Patent Application
20140124715
The present invention relates to optical power-limiting devices, and more particularly, to an optical power-limiting passive device and to a method for limiting optical power transmission in lenses and windows, using absorption changes in a novel photochromic composition, having response to infrared light in addition to the conventional response to ultraviolet light.
Photochromic materials are known and exhibit a change in light transmission or color in response to actinic radiation in the spectrum of sunlight. Removal of the incident radiation causes these materials to revert back to their original transmissive state.
Such photochromic materials have applications such as sunglasses, graphics, ophthalmic lenses, solar control window films, security and authenticity labels, and many others. The use of photochromic materials, however, has been very limited due to (a) degradation of the photochromic property of the materials due to continued exposure, absorption and heating of UV light, particularly short wavelength (<400 nanometers nm), (b) the long rise and decay times of the darkening (up to minutes), (c) the lack of photochromic reaction in the absence of UV radiation, e.g., the inability to use photochromic glasses behind the front window of a car.
Ophthalmic lenses made of mineral glass are well known. Photochromic pigments have good compatibility with mineral glass. However, photochromic mineral glass lenses are heavy and have a slow photochromic reaction time, particularly in the change from dark to transparent.
Today, most spectacle lenses are made of a variety of plastics or plastic-glass composites. Most used plastics include PMMA (e.g., Plexiglas by Rohm and Haas, Perspex, Lucite, Altuglas and Optiks by Plaskolite,) and polycarbonate (e.g., Lexan by General Electric, MERLON by Mobay Chemical Company, MAKROLON by Bayer, and PANLITE from Teijin Chemical Limited).
Some success in rendering plastic ophthalmic lenses photochromic involved embedding a solid layer of photochromic mineral glass within the bulk of an organic lens material. Examples include U.S. Pat. No. 5,232,637 (Dasher, et al.) that teaches a method of producing a glass-plastic laminated ophthalmic lens structure, and U.S. Pat. No. 4,300,821 (Mignen et al.) that teaches an ophthalmic lens made of organic material having at least one layer of photochromic mineral glass within its mass to impart photochromic properties to the lens.
All known photochromic materials exhibit a change in light transmission or color in response to actinic radiation, mainly due to the UV light in the spectrum of sunlight. There are many circumstances where no UV light exists, e.g., behind windows that absorb the UV. Most of the glasses and ophthalmic polymers are transparent in the visible and near-IR ranges. One embodiment of this invention uses the penetrating near-IR light by up-converting it to the UV and short visible wavelengths and applying the UV to the photochromic material, thus producing a change in light transmission and/or color in response to IR radiation in the spectrum of sunlight or other light sources. Removal of the incident IR radiation causes these materials to revert back to their original transmissive state.
Upconversion (UC) refers to nonlinear optical processes characterized by the successive absorption of two or more pump photons via intermediate long-lived energy states followed by the emission of the output radiation at a shorter wavelength than the pump wavelength. This general concept was first recognized and formulated independently by Auzel, Ovsyankin, and Feofilov in the mid-1960s. (See, e.g., F. Auzel, Chem. Rev., 2004, 104, 139.) Since then, conversion of infrared radiation into the visible range has generated much of the interest in UC research. The knowledge gained thus far has allowed the development of effective optical devices such as infrared quantum counter detectors, temperature sensors, and compact solid state lasers.
Despite the remarkable potential utility of UC materials, the practical uses of UC materials have been extremely limited. The limitations are largely attributed to the difficulties in preparing small nano-crystals (sub-50 nm, much smaller than the visible light wavelength) that exhibit strong UC. This limitation no longer exists today, and efficient UC materials can be incorporated in photochromic devices.
Nanoscale manipulation, e.g., of lanthanide-doped UC nano-crystals, leads to important modification of their optical properties in excited-state dynamics, emission profiles and UC efficiency. For example, the reduction in particle size provides the ability to modify the lifetime of intermediate states. The control of spatial confinement of dopant ions within a nano-scopic region can lead to marked enhancement of a particular wavelength emission as well as generation of new types of emissions. (See e.g. J. W. Stouwdam and F. C. J. M. van Veggel, Nano Lett., 2002, 2, 733).
In many applications there is insufficient UV and short wave visible light radiation to actuate the photochromic material. The addition of UC materials enables the in-situ generation of UV and/or short wave visible light that in turn can trigger photochromic materials and devices in these applications. This additional response features enable the use of the photochromic composition in places where ultraviolet (UV) light and short-wave visible light is absent, or obscured, e.g., using photochromic glasses behind the front window of a car.
The present disclosure further concerns, but is not limited to, the production of windows, lenses, contact lenses, microlenses, mirrors and other optical articles. The present disclosure further relates to protecting dedicated optical elements against sun blinding, flash blinding, flash dazzling, flashing lights originating from explosions in battle fields, welding light, fire related blinding, and lenses for cameras that look directly at the sun or missile launching, and other bright emitting sources that contain visible light and infrared (IR) radiation in their spectrum.
The present disclosure further concerns uses of the limiter for power regulation in networks, in the input or at the output from components. Further uses are in the areas of medical, military and industrial lasers where an optical power limiter may be used for surge protection and safety applications.
One embodiment uses a matrix, a photochromic dye and light up-converting nanoparticle additives to provide a photochromic composition that reacts (tints) with or without application of UV or short wave visible light. In this composition, the up-converting nanoparticles absorb low energy photons, e.g., visible light and near-IR light, which is re-emitted into the system as UV or short wave visible light. The re-emitted UV light activates the photochromic material in the composition, even if no UV is arriving from an outside source.
Another embodiment provides a composition of a matrix, a photochromic dye, light up-converting nanoparticle additives, and fluorescence enhancer materials and structures, that enhance fluorescent emission from the up-converting nanoparticle additives. The enhancement of fluorescence from the up-converting nanoparticles is achieved through plasmonic coupling, also known as hot-spots or local field effect.
A further embodiment provides a composition of a matrix, a photochromic dye, light up-converting nanoparticle additives, fluorescence enhancer materials and structures, and environmental stabilizers.
The matrix in the photochromic compositions can be organic-based, e.g., a polymer film, a polymerizable composition, or a transparent adhesive, or inorganic-based, e.g., mineral glass, sol-gel, and any other window based material, and an inorganic-organic composite.
Specific embodiments utilize various UC nanoparticles in the photochromic compositions, such as LaF3, NaYF4, LuPO4, YbPO4, GdOF, La2(MoO4)3, YVO4, ZrO2, TiO2, BaTiO3, Lu3Ga5O12, Gd2O3 or La2O2S, where the doping ions include lanthanides such as Yb, Er, Tm, Eu, Nd or Ho.
Various photochromic materials that can be used in the photochromic compositions include, but are not limited to, organic and inorganic photochromics and mixtures thereof. Organic photochromic dyes can be pyrans, oxazines, fulgides, fulgimides, diarylethenes and mixtures thereof. These may be a single photochromic compound, a mixture of photochromic compounds, a material comprising a photochromic compound, such as a monomeric or polymeric ungelled solution; and a material such as a monomer or polymer to which a photochromic compound is chemically bonded. Inorganic photochromics can be crystallites of silver halides, cadmium halide and/or copper halide.
Various fluorescence enhancing materials can be used in the photochromic compositions to enhance fluorescence emission from the up-converting nanoparticles. The enhancement of fluorescence from the up-converting nanoparticles is achieved through plasmonic coupling, also known as hot-spots or local field effect. Examples include, but are not limited to, metallic plasmonic nanostructures such as spiked nanoparticles, hollow-shell nanoparticles, rice-like nanoparticles, nonconcentric-nanoshell nanoparticles, crescent-moon-structured nanoparticles, nanoshells composed of a dielectric core with alternating layers of metal, dielectric, and metal “nanomatryushka,” (e.g., concentric nanoshells).
Various stabilizers that can be used in the photochromic compositions include hindered amine light stabilizer (HALS), UV absorbers, thermal stabilizers, singlet oxygen quenchers, and various antioxidants. The various stabilizers generally inhibit radiation-induced degradation reactions from occurring in polymeric materials, and thereby extend the useful life of the matrix material hosting the photochromic and up-converting materials.
Various thermal conductivity enhancers used to enhance the thermal conductivity of the matrix used for the photochromic compositions effectively achieve two purposes. One, heat that builds up in the optical element during the absorption of light can dissipate more easily to other elements in the system, effectively reducing the thermal degradation of both the matrix and the photochromic dye. Second, since most photochromic dyes are converted from their colored form (tinted form) to colorless form by the absorption of visible light and by heat, removing the heat element will change the equilibrium of colored and colorless molecules.
In one specific embodiment, the thermal conductivity of polymeric matrixes is achieved by the addition of nanoparticles, nanorods, nanowires, hollow nanoparticles, core-shell nanoparticles, spiked particles, and nanoparticles with various shapes. These may include nanoparticles of metal, metal oxide, metal nitrides, metal carbides, metal sulfides, and carbon-based nanomaterials, such as nanodiamond, diamond-like carbon (DLC), single-wall carbon nanotubes, double-wall carbon nanotubes, multiwall carbon nanotubes, and their functionalized forms, graphene, and carbon steel. The various compositions can be polymerized, cured or fabricated in the form of nanoparticles and/or microparticles. The nanoparticles and/or the microparticles can be further dispersed in a new matrix, appropriate for forming a window, a lens, glasses, a contact lens, a filter, a microlens array or mirrors.
Various nanoparticles and/or microparticles of the photochromic compositions can be further coated or encapsulated with a coating. The coating can serve a number of functions, such as protection of the core composition from oxidation or any form of degradation, blocking out harmful radiation, and changing the chemical nature of the particles (hydrophobic/hydrophilic) and hence the dispersability of the nanoparticles and/or microparticles. The coating can further be a UV-reflecting layer or multilayer that effectively traps the UV light emitted from the up-converting nanoparticles, effectively enhancing the absorption of the photochromic dye inside the nanoparticles and/or microparticles. The coating can be organic, inorganic or a composite, and in the form of a monolayer, a multilayer or a porous layer.
The invention will now be described in connection with certain preferred embodiments with reference to the following illustrative figures so that it may be more fully understood. With specific reference now to the figures in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention.
Thus, as described herein, optical devices, such as, for example, lenses, can be prepared to allow for a photochromic response in response to light exposure from light that is typically unable to generate a photochromic response from a photochromic dye material. Typically, photochromic materials exposed to light having an insufficiently low energy level (i.e., wavelengths not low enough), do not actuate. For example, photochromic materials actuated in response to UV or short wave visible light typically remain un-actuated (e.g., transparent) while exposed to near-IR light. However, by incorporating up-converting nano-materials in addition to photochromic dyes, light at relatively low wavelengths that does not, by itself, generate a photochromic response in photochromic materials, is absorbed by the up-converting nano-materials, and light at higher energy levels is re-emitted from the up-converting nano-materials. The re-emitted light has a sufficiently high energy level to actuate a photochromic response from the photochromic dye material. The up-converting nano-materials and/or photochromic dyes can be incorporated in an optical device as a layer applied to an optical device, as a layer of the optical device, or as a bulk material within the optical device, or as some combination of these. Accordingly, photochromic responses are now possible in areas not exposed to significant amounts of UV or short wave visible light. For example, photochromic optical corrective lenses configured to darken in response to UV light can be actuated within an interior of a vehicle having windows coated and/or treated to prevent UV light from entering the passenger portion of the vehicle.
Furthermore, the fluorescent effect of the up-converting nano-materials can be further enhanced by including fluorescence enhancers, and the response time can be decreased, such that the photochromic actuation occurs faster, by including thermal conductivity enhancers.
For exemplary purposes, several examples of combinations used to prepare photochromic materials, such as, for example, optical devices, according to the present disclosure are summarized next. In some embodiments where the prepared material including a matrix, and a photochromic dye and up-converting nanoparticles added to the matrix, the amount of photochromic dye can be selected to be 0.5% to 10% of the weight (“mass”) of the matrix; and the amount of the up-converting nanoparticles can be selected to be 0.5% to 10% of the weight of the matrix.
In some embodiments where the prepared material including a matrix, a photochromic dye, up-converting nanoparticles, and fluorescence enhancer materials and/or structures added to the matrix, the amount of photochromic dye can be selected to be 0.5% to 10% of the weight (“mass”) of the matrix; the amount of the up-converting nanoparticles can be selected to be 0.5% to 10% of the weight of the matrix; and the amount of the fluorescence enhancer materials and/or structures can be selected to be 0.5% to 5% of the weight of the matrix.
In some embodiments where the prepared material including a matrix, a photochromic dye, up-converting nanoparticles, fluorescence enhancer materials and/or structures, and environmental stabilizers added to the matrix, the amount of photochromic dye can be selected to be 0.5% to 10% of the weight (“mass”) of the matrix; the amount of the up-converting nanoparticles can be selected to be 0.5% to 10% of the weight of the matrix; the amount of the fluorescence enhancer materials and/or structures can be selected to be 0.5% to 5% of the weight of the matrix; and the amount of the environmental stabilizers can be selected to be 0.1% to 2-5% of the weight of the matrix, according to the stabilizer.
In some embodiments where the prepared material including a matrix, a photochromic dye, up-converting nanoparticles, fluorescence enhancer materials and/or structures, environmental stabilizers, and thermal conductivity enhancers added to the matrix, the amount of photochromic dye can be selected to be 0.5% to 10% of the weight (“mass”) of the matrix; the amount of the up-converting nanoparticles can be selected to be 0.5% to 10% of the weight of the matrix; the amount of the fluorescence enhancer materials and/or structures can be selected to be 0.5% to 5% of the weight of the matrix; the amount of the environmental stabilizers can be selected to be 0.1% to 2-5% of the weight of the matrix, according to the stabilizer; and the amount of the thermal conductivity enhancers can be selected to be from 0.1% to 20% of the weight of the matrix.
As used herein, near infrared (“near-IR”) generally refers to radiation in the near infrared spectrum range of the electromagnetic spectrum, e.g., radiation having wavelengths between approximately 750 nm to approximately 2500 nm. Visible light generally refers to radiation in the visible range of the electromagnetic spectrum, e.g., radiation having wavelengths between approximately 390 nm to approximately 750 nm. Short wave visible light generally refers to radiation within the visible range, or nearly within the visible range, and having wavelengths closer to the smallest wavelengths of the visible range than the longest wavelengths of the visible range, i.e., radiation having wavelengths closer to 390 nm than to 750 nm. Short wave visible light can also refer to radiation that is within the visible range or nearly within the visible range and that has wavelengths below an approximate wavelength defining the range, such as below approximately 500 nm, or below approximately 450 nm, for example. Ultraviolet (“UV”) generally refers to radiation in the ultraviolet range of the electromagnetic spectrum, e.g., radiation having wavelengths between approximately 10 nm and approximately 400 nm. Generally, both UV light and short wave visible light refers to radiation having a wavelength sufficient to actuate a photochromic material and thereby change the transparency of the photochromic material.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrated embodiments and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
This application is a U.S. national phase of and claims priority to International Application No. PCT/IB2012/050250, filed Jan. 18, 2012, which claims the benefit of priority to U.S. Provisional Patent Application No. 61/424,024, filed Jan. 19, 2011, each of which is incorporated by reference in its entirety.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/IB12/50250 | 1/18/2012 | WO | 00 | 1/21/2014 |
| Number | Date | Country | |
|---|---|---|---|
| 61434024 | Jan 2011 | US |
