymer composition comprises from about 0.05 to about 10 weight percent or from about 0.05 to about 5 weight percent of an inorganic phosphor dopant. In some other embodiments, the synthetic polymer composition comprises from about 0.05 to about 0.15 weight percent, from about 0.10 to about 0.25 weight percent, from about 0.15 to about 3 weight percent, from about 0.25 to about 4 weight percent, from about 1 to about 5 weight percent, from about 1.5 to about 3.5 weight percent, from about 2.5 to about 4 weight percent, from about 0.50 to about 4.5 weight percent, from about 4 to about 5 weight percent, from about 5 to about 10 weight percent, from about 3 to about 7 weight percent, from about 4 to about 8 weight percent, from about 6 to about 9 weight percent, or from about 7 to about 10 weight percent of an inorganic phosphor dopant. Since the inorganic phosphor material is a ceramic type material, it does not adversely affect the mechanical or combustible properties of the synthetic polymer host material (101). Many phosphors strongly absorb ultraviolet light (high energy, short wavelength) (103), which is accompanied by emission of light at a longer wavelength and lower energy than the light originally absorbed by the phosphor. This emission is generally in the visible range and is not destructive to the synthetic polymer. The process by which light is absorbed at one wavelength and subsequently emitted at a longer wavelength is known as "downconversion". The inorganic phosphors in the synthetic polymers described herein absorb high energy ultraviolet light (180 nm to 360 nm) and emit the energy as "downconverted" visible light (200 nm to 700 nm), as shown, for example, by the excitation and emission spectra of the exemplary inorganic phosphors of FIG. 3.

[0014] As described herein, by incorporating different metal ions into the host lattice of a metal oxide (106) or a metal fluoride (109), the color of the emitted light energy can be adjusted. Combinations of different emission colors produce white / off-white light. For example, combinations of blue-yellow or blue-green-red emitters result in white / off-white emission. Such combinations of emissions from phosphors can be used to adjust the visual color of a solid.

[0015] The subject matter described herein manages the effect of ultraviolet light on a synthetic polymer by selective incorporation of inorganic phosphors that absorb and down-convert visible light to provide a brighter appearance to the synthetic polymer material. A brighter appearance is the brightness perceived by a viewer.

[0016] Figures 1B, 2A, and 2B illustrate exemplary methods for creating a brighter appearance on an object by applying the inorganic phosphor-doped synthetic polymer materials described herein. Briefly, as shown in Figure 1A, in step 150, one or more inorganic phosphor dopants (102) are prepared, and as shown in step 155, the one or more inorganic phosphor dopants (102) are incorporated into a host material (101) of a synthetic polymer to prepare an inorganic phosphor-doped synthetic polymer material. As shown in Figures 1B and 2A, in step 160, the inorganic phosphor-doped synthetic polymer material is exposed to ultraviolet light to charge the inorganic phosphor dopants in the material. The black and white inorganic phosphor dopants represent two different types of dopants that each emit visible light at different wavelengths. When the inorganic phosphor dopants are charged in Figure 2A, as shown in steps 165 of Figures 2B and 1B, the ultraviolet light is removed and the inorganic phosphor dopants emit visible light, thereby creating a brighter appearance on the host material of the synthetic polymer. In this example, the host material of the synthetic polymer contains two different inorganic phosphor dopants that emit light at different wavelengths and combine to form white light. The brighter appearance of the host material of the synthetic polymer is visually perceivable by an observer (shown as an eye in Figure 2B).

[0017] The following describes the subject matter disclosed herein in more detail. However, those skilled in the art related to the technology associated with the subject matter disclosed herein, who have benefited from the teachings presented in the foregoing description, will envision numerous modifications and other embodiments of the subject matter of the disclosure shown herein. Accordingly, the subject matter disclosed herein is not limited to the specific embodiments disclosed, and it is to be understood that modifications and other embodiments are intended to be included within the scope of the claims. In other words, the subject matter described herein covers all alternatives, modifications, and equivalents. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. If one or more of the incorporated references, patents, and the like differ from or conflict with this application, including but not limited to defined terms, term usage, or described techniques, this application prevails.

[0018] I. Definitions As used herein, "and / or" refers to and encompasses any and all possible combinations of one or more of the associated listed items, as well as the absence of a combination (i.e., "or") when interpreted alternatively.

[0019] The terms "approximately," "about," and "substantially" as used herein represent an amount close to the described amount that still performs or achieves the desired function. For example, in some embodiments, as the context indicates, the terms "approximately," "about," and "substantially" may refer to an amount that is less than 10% of the described amount. The term "generally" as used herein represents a value, amount, or characteristic that mainly includes or tends towards a specific value, amount, or characteristic.

[0020] As used herein, terms that include conditions, such as, among others, "can," "could," "might," "may," "e.g.," etc., are generally intended to convey that some embodiments include certain features, components, and / or steps, while other embodiments do not, unless otherwise stated or understood in the context in which they are used. Thus, such terms that include conditions generally do not intend that a feature, configuration, and / or step is required in any form in one or more embodiments, or that one or more embodiments necessarily include logic for determining whether these features, elements, and / or steps are included or implemented in any particular embodiment, regardless of the presence or absence of the author's input or prompt. The terms "consisting of" and its grammatical variations are synonymous and are used restrictively to exclude additional elements, features, acts, operations, etc. The terms "consisting essentially of" and its grammatical variations are synonymous and are semi-restrictive terms, indicating that the item of the claim is limited to the components specified in that claim and does not materially affect the basic and novel characteristics of that claim. In addition, the term "or" is used in an inclusive sense (not an exclusive sense), such that, for example, when used to connect the recited elements, the term "or" means one, some, or all of the recited components.

[0021] As used herein, "contacting" refers to contacting the host material (101) of the synthetic polymer with the inorganic phosphor dopant (102) to prepare an inorganic phosphor-doped synthetic polymer material. In an example, such contacting can be referred to as "compounding," in which the synthetic plastic melts and mixes with the additive (i.e., the inorganic phosphor dopant) to prepare a modified polymer. The synthetic polymer serves as the host material, and the inorganic phosphor dopant (102) is incorporated into this host material, for example, through the application of heat and / or pressure, as shown in FIG. 1A.

[0022] As used herein, "improving color stability" refers to extending the color life of the host material (101) of the synthetic polymer and / or reducing the incidence of yellowing of the host material (101) of the synthetic polymer caused by exposure to ultraviolet light (103). The inorganic phosphor dopant (102) in the synthetic polymer material described herein can absorb ultraviolet light (103), thereby reducing the impact of ultraviolet absorption on the color stability of the polymer. In the examples, the inorganic phosphor dopant (102) absorbs more incident ultraviolet light (103) than the host material (101) of the synthetic polymer, thereby offsetting the photooxidation and discoloration of the polymer material.

[0023] Such improved color stability can be visually measured using a control synthetic polymer not exposed to ultraviolet light ("control"), a synthetic polymer exposed to ultraviolet light ("standard"), and a synthetic polymer containing one or more inorganic phosphor dopants described herein and exposed to ultraviolet light ("test"). The color change can be easily perceived by comparing the amount of color change among the control sample, the standard sample, and the test sample. For example, a synthetic polymer containing one or more inorganic phosphor dopants (test sample) is said to have improved color stability if it exhibits no or significantly less yellowing compared to the standard sample also exposed to ultraviolet light. Both the standard and the test are compared to the control to visualize any color changes.

[0024] In addition, different phosphors can be mixed into the host material (101) of the synthetic polymer so as to emit white or off-white visible light (104), thereby creating a brighter appearance of the polymer material. The concept of generating white light by mixing phosphors that emit light at different wavelengths is similar to what is observed in the generation of white light using LEDs, as shown in FIG. 4. For example, a general white light source can be realized by mixing red light, green light, and blue light at an appropriate intensity ratio. Alternatively, a white light source can be realized by mixing yellow light and blue light at an appropriate intensity ratio. In this specification, examples are provided in which phosphors are selected and incorporated into a synthetic polymer material so as to emit light of different colors and then be combined to produce white light.

[0025] As used herein, "white light" refers to a combination of all wavelengths of electromagnetic radiation in the visible range of the spectrum, with each wavelength present in equal amounts relative to the other wavelengths. "Off-white" light refers to a combination of wavelengths within the visible range of electromagnetic radiation that is, for example, close to white light but not present in equal amounts.

[0026] As used herein, "photooxidation" refers to the degradation of the polymer surface due to the combined action of light and oxygen. Photooxidation causes the breaking of polymer chains, resulting in an increase in the vulnerability of the material.

[0027] As used herein, the terms "inorganic phosphor dopant" and "phosphor" can be used interchangeably.

[0028] II. Method for Improving Color Stability of Synthetic Polymers In some embodiments, the subject matter described herein relates to a method for improving the color stability of a synthetic polymer composition, the method comprising exposing a host material (101) of a synthetic polymer containing one or more inorganic phosphor dopants (102) to ultraviolet light (103), One or more inorganic phosphor dopants (102) in a host material (101) of a synthetic polymer absorb ultraviolet light (103) and then emit it as down-converted visible light (104).

[0029] When a phosphor is exposed to radiation, the orbital electrons within its atoms are excited to a higher energy level and emit energy as light of a specific color when returning to their original level. In fact, the scintillation process in inorganic materials is due to the electronic band structure found in crystals. Incident particles can excite electrons from the valence band to the conduction band or the exciton band (located just below the conduction band and separated from the valence band by an energy gap). This leaves a related hole in the valence band. Impurities create electron energy levels in the forbidden gap. An exciton is a loosely bound pair of an electron and a hole and spreads through the crystal lattice until it is entirely trapped by the center of an impurity. The latter then rapidly de-excites by emitting scintillation light (i.e., photons). The wavelength emitted depends on the atom itself and the surrounding crystal structure.

[0030] As described herein, one or more inorganic phosphor dopants (102) in a host material (101) of a synthetic polymer absorb ultraviolet light (103) and emit it as down-converted visible light (104). In some embodiments, the ultraviolet light (103) used to excite (charge) the orbital electrons of the inorganic phosphor dopant (102) has a wavelength between about 160 nm and 380 nm. In other embodiments, the ultraviolet light (103) is between about 160 nm and 320 nm, between about 160 nm and 260 nm, between about 160 nm and 200 nm, between about 180 nm and 240 nm, between about 200 nm and 250 nm, between about 250 nm and 380 nm, between about 210 nm and 250 nm, between about 225 nm and 260 nm, between about 230 nm and 250 nm, or between about 190 nm and 260 nm. In some other embodiments, the ultraviolet light (103) has a wavelength of about 222 nm, 254 nm, or 275 nm.

[0031] Non-limiting examples of ultraviolet light sources used to provide ultraviolet light (103) in the above method include, for example, black lights, short-wavelength ultraviolet lamps, incandescent lamps, deuterium lamps, discharge lamps, ultraviolet LEDs, pulsed xenon light, and ultraviolet lasers. For example, the ultraviolet light source can be a pulsed xenon-ultraviolet device in the form of a handheld wand. The wand can be held, for example, at a distance of 1 to 5 inches from the surface of a material containing one or more inorganic phosphor dopants (102), and the one or more inorganic phosphor dopants (102) in the host material (101) of the synthetic polymer absorb ultraviolet light (103). In another example, the ultraviolet light source used to provide ultraviolet light (103) is a deuterium lamp, which has light in the range of about 185 nm to about 400 nm.

[0032] In addition to ultraviolet light, other sources of excitation energy may be used in the methods described herein. Personal protective equipment (PPE) may be required for the operation of such energy sources.

[0033] In some embodiments of the above method for improving the color stability of a synthetic polymer composition, the absorption of ultraviolet light (103) by one or more inorganic phosphor dopants (102) reduces the photooxidation of the host material (101) of the synthetic polymer. As used herein, reducing the photooxidation of the host material (101) of the synthetic polymer refers to reducing the discoloration and / or embrittlement of the host material (101) of the synthetic polymer due to exposure to ultraviolet light (103), by the inorganic phosphor dopant (102) in the host material (101) of the synthetic polymer absorbing most of the ultraviolet light (103), rather than the host material (101) of the synthetic polymer itself. Considering that the ultraviolet absorption behavior varies among synthetic polymers, the specific reduction of photooxidation is material-dependent. Inorganic phosphor dopants (102) generally exhibit very strong absorption. Thus, the incorporation of one or more inorganic phosphor dopants (102) into the host material (101) of the synthetic polymer can reduce the photooxidation of the host material (101) of the synthetic polymer by up to 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, or 45% compared to a host material of a synthetic polymer that does not contain one or more inorganic phosphor dopants. The photooxidation of a material can be detected, for example, using infrared spectroscopy. In particular, peroxide species and carbonyl groups formed by photooxidation often have distinct absorption bands.

[0034] In some embodiments of the method for improving the color stability of a synthetic polymer, the visible light (104) emitted by one or more inorganic phosphor dopants (102) creates a brighter appearance for the synthetic polymer composition. The brighter appearance is perceived by a viewer observing the synthetic polymer composition. In fact, as used herein, "brightness" is an attribute of visual perception such that a light source appears to be emitting or reflecting light. Brightness is the perception created by the luminance of the object of vision. In some embodiments, the inorganic phosphor dopant (102) can emit blue visible light (104) having a wavelength between 450 nm and 495 nm. The blue visible light (104) emitted from the synthetic polymer composition comprising one or more inorganic phosphor dopants can visually offset the yellow discoloration of the host material (101) of the synthetic polymer. The foregoing effect is similar to the effect of broad-spectrum visible light emission, where certain dopants in a material that emits broad-spectrum light have the effect of making the overall material appear visually brighter.

[0035] In some embodiments of the method for improving the color stability of a synthetic polymer, the light emitted by one or more inorganic phosphor dopants (102) in the host material (110) of the synthetic polymer is down-converted visible light (104). In some embodiments of the above method, one or more inorganic phosphor dopants (102) emit visible light (104) having a wavelength between about 200 and 700 nm. In other embodiments, one or more inorganic phosphor dopants (102) are between about 400 nm and 495 nm, between about 620 nm and 700 nm, between about 590 nm and 620 nm, between about 570 nm and 590 nm, between about 495 nm and 570 nm, between about 390 nm and 450 nm, between about 380 nm and 600 nm, between about 350 nm and 460 nm, between about 600 nm and 700 nm, between about 450 nm and 600 nm, between about 200 nm and 280 nm, between about 450 nm and 495 nm, between about 380 nm and 450 nm, between about 200 nm and 270 nm, between about 200 nm and 250 nm, between about 225 nm and 250 nm, between about 200 nm and 225 nm, between about 200 nm and 275 nm, or between about 225 nm and 275 nm and emit visible light (104). The specific wavelength or range of wavelengths can be selected based on the desired color of the emitted light. For example, if it is desired for the inorganic phosphor dopant (102) to emit blue light, a phosphor that emits visible light (104) having a wavelength between about 400 nm and 495 nm will be selected. In some other embodiments, if it is desired for the inorganic phosphor dopant (102) to emit green light, a phosphor that emits visible light (104) having a wavelength between about 495 and 570 nm will be selected. In other embodiments, if it is desired for the inorganic phosphor dopant (102) to emit purple light, a phosphor that emits visible light (104) having a wavelength between about 380 nm and 450 nm will be selected. In some other embodiments, if it is desired for the inorganic phosphor dopant (102) to emit yellow light, a phosphor that emits visible light (104) having a wavelength between about 570 nm and 590 nm will be selected.In a further embodiment, if it is desirable for the inorganic phosphor dopant (102) to emit orange light, a phosphor that emits visible light (104) having a wavelength between about 590 nm and 620 nm will be selected. Further, in other embodiments, if it is desirable for the inorganic phosphor dopant (102) to emit red light, a phosphor that emits visible light (104) having a wavelength between about 620 nm and 700 nm will be selected.

[0036] In some embodiments of the method for improving the color stability of a synthetic polymer, the host material (110) of the synthetic polymer comprises two or more inorganic phosphor dopants (102), and the down-converted visible light (104) emitted by the two or more inorganic phosphor dopants (102) combines to produce white or off-white light. In some embodiments of the method for improving the color stability of a synthetic polymer, the host material (110) of the synthetic polymer comprises three or more inorganic phosphor dopants (102), and the down-converted visible light (104) emitted by the three or more inorganic phosphor dopants (102) combines to produce white or off-white light. For example, an inorganic phosphor dopant (102) that emits blue visible light (104) having a wavelength between about 450 nm and 495 nm can be inserted into the host material (101) of the synthetic polymer together with a second inorganic phosphor dopant (102) that emits yellow visible light (104) having a wavelength between about 570 nm and 590 nm. The combination of the blue and yellow visible light (104) emitted by the first and second inorganic phosphor dopants (102) produces white or off-white emission (white visible light (104)). Similarly, a first inorganic phosphor dopant (102) that emits blue visible light (104) having a wavelength between about 450 nm and 495 nm can be inserted into the host material (101) of the synthetic polymer together with a second inorganic phosphor dopant (102) that emits green visible light (104) having a wavelength between about 495 nm and 570 nm, and a third inorganic phosphor dopant (102) that emits red visible light (104) having a wavelength between about 620 nm and 750 nm. The combination of the blue, green, and red visible light (104) emitted by the first, second, and third inorganic phosphor dopants (102) will produce white or off-white emission (white visible light (104)).

[0037] In some embodiments of the method for improving the color stability of a synthetic polymer, the host material (101) of the synthetic polymer is thermoplastic or thermosetting. In some embodiments, the host material (101) of the synthetic polymer is selected from the group consisting of tetrafluoroethylene, polyvinyl fluoride, polyurethane, polyester, epoxy, phenol, vinyl ester, polyamide, polyamide-imide, polyetherimide, polyvinyl chloride, polyether ketone ketone, polycarbonate, polyphenyl sulfone, polymethyl methacrylate, polyacrylate, and benzoxazine. In particular, fluorine is known to be highly resistant to photooxidation because of its high electronegativity and its tendency to accept electrons. Thus, in some embodiments, fluorinated synthetic polymers such as tetrafluoroethylene or polyvinyl fluoride are useful as synthetic polymers in the methods described herein. In addition, thermosetting polymers are generally known to have a high degree of crosslinking compared to other types of polymers, which further enhances their resistance to photooxidation.

[0038] In some embodiments of the method for improving the color stability of a synthetic polymer, the inorganic phosphor dopant (102) is a metal oxide (106) or metal fluoride (109) containing rare earth ions (107) or transition metal ions. The rare earth ions (107) or transition metal ions are referred to as "activator ions". As used herein, an "activator ion" is an ion that is added as a dopant to the crystal structure. The activator ions are surrounded by host crystal ions and form the luminescence centers where the excitation-emission process of the phosphor occurs. The wavelength emitted by the activator ions depends on the ion itself, its electron coordination, and the surrounding crystal structure. In some embodiments, the rare earth ions (107) are lanthanide ions. In some embodiments, the rare earth ions (107) are m 3+ , Pr 3+ , Ho 3+ , Er 3+ , Sm 3+ , Nd 3+ , Yb 3+ , Eu 3+ , Eu 2+ , Gd 3+ , Ce3+ , Ce 2+ , Tb 3+ , Tb 4+ , Dy 3+ , Yb 3+ , Y 3+ , and Lu 3+ In some embodiments, the inorganic phosphor dopant (102) is selected from the group consisting of Pr 3+ , Ce 3+ ,EU 3+ ,EU 2+ , Gd 3+ , Tb 3+ , and Dy 3+ , or mixtures thereof. In some embodiments, the inorganic phosphor dopant is a metal oxide (106) or metal fluoride (109) containing rare earth ions (107) selected from the group consisting of ... 3+ is expected to emit red-orange visible light with a wavelength of about 611 nm (104), and Eu doped in InBO 3+ is expected to emit yellow visible light (104) having a wavelength of about 588 nm. 16 O 27 Eu doped in 2+ can be selected, which is expected to emit blue visible light (104) having a wavelength of about 450 nm.

[0039] In some embodiments of the method for improving the color stability of a synthetic polymer, the inorganic phosphor dopant (102) is a metal fluoride (109) selected from the group consisting of Cs2NaYF6, NaCeF4, NaYF4, and NaGd4, which contains rare earth ions (107) or transition metal ions. Such metal fluoride hosts often have the characteristics of a large bandgap, structural defects that are likely to act as electron traps, and anionic defects that make them useful for inorganic phosphors.

[0040] In some embodiments of the method for improving the color stability of a synthetic polymer, the inorganic phosphor dopant (102) is a metal oxide (106) selected from the group consisting of silicates, phosphates, borates, oxides, oxynitrides, oxysulfides, and aluminates, or combinations thereof. In some embodiments, the silicate is selected from the group consisting of melilite, cyclic silicate, silicate garnet, oxyorthosilicate, and orthosilicate. Non-limiting examples of silicates include Sr2MgSi2O7, Ca2Al2SiO7, SrAl2O4, MgSiO3, SrSiO3, CdSiO3, Ba2SiO4, BaMg2Si2O7, Ca2MgSi2O7, Sr 0.5 Ca 1.5 MgSi2O7,(Ca,Sr)2MgSi2O7, Sr3MgSi2O8, Sr2MgSi2O7, Ca 0.5 Sr 1.5 Al2SiO7, Sr3Al 10 SiO 20 and Y2SiO5 are included. Non-limiting examples of borates include YBO3, InBO3, and CaAl2B2O7. Non-limiting examples of oxynitrides include MSi2O2N2 (M is Ba, Sr, or Ca). Non-limiting examples of phosphates include YPO4 and Zn3(PO4)2. Non-limiting examples of oxides include CaO, SrO, BaO, Y3Ga5O 12 , NaGdGeO4, Cd3Al2Ge3O 12 , CaTiO3, Ca 0.8 Zn 0.2 TiO3, and Ca2Zn4Ti 15 O 36is included. Non-limiting examples of oxysulfides include Y2O2S, Gd2O2S, and Sr5Al2O7S. Non-limiting examples of aluminates include MgAl2O 4、 CaAl2O4, SrAl2O4, and Sr4Al 14 O 25 is included.

[0041] In some embodiments, the host material (101) of the synthetic polymer includes two different inorganic phosphor dopants (102), and each inorganic phosphor dopant (102) is a metal oxide (106) or a metal fluoride (109) containing rare earth ions (107). The combined emission of the two inorganic phosphor dopants (102) produces white or off-white visible light (104). In some embodiments, the host material (101) of the synthetic polymer includes two different inorganic phosphor dopants (102), and the two different inorganic phosphor dopants (102) are metal oxides (106) containing rare earth ions (107). As an example, the host material (101) of the synthetic polymer can include a first inorganic phosphor dopant (102) of Y2SiO5:Ce(III) that emits blue visible light (104) having a wavelength of about 400 nm and a second inorganic phosphor dopant (102) of InBO3:Eu(III) that emits yellow visible light (104) having a wavelength of about 588 nm. The combined visible light produces white or off-white visible light (104).

[0042] In some embodiments, the host material (101) of the synthetic polymer includes three different inorganic phosphor dopants (102), and each inorganic phosphor dopant (102) is a metal oxide (106) or a metal fluoride (109) containing rare earth ions (107). The combined emission of the three inorganic phosphor dopants (102) produces white or off-white visible light (104). For example, in some embodiments, the host material (101) of the synthetic polymer emits blue visible light (104) having a wavelength of about 450 nm, such as BaMg2Al 16 O 27:It can include a first inorganic phosphor dopant (102) of Eu(II), a second inorganic phosphor dopant (102) of Y2SiO5:Tb(III) that emits green visible light (104) having a wavelength of about 545 nm, and a third inorganic phosphor dopant (102) of Y2O3:Eu(III) that emits red visible light (104) having a wavelength of about 611 nm. The combined visible light produces white or off-white visible light (104).

[0043] In some embodiments of a method for improving the color stability of a synthetic polymer composition, the synthetic polymer composition is a substrate or surface located inside an airplane. In some other embodiments, the synthetic polymer composition is a substrate or surface located in a hospital or other medical facility, a school, a gymnasium, or an automobile.

[0044] In some embodiments of a method for improving the color stability of a synthetic polymer composition, exposing a host material (101) of a synthetic polymer containing one or more inorganic phosphor dopants (102) to ultraviolet light (103) is carried out for a time sufficient to change one or more inorganic phosphor dopants (102) in the host material (101) of the synthetic polymer. In some embodiments, a time sufficient to change one or more inorganic phosphor dopants (102) in the host material (101) of the synthetic polymer is about 5 minutes, 10 minutes, 15 minutes, 20 minutes, 30 minutes, 45 minutes, 1 hour, 2 hours, 3 hours, 5 hours, 7 hours, 10 hours, 15 hours, 20 hours, or 24 hours.

[0045] One or more inorganic phosphor dopants (102) absorb ultraviolet light (103) and emit the ultraviolet light (103) as down-converted visible light (104) generally over a time on the order of nanoseconds. Further, in an embodiment, the phosphor absorbs energy and does not immediately emit light. Rather, in an embodiment, the energy dissipates in picoseconds to a lowest excited state prior to emission. In some embodiments, with the application of continuous illumination, for example, one or more inorganic phosphor dopants (102) absorb ultraviolet light (103) and continuously emit the ultraviolet light as down-converted visible light (104).

[0046] In some other embodiments, persistent phosphors can be applied to the above method for improving the color stability of the synthetic polymer composition. Persistent phosphors exhibit luminescence that persists from a few seconds to several hours after excitation ceases, which is different from normal conversion phosphors. The reason for such delayed emission is probably its ability to store energy in defects other than luminescent "activator" ions in the material. Such defects are called traps because charge carriers derived from luminescent ions are locally trapped in the defects. When sufficient energy is supplied to the trapped charge, the charge is released. After recombination at the luminescent ions, delayed emission, generally called afterglow, occurs. The time width of the afterglow can be adjusted because it depends on the so-called trap depth, which is usually investigated by thermoluminescence. For example, it is understood that shallow traps are easily emptied, but deep traps are difficult to empty at room temperature and a portion of the trapped photons remain stored there. If the trap is too deep, the trapped electrons cannot escape, preventing persistent afterglow. Thermoluminescence can be used to evaluate the trap depth. In fact, the glow curve of thermoluminescence represents the luminescence intensity versus temperature, and each glow peak is associated with a recombination center and is related to a specific trap. The glow curve can provide useful information about the material. The activation energy and escape frequency coefficient can be calculated, for example, from the glow curve. Many methods such as the initial rise method and variable heating rate can be used to calculate trap parameters based on the kinetic order of the glow peak. The luminescence efficiency of the material can be obtained based on the glow curve.

[0047] The change in the structure-luminescence characteristics of the material can be observed through the change in its glow curve. The decrease in the thermoluminescence intensity may be due to, for example, the suppression of traps. In other embodiments, adding impurities (such as another ion) to the phosphor may increase the luminescence efficiency of the material. The presence of such impurities can change the trap distribution and may deepen the trap sites caused by the change in the energy gap of the phosphor. The thermoluminescence glow curve can be obtained using a thermoluminescence meter such as the FJ-427A TL meter.

[0048] In some other embodiments, the electronic transitions of the phosphor can be characterized as "forbidden." Forbidden transitions are spectral lines associated with the absorption or emission of photons by nuclei or atoms that occur via transitions that are not permitted by certain selection rules but are permitted when the approximations associated with those rules are not made. For example, according to normal approximations (such as the electric dipole approximation for interaction with light), the process cannot occur, but in situations where it occurs with a higher level of approximation (i.e., magnetic dipole), the process becomes possible at a lower rate. One example of such a forbidden transition is observed in phosphorescent, glow-in-the-dark materials that absorb light and form an excited state whose decay involves a spin flip that is forbidden by electric dipole transitions. As a result, light is emitted slowly over minutes or hours. In fact, "forbidden" transitions occur at a much lower rate than "allowed" transitions. "Allowed" transitions are those that follow appropriate (1) spin and (2) Laporte (orbital) selection rules, exhibit a change in parity (symmetry) during the transition, emit photons with energy matching the gap between the ground state and the excited state, and exhibit a change in dipole moment. The allowed spin selection rule stipulates that the orientation of the spin does not change (i.e., no spin inversion occurs during the electronic transition). According to the Laporte selection rule, in a centrosymmetric environment, transitions between like atomic orbitals such as s-s, p-p, d-d, or f-f transitions are forbidden. Even if a transition is forbidden, it is often coupled with a vibrational factor, for example, reducing the molecular symmetry of the system and making a previously forbidden transition allowed due to the symmetry reduction. As a result, weakly allowed transitions often occur and the transition rate decreases. The typical luminescence lifetime of a material undergoing a forbidden transition can be in the milliseconds or, in some cases, seconds.

[0049] As described above, one or more inorganic phosphor dopants (102) can be used to adjust the emissivity to longer or shorter wavelengths and, in some embodiments, to create white light.

[0050] In some embodiments of a method for improving the color stability of a synthetic polymer composition, the host material (101) of the synthetic polymer is a thermoplastic material, the thermoplastic material is polyvinyl fluoride, the host material (101) of the synthetic polymer comprises two inorganic phosphor dopants (102), the first inorganic phosphor dopant (102) is Y2SiO5:Ce(III) that emits blue visible light (104) having a wavelength of about 400 nm, and the second inorganic phosphor dopant (102) is InBO3:Eu(III) that emits yellow visible light (104) having a wavelength of about 588 nm. The phosphors in the thermoplastic host material are exposed to ultraviolet light (103) for approximately 10 minutes using a xenon-ultraviolet wand before emitting visible light (104), and these are combined to produce white visible light (104).

[0051] III. Synthetic Polymer Composition with Improved Color Stability In some embodiments, the subject matter described herein relates to a synthetic polymer composition having improved color stability, the composition comprising a host material (101) of a synthetic polymer comprising one or more inorganic phosphor dopants (102), wherein the one or more inorganic phosphor dopants (102) in the host material (101) of the synthetic polymer emit visible light (104) down-converted by exposure to ultraviolet light (103), comprising the host material (101) of the synthetic polymer the synthetic polymer composition exhibits mechanical and flammability properties comparable to those of a synthetic polymer composition that does not contain one or more inorganic phosphor dopants.

[0052] As used herein, when a synthetic polymer composition exhibits "comparable" mechanical and flammability properties to a synthetic polymer composition, a synthetic polymer composition containing one or more inorganic phosphor dopants retains mechanical and flammability properties suitable for the intended use of the material. As used herein, the mechanical properties of a synthetic polymer composition can refer, in particular, to its impact durability, tensile strength, and chemical resistance. In some embodiments, the presence of one or more inorganic phosphor dopants (102) can enhance the combustion performance of the host material (101) of the synthetic polymer.

[0053] In some embodiments of the synthetic polymer composition having improved color stability, the host material (101) of the synthetic polymer is thermoplastic or thermosetting. In some embodiments, the host material (101) of the synthetic polymer is selected from the group consisting of tetrafluoroethylene, polyvinyl fluoride, polyurethane, polyester, epoxy, phenol, vinyl ester, polyamide, polyamide-imide, polyetherimide, polyvinyl chloride, polyether ketone ketone, polycarbonate, polyphenyl sulfone, polymethyl methacrylate, polyacrylate, and benzoxazine. In particular, fluorine is known to be highly resistant to photooxidation because of its high electronegativity and tendency to accept electrons. Thus, in some embodiments, fluorinated synthetic polymers such as tetrafluoroethylene or polyvinyl fluoride are useful as synthetic polymers in the methods described herein.

[0054] In some embodiments of the synthetic polymer composition having improved color stability, the inorganic phosphor dopant (102) is a metal oxide (106) or metal fluoride (109) containing rare earth ions (107) or transition metal ions. In some embodiments, the rare earth ions (107) are lanthanide ions. In some embodiments, the rare earth ions (107) are m 3+ , Pr 3+ , Ho 3+ , Er 3+ , Sm 3+ , Nd 3+ , Yb 3+ , Eu 3+, Eu 2+ , Gd 3+ , Ce 3+ , Ce 2+ , Tb 3+ , Tb 4+ , Dy 3+ , Yb 3+ , Y 3+ , and Lu 3+ , or is selected from the group consisting of combinations thereof. In some embodiments, the inorganic phosphor dopant is Pr 3+ , Ce 3+ , Eu 3+ , Eu 2+ , Gd 3+ , Tb 3+ , and Dy 3+ , or a metal oxide (106) or metal fluoride (109) containing a rare earth ion (107) selected from the group consisting of mixtures thereof. In some embodiments, the inorganic phosphor dopant is a metal oxide (106). The rare earth ion (107) is selected in combination with the metal oxide (106) to prepare a phosphor that will emit visible light (104) having a specific color and wavelength. For example, Eu 3+ doped in Y2O3 is expected to emit red - orange visible light (104) having a wavelength of about 611 nm, and Eu 3+ doped in InBO3 is expected to emit yellow visible light (104) having a wavelength of about 588 nm. In another embodiment, Eu 16 doped in BaMg2Al 27 O 2+ can be selected, which is expected to emit blue visible light (104) having a wavelength of about 450 nm.

[0055] In some embodiments of the synthetic polymer composition having improved color stability where the inorganic phosphor dopant (102) is a metal oxide (106), the metal oxide (106) is selected from the group consisting of silicates, phosphates, borates, oxides, oxynitrides, oxysulfides, and aluminates, or combinations thereof. Since such metal oxides (106) are ceramic materials, they exhibit several advantages including chemical, thermal, and photochemical stability as a result of their robust lattice structures. In some embodiments, the silicate is selected from the group consisting of melilite, cyclo-silicate, silicate garnet, oxyorthosilicate, and orthosilicate. Non-limiting examples of silicates include Sr2MgSi2O7, Ca2Al2SiO7, SrAl2O4, MgSiO3, SrSiO3, CdSiO3, Ba2SiO4, BaMg2Si2O7, Ca2MgSi2O7, Sr 0.5 Ca 1.5 MgSi2O7, (Ca,Sr)2MgSi2O7, Sr3MgSi2O8, Sr2MgSi2O7, Ca 0.5 Sr 1.5 Al2SiO7, Sr3Al 10 SiO 20 , and Y2SiO5. Non-limiting examples of borates include YBO3, InBO3, and CaAl2B2O7. Non-limiting examples of oxynitrides include MSi2O2N2 (where M is Ba, Sr, or Ca). Non-limiting examples of phosphates include YPO4 and Zn3(PO4)2. Non-limiting examples of oxides include CaO, SrO, BaO, Y3Ga5O 12 , NaGdGeO4, Cd3Al2Ge3O 12 , CaTiO3, Ca 0.8 Zn 0.2 TiO3, and Ca2Zn4Ti 15 O 36 . Non-limiting examples of oxysulfides include Y2O2S, Gd2O2S, and Sr5Al2O7S. Non-limiting examples of aluminates include MgAl2O 4、 CaAl2O4, SrAl2O4, and Sr4Al 14 O 25 .

[0056] In some embodiments of the synthetic polymer composition having improved color stability, the inorganic phosphor dopant (102) contains rare earth ions (107) or transition metal ions and is a metal fluoride (109) selected from the group consisting of Cs2NaYF6, NaCeF4, NaYF4, and NaGd4. Such metal fluoride hosts often have the characteristics of a large bandgap, structural defects that are likely to act as electron traps, and anionic defects that make it useful for inorganic phosphors.

[0057] In some embodiments of the synthetic polymer composition having improved color stability, the synthetic polymer material contains two different inorganic phosphor dopants (102), and each inorganic phosphor dopant is a metal oxide (106) or a metal fluoride (109) containing rare earth ions (107), and the combined emission of the two inorganic phosphor dopants (102) generates white or off-white visible light (104). In some embodiments, the synthetic polymer material contains two different inorganic phosphor dopants (102), and each inorganic phosphor dopant is a metal oxide (106) containing rare earth ions (107), and the combined emission of the two inorganic phosphor dopants (102) generates white or off-white visible light (104). For example, in some embodiments, the host material (101) of the synthetic polymer can include a first inorganic phosphor dopant of Y2SiO5:Ce(III) that emits blue visible light (104) having a wavelength of about 400 nm and a second inorganic phosphor dopant of InBO3:Eu(III) that emits yellow visible light (104) having a wavelength of about 588 nm. The combined visible light produces white or off-white visible light (104).

[0058] In some embodiments, the composite polymer material includes three different inorganic phosphor dopants (102), each inorganic phosphor dopant being a metal oxide (106) or a metal fluoride (109) containing rare earth ions (107), and the combined emission of the three inorganic phosphor dopants (102) produces white or off-white visible light (104). In some embodiments, the composite polymer material includes three different inorganic phosphor dopants (102), each inorganic phosphor dopant being a metal oxide (106) containing rare earth ions (107), and the combined emission of the three inorganic phosphor dopants (102) produces white or off-white visible light (104). For example, the host material (101) of the composite polymer emits blue visible light (104) having a wavelength of about 450 nm, BaMg2Al 16 O 27 :Eu(II), a first inorganic phosphor dopant; Y2SiO5:Tb(III), a second inorganic phosphor dopant that emits green visible light (104) having a wavelength of about 545 nm; and Y2O3:Eu(III), a third inorganic phosphor dopant that emits red visible light (104) having a wavelength of about 611 nm. The combined visible light produces white or off-white visible light (104).

[0059] In some embodiments of the composite polymer composition having improved color stability, the composite polymer composition includes a substrate or surface located inside an airplane. Other non-limiting examples of locations where the substrate or surface can be located include stadiums, schools, medical facilities, or automobiles.

[0060] In some embodiments of the synthetic polymer composition, one or more inorganic phosphor dopants (102) in the host material (101) of the synthetic polymer emit down-converted visible light (104) upon exposure to ultraviolet light (103). In some other embodiments of the synthetic polymer composition, one or more inorganic phosphor dopants (102) emit light having a wavelength between about 200 and 700 nm. In other embodiments, one or more inorganic phosphor dopants (102) emit visible light (104) having a wavelength between about 400 nm and 500 nm, between about 620 nm and 700 nm, between about 590 nm and 620 nm, between about 570 nm and 590 nm, between about 495 nm and 570 nm, between about 390 nm and 450 nm, between about 380 nm and 600 nm, between about 350 nm and 460 nm, between about 600 nm and 700 nm, between about 450 nm and 600 nm, between about 200 nm and 280 nm, between about 450 nm and 495 nm, between 200 nm and 270 nm, between about 200 nm and 250 nm, between about 225 nm and 250 nm, between about 200 nm and 225 nm, between about 200 nm and 275 nm, or between about 225 nm and 275 nm.

[0061] In some embodiments of the synthetic polymer composition, the host material (101) of the synthetic polymer is a thermoplastic material, the thermoplastic material is polyvinyl fluoride, the host material contains two inorganic phosphor dopants (102), the first inorganic phosphor dopant is Y2SiO5:Ce(III) that emits blue visible light (104) having a wavelength of about 400 nm, and the second inorganic phosphor dopant is InBO3:Eu(III) that emits yellow visible light (104) having a wavelength of about 588 nm.

[0062] IV. Method for preparing a synthetic polymer composition having improved color stability In some embodiments, the subject matter disclosed herein relates to a method for preparing a synthetic polymer composition having improved color stability, the method comprising contacting a host material (101) of a synthetic polymer with one or more inorganic phosphor dopants (102) to prepare an inorganic phosphor-doped synthetic polymer material, wherein the one or more inorganic phosphor dopants (102) in the inorganic phosphor-doped synthetic polymer material can absorb ultraviolet light (103) and then emit the ultraviolet light as down-converted visible light (104).

[0063] In some embodiments of a method for preparing a synthetic polymer composition having improved color stability, one or more inorganic phosphor dopants (102) can emit ultraviolet light as down-converted visible light (104). In some other embodiments of a method for preparing a synthetic polymer composition having improved color stability, one or more inorganic phosphor dopants (102) emit light having a wavelength between about 200 and 700 nm. In other embodiments, one or more inorganic phosphor dopants (102) emit visible light (104) having a wavelength between about 400 nm and 500 nm, between about 620 nm and 700 nm, between about 590 nm and 620 nm, between about 570 nm and 590 nm, between about 495 nm and 570 nm, between about 390 nm and 450 nm, between about 380 nm and 600 nm, between about 350 nm and 460 nm, between about 600 nm and 700 nm, between about 450 nm and 600 nm, between about 200 nm and 280 nm, between about 450 nm and 495 nm, between 200 nm and 270 nm, between about 200 nm and 250 nm, between about 225 nm and 250 nm, between about 200 nm and 225 nm, between about 200 nm and 275 nm, or between about 225 nm and 275 nm.

[0064] In some embodiments of a method for preparing a synthetic polymer composition having improved color stability, the host material (101) of the synthetic polymer is thermoplastic or thermosetting. In some embodiments, the host material (101) of the synthetic polymer is selected from the group consisting of tetrafluoroethylene, polyvinyl fluoride, polyurethane, polyester, epoxy, phenol, vinyl ester, polyamide, polyamide-imide, polyetherimide, polyvinyl chloride, polyether ketone ketone, polycarbonate, polyphenyl sulfone, polymethyl methacrylate, polyacrylate, and benzoxazine.

[0065] In some embodiments of a method for preparing a synthetic polymer composition having improved color stability, the inorganic phosphor dopant is a metal oxide (106) or a metal fluoride (109) containing rare earth ions (107) or transition metal ions. In some embodiments, the rare earth ions (107) are lanthanide ions. In some embodiments, the rare earth ions (107) are m 3+ , Pr 3+ , Ho 3+ , Er 3+ , Sm 3+ , Nd 3+ , Yb 3+ , Eu 3+ , Eu 2+ , Gd 3+ , Ce 3+ , Ce 2+ , Tb 3+ , Tb 4+ , Dy 3+ , Yb 3+ , and Lu 3+ , or a combination thereof. In some embodiments, the inorganic phosphor dopant is a metal oxide (106) containing rare earth ions (107) selected from the group consisting of Pr 3+ , Ce 3+ , Eu 3+ , Eu 2+ , Gd 3+ , Tb 3+ , and Dy 3+ , or a mixture thereof.

[0066] In some embodiments of a method for preparing a synthetic polymer composition having improved color stability, the inorganic phosphor dopant (102) is a metal oxide (106), and the metal oxide (106) is selected from the group consisting of silicates, phosphates, borates, oxides, oxynitrides, oxysulfides, and aluminates, or combinations thereof. In some embodiments, the silicate is selected from the group consisting of melilite, cyclo-silicate, silicate garnet, oxyorthosilicate, and orthosilicate. Non-limiting examples of silicates include Sr2MgSi2O7, Ca2Al2SiO7, SrAl2O4, MgSiO3, SrSiO3, CdSiO3, Ba2SiO4, BaMg2Si2O7, Ca2MgSi2O7, Sr 0.5 Ca 1.5 MgSi2O7, (Ca,Sr)2MgSi2O7, Sr3MgSi2O8, Sr2MgSi2O7, Ca 0.5 Sr 1.5 Al2SiO7, Sr3Al 10 SiO 20 and Y2SiO5. Non-limiting examples of borates include YBO3, InBO3, and CaAl2B2O7. Non-limiting examples of oxynitrides include MSi2O2N2 (where M is Ba, Sr, or Ca). Non-limiting examples of phosphates include YPO4 and Zn3(PO4)2. Non-limiting examples of oxides include CaO, SrO, BaO, Y3Ga5O 12 , NaGdGeO4, Cd3Al2Ge3O 12 , CaTiO3, Ca 0.8 Zn 0.2 TiO3, and Ca2Zn4Ti 15 O 36 . Non-limiting examples of oxysulfides include Y2O2S, Gd2O2S, and Sr5Al2O7S. Non-limiting examples of aluminates include MgAl2O 4、 CaAl2O4, SrAl2O4, and Sr4Al 14 O 25 .

[0067] In some embodiments of a method for preparing a synthetic polymer composition having improved color stability, the synthetic polymer material comprises two different inorganic phosphor dopants (102), each inorganic phosphor dopant being a metal oxide (106) or a metal fluoride (109) containing rare earth ions (107), and the combined emission of the two inorganic phosphor dopants (102) produces white or off-white visible light (104). In some embodiments, the synthetic polymer material comprises two different inorganic phosphor dopants (102), each inorganic phosphor dopant being a metal oxide (106) containing rare earth ions (107), and the combined emission of the two inorganic phosphor dopants (102) produces white or off-white visible light (104). For example, in some embodiments, the host material (101) of the synthetic polymer can include a first inorganic phosphor dopant of Y2SiO5:Ce(III) that emits blue visible light (104) having a wavelength of about 400 nm and a second inorganic phosphor dopant of InBO3:Eu(III) that emits yellow visible light (104) having a wavelength of about 588 nm. The combined visible light produces white or off-white visible light (104).

[0068] In some embodiments of a method for preparing a synthetic polymer composition having improved color stability, the inorganic phosphor dopant (102) contains rare earth ions (107) or transition metal ions and is a metal fluoride (109) selected from the group consisting of Cs2NaYF6, NaCeF4, NaYF4, and NaGd4. Such metal fluoride hosts often have the characteristics of a large bandgap, structural defects that are likely to act as electron traps, and anionic defects that make it useful for inorganic phosphors.

[0069] In some embodiments of a method for preparing a synthetic polymer composition having improved color stability, the synthetic polymer material comprises three different inorganic phosphor dopants (102), each inorganic phosphor dopant being a metal oxide (106) or a metal fluoride (109) containing a rare earth ion (107), and the combined emission of the three inorganic phosphor dopants (102) produces white or off-white visible light (104). In some embodiments, the synthetic polymer material comprises three different inorganic phosphor dopants (102), each inorganic phosphor dopant being a metal oxide (106) containing a rare earth ion (107), and the combined emission of the three inorganic phosphor dopants (102) produces white or off-white visible light (104). For example, in some embodiments, the host material (101) of the synthetic polymer emits blue visible light (104) having a wavelength of about 450 nm, BaMg2Al 16 O 27 :Eu(II) as the first inorganic phosphor dopant (102), Y2SiO5:Tb(III) as the second inorganic phosphor dopant (102) that emits green visible light (104) having a wavelength of about 545 nm, and Y2O3:Eu(III) as the third inorganic phosphor dopant (102) that emits red visible light (104) having a wavelength of about 611 nm. The combined visible light produces white or off-white visible light (104).

[0070] In some embodiments of a method for preparing a synthetic polymer composition having improved color stability, the host material (101) of the synthetic polymer is a thermoplastic material, the thermoplastic material is polyvinyl fluoride, the host material comprises two inorganic phosphor dopants (102), the first inorganic phosphor dopant (102) is Y2SiO5:Ce(III) that emits blue visible light (104) having a wavelength of about 400 nm, and the second inorganic phosphor dopant (102) is InBO3:Eu(III) that emits yellow visible light (104) having a wavelength of about 588 nm.

[0071] In an embodiment, the prepared synthetic polymer composition exhibits mechanical and flammability properties comparable to those of a synthetic polymer composition that does not contain one or more inorganic phosphor dopants. For example, ASTM E1354 (ASTM E-1354) is a fire test response standard that measures the response of a material to a controlled level of radiant heat and can be used to evaluate the flammability properties of a material. Other methods for analyzing the flammability properties of a material include ASTM D7309-21b and ASTM E2058-19. The mechanical properties of a material can be evaluated, for example, using a universal materials testing machine that measures tensile strength or compressive strength. In addition, a hydraulic fatigue testing machine can be used to measure the fatigue of a material.

[0072] In some embodiments of a method for preparing a synthetic polymer composition having improved color stability, contacting a host material (101) of a synthetic polymer with one or more inorganic phosphor dopants (102) to prepare an inorganic phosphor-doped synthetic polymer material can be carried out for a time sufficient to incorporate the one or more inorganic phosphor dopants (102) into the host material (101) of the synthetic polymer.

[0073] Methods for preparing solid phosphors are known in the art. See, for example, Broxtermann et al. ECS Journal of Solid State Science and Technology, 6(4) R47-R52 (2017); and Poelman et al. Journal of Applied Physics 128, 240903 (2020). In an example, a host material of metal oxide (or metal fluoride) and a rare earth oxide are weighed such that a certain amount of rare earth ions are substituted or doped into the metal oxide (or metal fluoride) lattice. The amount of ions added can be determined by calculating the stoichiometry presented for the material and then weighing out the appropriate amounts of starting materials using dimensional analysis. The metal oxide powder is thoroughly ground using a mortar and pestle to maximize the contact between the particles in the mixture. After being placed in a suitable crucible (often alumina), the mixture is heated in a tube furnace or muffle furnace to a temperature sufficient to induce a solid reaction but below the melting point of the final compound. From a temperature about 200 - 300 °C lower than this melting temperature, the particle size of the final compound increases significantly. Such a heating process is called sintering. Sintering generally results in a very dense and strongly aggregated material that cannot be directly applied as a phosphor. Therefore, in many cases, it is necessary to grind manually or using a ball mill after synthesis.

[0074] Ball milling is a mechanical method of reducing particle size by mechanical impact and friction. Typically, the powder is placed in a milling jar together with a number of hard milling balls (often Al2O3 or ZrO2) and a solvent such that a slurry is obtained. The milling jar is then moved so as to maximize the friction. Similar to the case of manual grinding using a mortar and pestle, the effectiveness of this process depends greatly on the size and hardness of the starting materials.

[0075] In the case of the above solid synthesis, the atmosphere used for heating can vary depending on the host material. In the case of oxides, air can usually be applied. However, some dopants, especially europium, are oxidized within the oxygen lattice while being heated in oxygen, leading to the formation of a fully oxidized Eu 3+ dopant. If Eu 2+ is the preferred valence state of this dopant, additional heat treatment may be required in a reducing atmosphere such as helium or argon.

[0076] Other methods for preparing the inorganic phosphor dopant (102) include sol-gel synthesis, colloidal synthesis, and coprecipitation. In the sol-gel method, for example, powders are weighed out, dissolved in a concentrated acid such as HNO3 (e.g., 70% w / w), and then diluted with deionized water. This solution can then be cooled to room temperature and added dropwise to a low-temperature saturated aqueous solution of another acid such as oxalic acid. The solid material is then precipitated and washed with deionized water and other polar solvents (such as acetone, acetonitrile, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), isopropanol, or methanol). The solid material is then calcined at a temperature of about 1000 °C to 1200 °C for several hours, followed by intermittent grinding and sintering. In some embodiments, after weighing and mixing, the metal oxide host powder and the rare earth oxide powder are directly placed into a furnace at 1000 - 1100 °C for 2 - 48 hours.

[0077] Next, the prepared solid phosphor dopant material is inserted into the synthetic polymer substrate host material. The host material of the synthetic polymer substrate can be purchased from commercial suppliers such as Dupont or Sigma. The solid phosphor material is in powder form and can be incorporated into the host material of the synthetic polymer substrate by melting the polymer substrate and then mixing it with the solid phosphor material. When two or more inorganic phosphor dopants (102) are incorporated into the host material of the synthetic polymer substrate, the powders of the two or more inorganic phosphor dopants can first be mixed and then dispersed throughout the host material of the synthetic polymer substrate. Mixing the powder throughout the host material of the substrate can be facilitated, for example, by further heating the material and / or by using a mixing paddle.

[0078] An adequate amount of the solid phosphor dopant can be incorporated into the host material (101) of the synthetic polymer to maintain the color stability of the synthetic polymer host.

[0079] After incorporating the solid phosphor dopant into the host material (101) of the synthetic polymer, the host material (101) of the inorganic phosphor-doped synthetic polymer is cured. Curing can be carried out, for example, at room temperature in air. Curing can be achieved by the inorganic phosphor dopant uniformly dispersed throughout the substrate material in the host material (101) of the inorganic phosphor-doped synthetic polymer.

[0080] Furthermore, the present disclosure includes examples according to the following clauses.

[0081] Clause 1. A method for improving the color stability of a synthetic polymer composition, comprising exposing a host material of a synthetic polymer containing one or more inorganic phosphor dopants to ultraviolet light, wherein one or more inorganic phosphor dopants in the host material of the synthetic polymer absorb the ultraviolet light and then emit it as down-converted visible light.

[0082] Clause 2. The method according to Clause 1, wherein absorption of ultraviolet light by one or more inorganic phosphor dopants reduces photooxidation of the host material of the synthetic polymer.

[0083] Clause 3. The method according to Clause 1 or 2, wherein the visible light emitted by one or more inorganic phosphor dopants creates a brighter appearance in the synthetic polymer composition.

[0084] Clause 4. The method according to any one of Clauses 1 to 3, wherein the host material of the synthetic polymer contains two or more inorganic phosphor dopants, and the down-converted visible light emitted by the two or more inorganic phosphor dopants combines to produce white or off-white light.

[0085] Clause 5. The method according to any one of Clauses 1 to 4, wherein the host material of the synthetic polymer contains three or more inorganic phosphor dopants, and the down-converted visible light emitted by the three or more inorganic phosphor dopants combines to produce white or off-white light.

[0086] Clause 6. The method according to any one of Clauses 1 to 5, wherein the ultraviolet light absorbed by one or more inorganic phosphor dopants has a wavelength between about 160 nm and 380 nm.

[0087] Clause 7. The method according to Clause 6, wherein the ultraviolet light absorbed by one or more inorganic phosphor dopants has a wavelength of about 222 nm, 254 nm, or 275 nm.

[0088] Clause 8. The method according to any one of Clauses 1 to 7, wherein the host material of the synthetic polymer is thermoplastic or thermosetting.

[0089] Clause 9. The method according to Clause 8, wherein the host material of the synthetic polymer is selected from the group consisting of tetrafluoroethylene, polyvinyl fluoride, polyurethane, polyester, epoxy, phenol, vinyl ester, polyamide, polyamide-imide, polyetherimide, polyvinyl chloride, polyether ketone ketone, polycarbonate, polyphenyl sulfone, polymethyl methacrylate, polyacrylate, and benzoxazine.

[0090] Clause 10. The method according to any one of Clauses 1 to 9, wherein the one or more inorganic phosphor dopants are metal oxides or metal fluorides containing rare earth ions selected from the group consisting of Pr3+, Ce3+, Eu3+, Eu2+, Gd3+, Tb3+, and Dy3+, or combinations thereof.

[0091] Clause 11. The method according to Clause 10, wherein the metal oxide is selected from the group consisting of silicate, phosphate, borate, oxide, oxynitride, oxysulfide, and aluminate, or combinations thereof.

[0092] Clause 12. A synthetic polymer composition comprising a host material of a synthetic polymer containing one or more inorganic phosphor dopants, wherein the one or more inorganic phosphor dopants in the host material of the synthetic polymer emit down-converted visible light upon exposure to ultraviolet light, and the synthetic polymer composition exhibits mechanical properties and flammability characteristics comparable to those of a synthetic polymer composition not containing the one or more inorganic phosphor dopants.

[0093] Clause 13. The synthetic polymer composition according to Clause 12, wherein the ultraviolet light has a wavelength between about 160 nm and 380 nm.

[0094] Clause 14: The synthetic polymer composition according to Clause 13, wherein the ultraviolet light has a wavelength of about 222 nm, 254 nm, or 275 nm.

[0095] Clause 15. The synthetic polymer composition according to any one of Clauses 12 to 14, wherein the host material of the synthetic polymer is thermoplastic or thermosetting.

[0096] Clause 16. The synthetic polymer composition according to Clause 15, wherein the host material of the synthetic polymer is selected from the group consisting of tetrafluoroethylene, polyvinyl fluoride, polyurethane, polyester, epoxy, phenol, vinyl ester, polyamide, polyamide-imide, polyetherimide, polyvinyl chloride, polyether ketone ketone, polycarbonate, polyphenyl sulfone, polymethyl methacrylate, polyacrylate, and benzoxazine.

[0097] Clause 17. The synthetic polymer composition according to any one of Clauses 12 to 16, wherein the one or more inorganic phosphor dopants are metal oxides or metal fluorides containing rare earth ions selected from the group consisting of Pr 3+ , Ce 3+ , Eu 3+ , Eu 2+ , Gd 3+ , Tb 3+ , and Dy 3+ , or combinations thereof.

[0098] Clause 18. The synthetic polymer composition according to Clause 17, wherein the metal oxide is selected from the group consisting of silicate, phosphate, borate, oxide, oxynitride, oxysulfide, and aluminate, or combinations thereof.

[0099] Clause 19. The synthetic polymer of the composition according to any one of Clauses 12 to 18, wherein the polymer composition has improved color stability compared to a coating lacking one or more inorganic phosphor dopants that have been exposed to ultraviolet light.

[0100] Clause 20. A method for preparing a synthetic polymer composition, Preparing an inorganic phosphor-doped synthetic polymer material by contacting a host material of a synthetic polymer with one or more inorganic phosphor dopants, wherein one or more inorganic phosphor dopants in the inorganic phosphor-doped synthetic polymer material can absorb ultraviolet light and then emit it as down-converted visible light, the method comprising contacting a host material of a synthetic polymer with one or more inorganic phosphor dopants.

[0101] Clause 21. The method according to clause 20, wherein the ultraviolet light absorbed by one or more inorganic phosphor dopants has a wavelength between about 160 nm and 380 nm.

[0102] Clause 22. The method according to clause 21, wherein the ultraviolet light absorbed by one or more inorganic phosphor dopants has a wavelength of about 222 nm, 254 nm, or 275 nm.

[0103] Clause 23. The method according to any one of clauses 20 to 22, wherein the host material of the synthetic polymer is thermoplastic or thermosetting.

[0104] Clause 24. The method according to clause 23, wherein the host material of the synthetic polymer is selected from the group consisting of tetrafluoroethylene, polyvinyl fluoride, polyurethane, polyester, epoxy, phenol, vinyl ester, polyamide, polyamide-imide, polyetherimide, polyvinyl chloride, polyether ketone ketone, polycarbonate, polyphenyl sulfone, polymethyl methacrylate, polyacrylate, and benzoxazine.

[0105] Clause 25. The method according to any one of clauses 20 to 24, wherein one or more inorganic phosphor dopants are metal oxides or metal fluorides containing rare earth ions selected from the group consisting of Pr3+, Ce3+, Eu3+, Eu2+, Gd3+, Tb3+, and Dy3+, or mixtures thereof.

[0106] Clause 26. The method according to clause 25, wherein the metal oxide is selected from the group consisting of silicates, phosphates, borates, oxides, oxynitrides, oxysulfides, and aluminates, or combinations thereof.

[0107] Clause 27. The method according to any one of clauses 20 to 26, wherein the prepared synthetic polymer composition exhibits mechanical and combustible properties comparable to those of a synthetic polymer composition that does not contain one or more inorganic phosphor dopants.

[0108] Clause 28. The method according to any one of clauses 20 to 27, wherein the polymer composition has improved color stability compared to a coating lacking one or more inorganic phosphor dopants that has been exposed to ultraviolet light.

[0109] The following examples are provided for illustrative purposes and are not intended to be limiting.

Examples

[0110] Preparation of a Synthetic Polymer Material with Improved Color Stability Step 1.Y 2-x SiO 5 : x Preparation of Ce phosphor powder Y(NO3)3·6H2O, Na2SiO3·9H2O, Ce(NO3)3, and NaOH for analysis are purchased from Sigma Aldrich. First, Y(NO3)3·6H2O, Na2SiO3·9H2O, Ce(NO3)3, and NaOH are added to a 100 mL glass beaker in amounts such that the final product results in a 0.75 - 2% substitution of Y sites in the Y2SiO5 lattice by cerium. After stirring for 30 minutes, the solution is poured into a 70 mL hydrothermal autoclave. The autoclave is sealed and placed in a microwave digestion system. During the reaction process, the temperature of the autoclave is maintained at 200 °C. After 20 minutes, the autoclave is removed from the microwave hydrothermal apparatus and allowed to cool naturally to room temperature. The precipitate is then filtered, washed with deionized water and isopropyl alcohol, and dried at 80 °C for 1 hour. Subsequently, the inorganic phosphor dopant (102)Y 2-x SiO5: x powders of Ce are heated at 700 °C and 900 °C respectively.

[0111] The prepared Y 2-x SiO5: x Ce inorganic phosphor dopant (102) is analyzed by powder X-ray diffraction. The crystal structure is analyzed using FullProf, and Y 2-x SiO5: x Ce is verified for the Ce / Y site mixing in the crystal structure.

[0112] Step 2.In 1-x BO 3 : x Preparation of Eu phosphor powder Indium(III) nitrate (99.9%, (In(NO3)3), tri-n-butyl borate (98%, (C 12 H 27BO3), citric acid (C6H8O7), and europium nitrate (Eu(NO3)9·5H2O) are purchased from Sigma Aldrich. First, stoichiometric amounts of indium nitrate and tri-n-butyl borate are dissolved in distilled water. Europium nitrate is added to the solution in an amount such that the final product results in a substitution of 0.75 - 2% of the In sites in the InBO3 lattice by europium. Then a sufficient amount of citric acid is added to the solution as a chelating agent. A 1:1 citric acid to total metal ion molar ratio is used. The powder is dried in an oven at 120 °C for 10 hours. Subsequently, the powder is calcined in air at 700 °C for 3 hours.

[0113] The prepared In 1-x BO3: x Eu inorganic phosphor dopant (102) is analyzed by powder X-ray diffraction. The crystal structure is analyzed using FullProf to verify the In / Eu site mixing in the InBO3 crystal structure.

[0114] Step 3.Y 2-x SiO 5 : x Ce and In 1-x BO 3 : x Preparation of Ce and In, Eu-doped polyvinyl fluoride Polyvinyl fluoride (Dupont) is heated to about 180 °C under an argon atmosphere to melt the material. The inorganic phosphor dopant (102) prepared in Steps 1 and 2, which is Y 2-x SiO5: x Ce and In 1-x BO3: x Eu phosphor powder is mixed and ground using an agate mortar and pestle. Then the mixed phosphor powder is mixed thoroughly with the melted polyvinyl fluoride such that Y 2-x SiO5: x Ce and In 1-x BO3: x Eu is uniformly dispersed throughout the polyvinyl fluoride host material. Then the doped polyvinyl fluoride is cured to solidify the Y 2-x SiO5: xCe and In 1-x BO3: x Form an Eu-doped polyvinyl fluoride substrate material.

[0115] In some embodiments, Y 2-x SiO5: x Ce and In 1-x BO3: x The Eu-doped polyvinyl fluoride substrate material can be shaped, for example, using a mold, while it cures. The mold is Y 2-x SiO5: x Ce and In 1-x BO3: x The Eu-doped polyvinyl fluoride substrate material can help to form usable products, such as covers for cabinets, counters, wallpaper, or various household, medical, automotive, or aerospace products. Additionally, the solidified Y 2-x SiO5: x Ce and In 1-x BO3: x After preparing the Eu-doped polyvinyl fluoride substrate material, the material can be easily shaped and modified, for example, using a saw, sandpaper, or a suitable mold.

[0116] Y 2-x SiO5: x Ce and In 1-x BO3: x Color stability of Eu-doped polyvinyl fluoride The Y prepared in step 3 2-x SiO5: x Ce and In 1-x BO3: x Expose the Eu-doped polyvinyl fluoride material to ultraviolet light (103) having a wavelength between about 160 nm and 380 nm, which is the radiative excitation energy of the Y 2-x SiO5: x Ce and In 1-x BO3: x Eu phosphor in the polyvinyl fluoride host substrate material. Expose the substrate material to an ultraviolet lamp for approximately 2 to 10 minutes, Y 2-x SiO5: x Ce and In 1-x BO3:x Charge the Eu phosphor. Then turn off the ultraviolet lamp. Then Y in the polyvinyl fluoride host material 2-x SiO5: x Ce and In 1-x BO3: x The Eu phosphor emits visible light (104) in the range from about 3 nanoseconds to about 15 minutes. Y 2-x SiO5: x The Ce phosphor emits blue light having a wavelength of about 400 nm, and In 1-x BO3: x The Eu phosphor emits yellow visible light (104) having a wavelength of about 588 nm. The combined visible light from the phosphor produces white visible light (104), creating a brighter appearance on the polyvinyl material.

[0117] In another embodiment, the ultraviolet light (103) can be a pulsed xenon-ultraviolet device having a wavelength of about 222 nm, 254 nm, or 275 nm, and the inorganic phosphor dopants (102) in the polyvinyl fluoride host substrate material, i.e., Y 2-x SiO5: x Ce and In 1-x BO3: x Eu phosphor) is used as an excitation source to excite.

[0118] Comparative Example: Flammability ASTM E1354 (ASTM E-1354) is a fire test response standard that measures the response of materials to a controlled level of radiant heat. This test method is commonly used to prove that products introduced into the market comply with the standards and to test new products under development for quality control purposes. ASTM E1354 uses a cone calorimeter and oxygen consumption calorimetry to determine the amount of heat released from the burning products. The heat release rate (RHR) and the amount of heat released by the products directly contribute to the severity of the fire, the spread of the flame, and the spread of the fire.

[0119] The ASTM E1354 test is performed using a cone calorimeter. The main components of the cone calorimeter are a conical furnace for generating radiant heat, a spark igniter for igniting the specimen, a load cell for measuring mass loss, and an exhaust system where smoke is measured and gas samples are taken. The gas from which the sample is extracted is passed through an oxygen analyzer to determine heat release.

[0120] In this example, a cone calorimetry test is performed on a polyvinyl fluoride host material and compared to a Y 2-x SiO5: x Ce and In 1-x BO3: x Eu-doped polyvinyl fluoride material. Briefly, the specimen is placed on top of the load cell and below the conical furnace. The spark igniter is moved over the surface of the sample until sustained combustion is achieved across the entire surface of the sample. The test can also be performed without the use of a spark igniter. The products of combustion are drawn through the exhaust system where a laser is passed through the duct to measure smoke and the gas is sampled and sent to an oxygen analyzer. The test is continued for 2 minutes after the last sign of flame is seen, or the mass loss rate drops below 150 g / m 2 or the specimen mass is completely consumed, or the oxygen concentration returns to its pre-test value, or 60 minutes have elapsed.

[0121] The ASTM E1354 report obtained from the above experimental procedure shows that both the polyvinyl fluoride host material and the Y 2-x SiO5: x Ce and In 1-x BO3: x Eu-doped polyvinyl fluoride material exhibit equivalent characteristics including time to ignition, time for the flame to die out, peak heat release rate, time to peak heat release rate, average heat release rate, total heat generated, average effective heat of combustion, average smoke extinction area, and time to peak smoke extinction area.

[0122] Supplementary Example: Blend of Phosphor and Polyacrylate Purchase polyacrylate from Alfa. Y prepared in Steps 1 and 2 above 2-x SiO5: x Ce and In 1-x BO3: x Grind and mix the Eu phosphor powder together using an agate mortar and pestle. Heat the polyacrylate to approximately 125 °C to slightly melt the material. Add the phosphor powder to the melted polyacrylate and mix for approximately 10 minutes with a mixing paddle to uniformly disperse the powder throughout the polyacrylate host material. Then cure the material in air.

[0123] Y 2-x SiO5: x Ce and In 1-x BO3: x Color stability of Eu-doped polyacrylate Y prepared above 2-x SiO5: x Ce and In 1-x BO3: x Expose the Eu polyacrylate material to ultraviolet light (103) having a wavelength between approximately 160 nm and 380 nm. This is the radiative excitation energy of the Y 2-x SiO5: x Ce and In 1-x BO3: x Eu phosphor in the substrate material. Expose the substrate material to the ultraviolet lamp for approximately 2 to 10 minutes to charge the Y 2-x SiO5: x Ce and In 1-x BO3: x Eu phosphor in the polyacrylate host material. Then turn off the ultraviolet lamp. Then the Y 2-x SiO5: x Ce and In 1-x BO3: x Eu phosphor in the polyacrylate host material emits visible light (104) in the range from approximately 3 nanoseconds to approximately 15 minutes. The Y 2-x SiO5: x Ce phosphor emits blue light having a wavelength of approximately 400 nm, and the In 1-x BO3: xThe Eu phosphor emits yellow light with a wavelength of approximately 588 nm. The combined visible light from the phosphor produces white light, creating a brighter appearance on the polyacrylate material.

[0124] Efforts have been made to ensure accuracy regarding the numerical values (amounts, temperatures, etc.) used, but some experimental errors and deviations should be taken into account.

[0125] Those skilled in the art will recognize many methods and materials similar or equivalent to those described herein that can be used in practicing the subject matter described herein. This disclosure is not limited to the methods and materials described in any sense.

[0126] Where a range of values is specified, unless the context clearly indicates otherwise, each intervening value between the upper and lower limits of that range to one-tenth of the unit of the lower limit, as well as other recited values or intervening values within the recited range, is to be understood as being included. The upper and lower limits of these smaller ranges that can be independently included within the smaller ranges are also included, subject to the particular upper and lower limits excluded within the recited range. Where one or both of the upper and lower limits of the recited range are included, ranges excluding one or both of them are also included.

[0127] Those skilled in the art related to the subject matter, benefiting from the teachings presented in the foregoing description and the accompanying drawings, will envision numerous modifications and other embodiments of the present disclosure. Accordingly, the present subject matter is not to be limited to the specific embodiments disclosed, and it is intended that modifications and other embodiments be included within the scope of the claims. Specific terms are used herein, but they are used only in a general and illustrative sense and not for purposes of limitation.

Claims

1. A method for improving the color stability of a synthetic polymer composition, This includes exposing a host material of a synthetic polymer containing one or more inorganic phosphor dopants to ultraviolet light. The one or more inorganic phosphor dopants in the host material of the synthetic polymer absorb the ultraviolet light and then emit the ultraviolet light as down-converted visible light. method.

2. The method according to claim 1, wherein the absorption of ultraviolet light by the one or more inorganic phosphor dopants reduces the photo-oxidation of the host material of the synthetic polymer.

3. The method according to claim 1 or 2, wherein the visible light emitted by the one or more inorganic phosphor dopants produces a brighter appearance for the synthetic polymer composition.

4. The method according to claim 1, wherein the host material of the synthetic polymer comprises two or more inorganic phosphor dopants, and the downconverted visible light emitted by the two or more inorganic phosphor dopants is combined to produce white or off-white light, and / or the host material of the synthetic polymer comprises three or more inorganic phosphor dopants, and the downconverted visible light emitted by the three or more inorganic phosphor dopants is combined to produce white or off-white light.

5. The method according to claim 1, wherein the ultraviolet light absorbed by the one or more inorganic phosphor dopants has wavelengths between approximately 160 nm and 380 nm.

6. The method according to claim 1, wherein the host material of the synthetic polymer is thermoplastic or thermosetting.

7. The aforementioned one or more inorganic phosphor dopants, ３＋ Ce ３＋ , Eu ３＋ , Eu ２＋ , Gd ３＋ , Tb ３＋ , and Dy ３＋ The method according to claim 1, wherein the metal oxide or metal fluoride is a rare earth ion selected from the group consisting of, or a combination thereof.

8. A synthetic polymer composition, A host material for a synthetic polymer comprising one or more inorganic phosphor dopants, wherein the one or more inorganic phosphor dopants in the host material of the synthetic polymer emit visible light that is downconverted upon exposure to ultraviolet light. The synthetic polymer composition exhibits mechanical properties and flammability comparable to those of a synthetic polymer composition that does not contain the one or more inorganic phosphor dopants. Synthetic polymer composition.

9. The synthetic polymer composition according to claim 8, wherein the host material of the synthetic polymer is thermoplastic or thermosetting.

10. The one or more inorganic phosphor dopants are Pr ３＋ , Ce ３＋ , Eu ３＋ , Eu ２＋ , Gd ３＋ , Tb ３＋ , and Dy ３＋ The synthetic polymer composition according to claim 8 or 9, which is a metal oxide or metal fluoride containing rare earth ions selected from the group consisting of or combinations thereof.

11. A method for preparing a synthetic polymer composition, The present invention relates to preparing an inorganic phosphor-doped synthetic polymer material by contacting a synthetic polymer host material with one or more inorganic phosphor dopants, wherein the one or more inorganic phosphor dopants in the inorganic phosphor-doped synthetic polymer material are capable of absorbing ultraviolet light and subsequently emitting the ultraviolet light as down-converted visible light. A method that includes this.

12. The method according to claim 11, wherein the host material of the synthetic polymer is thermoplastic or thermosetting.

13. The aforementioned one or more inorganic phosphor dopants, ３＋ Ce ３＋ , Eu ３＋ , Eu ２＋ , Gd ３＋ , Tb ３＋ , and Dy ３＋ The method according to claim 11 or 12, wherein the metal oxide or metal fluoride is a rare earth ion selected from the group consisting of, or combinations thereof.

14. The method according to claim 11, wherein the prepared synthetic polymer composition exhibits mechanical properties and flammability comparable to those of a synthetic polymer composition that does not contain one or more inorganic phosphor dopants.

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