Patent Application
20080084592
The present invention relates to molded articles having a shape determined by the function of the article. In general, the molded article may be anything that is made from a moldable polymeric material (for example polycarbonate, polyester, etc) where it is desirable to provide confirmation of the authenticity of the article. By way of non-limiting example, such molded articles may be housings for communications devices such as radios, cellular telephones and the like, housings for electronic equipment such as test devices, music players and recorders, and the like. Authentication can also be extended to media discs themselves (for example CDs DVDs etc), frames for eyewear (such as sunglasses), and plastic components used in brand/logo tags, or more covertly as zippers or clasps on items such as purses or shoes.
The article of the present invention is at least partially formed from or at least partially coated with a holographic recording medium in which a volume hologram can be formed.
One type of suitable holographic recording medium for use in the present invention are dye-doped thermoplastic holographic materials. Materials of this type are described in commonly assigned US Patent Publications US 2005/0136333, 2006/0078802 and 20060073392, all of which are incorporated herein by reference, for use in the storage of digital data.
In some embodiments, the holographic recording medium comprises a substrate and a dye material possessing narrowband optical properties selected and utilized on the basis of several important characteristics including the ability to change the refractive index of the dye material upon exposure to light; the efficiency with which the light creates the change; and the separation between the maximum absorption of the dye and the desired wavelength or wavelengths to be used for writing and/or reading the image. The substrate utilized in the holographic storage media of this embodiment can comprise any material having sufficient optical quality, e.g., low scatter, low birefringence, and negligible losses at the wavelengths of interest, to render the data in the holographic storage material readable. Generally, any plastic that exhibits these properties can he employed as the substrate. However, the plastic should be capable of withstanding the processing parameters (e.g., inclusion of the dye and application of any coating or subsequent layers, and molding into final format) and subsequent storage conditions. Possible plastics include thermoplastics with glass transition temperatures of about 100 C or greater, with about 150 C or greater preferred. In some embodiments, the plastic materials have glass transition temperatures greater than about 200 C, such as polyetherimides, polyimides, combinations comprising at least one of the foregoing plastics, and others. Some possible examples of these plastic materials include, but are not limited to, amorphous and semi-crystalline thermoplastic materials and blends such as: polycarbonates, polyetherimides, polyvinyl chloride, polyolefins (including, but not limited to, linear and cyclic polyolefins and including polyethylene, chlorinated polyethylene, polypropylene, and the like), polyesters, polyamides, polysulfones (including, but not limited to, hydrogenated polysulfones, and the like), polyimides, polyether sulfones, ABS resins, polystyrenes (including, but not limited to, hydrogenated polystyrenes, syndiotactic and atactic polystyrenes, polycyclohexyl ethylene, styrene-co-acrylonitrile, styrene-co-maleic anhydride, and the like), polybutadiene, polyacrylates (including, but not limited to, polymethylmethacrylate (PMMA), methyl methacrylate-polyimide copolymers, and the like), polyacrylonitrile, polyacetals, polyphenylene ethers (including, but not limited to, those derived from 2,6-dimethylphenol and copolymers with 2,3,6-trimethylphenol, and the like), ethylene-vinyl acetate copolymers, polyvinyl acetate, ethylene-tetrafluoroethylene copolymer, aromatic polyesters, polyvinyl fluoride, polyvinylidene fluoride, and polyvinylidene chloride.
The dye materials utilized in this embodiment of the invention are suitably organic dyes which undergo an irreversible chemical change upon exposure to certain “write” wavelengths of light which eliminates the absorption band exhibited by the dye. The photoproduct or photoproducts which result from interaction of the photochemically active narrowband dye with light having the “write” wavelength typically exhibits an absorption spectrum (spectra) which is entirely different from that exhibited by the dye prior to irradiation. The irreversible chemical change in the dye produced by interaction with light of the write wavelength produces a corresponding change in the molecular structure of the dye, thereby producing a “photoproduct” which may be a cleavage-type photoproduct or a rearrangement type photoproduct. This modification to the structure of the dye molecule and concurrent changes in the light absorption properties of the photoproduct(s) relative to the starting narrowband dye produces a significant change in refractive index within the substrate that can be observed at a separate “read” wavelength. The narrowband dye materials utilized according to the present disclosure also tend to have strong optical characteristics due to conservation of oscillator strength, i.e., because the absorption is localized to a narrow spectral region, the magnitude of the absorption is stronger as the area under the curve (the oscillator strength) is conserved. Specific examples of such dyes are nitrostilbene and nitrostilbene derivative such as 4-dimethylamino-2′,4′-dinitrostilbene, 4-dimethylamino-4′-cyano-2′-nitrostilbene, 4-hydroxy-2′,4′-dinitrostilben-e, and 4-methoxy-2′,4′-dinitrostilbene. These dyes have been synthesized and optically induced rearrangements of such dyes have been studied in the context of the chemistry of the reactants and products as well as their activation energy and entropy factors. J. S. Splitter and M. Calvin, “The Photochemical Behavior of Some o-Nitrostilbenes,” J. Org. Chem., vol. 20, pg. 1086(1955). More recent work has focused on using the refractive index modulation that arises from these optically induced changes to write waveguides into polymers doped with the dyes. McCulloch, I. A., “Novel Photoactive Nonlinear Optical Polymers for Use in Optical Waveguides,” Macromolecules, vol. 27, pg. 1697 (1994).
The holographic record composition may also be a mixture of a photoactive material, a photosensitizer and a moldable or coatable organic binder material, wherein the photoactive material undergoes a change in color upon reaction with the photosensitizer.
Suitable materials for use as the photosensitive materials in such mixtures include without limitation anthraquinones and their derivatives; croconines and their derivatives; monoazos, disazos, trisazos and their derivatives; benzimidazolones and their derivatives; diketo pyrrole pyrroles and their derivatives; dioxazines and their derivatives; diarylides and their derivatives; indanthrones and their derivatives; isoindolines and their derivatives; isoindolinones and their derivatives; naphtols and their derivatives; perinones and their derivatives; perylenes and their derivatives; ansanthrones and their derivatives; dibenzpyrenequinones and their derivatives; pyranthrones and their derivatives; bioranthorones and their derivatives; isobioranthorone and their derivatives; diphenylmethane, and triphenylmethane type pigments; cyanine and azomethine type pigments; indigoid type pigments; bisbenzoimidazole type pigments; azulenium salts; pyrylium salts; thiapyrylium salts; benzopyrylium salts; phthalocyanines and their derivatives, pryanthrones and their derivatives; quinacidones and their derivatives; quinophthalones and their derivatives; squaraines and their derivatives; squarilyiums and their derivatives; leuco dyes and their derivatives, deuterated leuco dyes and their derivatives; leuco-azine dyes; acridines; di-and tri-arylmethane, dyes; quinoneamines; o-nitro-substituted arylidene dyes, aryl nitrone dyes, and combinations of such materials.
The photsensitizer is suitably a photoactivatable oxidant, a one photon photosensitizer, a two photon photosensitizer, a three photon photosensitizer, a multiphoton photosensitizer, an acidic photosensitizer, a basic photosensitizer, a salt, a dye, a free radical photosensitizer, a cationic photosensitizer, or a combination comprising at least one of the foregoing photo sensitizers. By way of non-limiting example, the photsensitizer may be a hexaarylbiimidazole compound, a semiconductor nanoparticle, a halogenated compound having a bond dissociation energy effective to produce a first halogen as a free radical of not less than about 40 kilocalories per mole, a sulfonyl halide, R—SO2—X wherein R is a member of the group consisting of alkyl, alkenyl, cycloalkyl, aryl, alkaryl, and aralkyl and X is chlorine or bromine, a sulfenyl halide of the formula R′—S—X′ wherein R′ and X′ have the same meaning as R and X, a tetraaryl hydrazine, a benzothiazolyl disulfide, a polymethacrylaldehyde, an alkylidene 2,5-cyclohexadien-1-one, an azobenzyl, a nitroso, alkyl (T1), a peroxide, a haloamine, or a combination comprising at least one of the foregoing photosensitizer. The photosensitizer may also be an acetophenone, a benzophenone, an aryl glyoxalate, an acylphosphine oxide, a benzoin ether, a benzil ketal, a thioxanthone, a chloroalkyltriazine, a bisimidazole, a triacylimidazole, a pyrylium compound, a sulfonium salt, an iodonium salt, a mercapto compond, a quinone, an azo compound, an organic peroxide or a combination comprising at least one of the foregoing photosensitizers.
The organic binder is suitably a thermoplastic polymer, a thermosetting polymer, or a combination of a thermoplastic polymer with a thermosetting polymer. For example, the organic binder material may comprise a polyacrylate, a polymethacrylate, a polyester, a polyolefin, a polycarbonate, a polystyrene, a polyamideimide, a polyarylate, a polyarylsulfone, a polyethersulfone, a polyphenylene sulfide, a polysulfone, a polyimide, a polyetherimide, a polyetherketone, a polyether etherketone, a polyether ketone ketone, a polysiloxane, a polyurethane, a polyether, a polyether amide, or a polyether ester, or a combination thereof. The organic binder may also comprise a thermosetting polymer such as an epoxy, a phenolic, a polysiloxane, a polyester, a polyurethane, a polyamide, a polyacrylate, a polymethacrylate, or a combination comprising at least one of the foregoing thermosetting polymers. The holographic recording medium may also be a combination of a photochromic compound and a moldable or curable hinder material as described above. Non-limiting examples of photochromic dyes are a diarylethene, a nitrone or a combination thereof. Specific diarylethene include without limitation diarylperfluorocyclopentenes, diarylmaleic anhydrides, diarylmaleimides Specific nitrones include, without limitation, α-(4-diethylaminophenyl)-N-phenylnitrone; α-(4-diethylaminophenyl)-N-(4-chlorophenyl)-nitrone, α-(4-diethylaminophenyl)-N-(3,4-dichlorophenyl)-nitrone, α-(4-diethylaminophenyl)-N-(4-carbethoxyphenyl)-nitrone, α-(4-diethylaminophenyl)-N-(4-acetylphenyl)-nitrone, α-(4-dimethylaminophenyl)-N-(4-cyanophenyl)-nitrone, α-(4-methoxyphenyl)-N-(4-cyanophenyl)nitrone, α-(9-julolidinyl)-N-phenylnitrone, α-(9-julolidinyl)-N-(4-chlorophenyl)nitrone, α-[2-(1,1-diphenylethenyl)]-N-phenylnitrone, α-[2-(1-phenylpropenyl)]-N-phenylnitrone, or the like, or a combination comprising at least one of the foregoing nitrones.
In the molded articles of the invention, a volume hologram is formed in the holographic recording medium. This volume hologram displays an image that is directly interpretable by the human eye when interrogated with an effective interrogating beam. As used herein, the phrase “directly interpretable by the human eye” indicates that the hologram has the form of an image such as a picture or alphanumeric text or other grouping or readily distinguished symbols, as opposed to a presentation of data which cannot be realistically interpreted without the aid of a reading machine/computer. The phrase “interrogated with an effective interrogating beam” refers to applying a laser beam of appropriate wavelength based upon the wavelength used in the recording of the hologram, and with a beam of appropriate phase when the image is phase-encoded, at an angle that results in the display of an image.
Depending on the application, it may be desirable to have the holographic image invisible to the naked eye or visible to the naked eye, or to the image provide a combination of both visible and invisible components. This is generally controlled by way of the material thickness. The Bragg detuning curve (see the equations in
The hologram thickness can be controlled via a number of methods.
When the hologram is invisible, the image will only he properly displayed when the hologram is interrogated with an appropriate beam, that matches the reference beam in wavelength, incidence angle and phase alterations, if any. To facilitate the reading of the hologram without expensive additional equipment, it is desirable to match the wavelength of the reference beam to commonly available handheld laser pointers, such as HeNe red laser pointers. In addition, it is desirable to record the hologram in a manner that maximizes the angular tolerance for display so that no special alignment tools need to be used. As described above, this is achieved by controlling the thickness of the hologram. To facilitate use of a handheld laser pointer, it is desirable to hive an angular tolerance (the angle by which the incidence angle can depart from the actual recording angle and still result in an image) of at least 0.5 degrees. As indicated in
The specific content of the hologram imparted in the molded article of the present invention depends on the needs of the user, with the proviso that in the articles of the invention this content always includes an image that is directly interpretable by the human eye when properly interrogated to display an image. In addition to this image, the hologram may also include digital data, or a multiplicity of images.
As depicted in
In
The present invention further provides a method for making a molded article incorporating a volume hologram, The method comprises the steps of: (a) molding an article from a hologtraphic recording medium, and (b) writing a volume hologram in the molded article, wherein the volume hologram displays an image that is directly interpretable by the human eye when interrogated with an effective interrogating beam. The molding of the article may be performed by any of the numerous molding methods known in the art, including without limitation injection molding,
The present invention also provides a method for making a molded article incorporating a volume hologram, comprising the steps of: (a) molding an article from a thermoplastic material; (b) coating the molded article in a hologtraphic recording medium, and (c) writing a volume hologram in the coating of holographic recording medium, wherein the volume hologram displays an image that is directly interpretable by the human eye when interrogated with an effective interrogating beam. The cloating process can be by any method, including for example spray coating and dip coating provided it provides a reproducible coating thickness onto the base molded article.
As an example of the present invention a 120 mm diameter, 1.2 mm thick disc 60 with optical quality front and back surfaces was injection molded from a holographic recording material. The material was an optical quality polystyrene containing about 1 weight % of the extended-CEM-388 nitrone dye shown below:
The disc 60 was placed at the sample location of the recording system shown in
The signal and reference beams were incident into the disc 60 with an angle of 45 degrees with respect to the disc. The power level of the light was adjusted such that both the signal and reference beams had 14 mW of power. The shutter 63 was then opened to expose the disc to the recording light for 12 to 15 seconds. For evaluation a red HeNe laser 69 producing 1-3 mW of laser light at 633 nm was used to measure the efficiency of the recorded hologram. Under the described recording conditions, holograms of 12% to 15% diffraction efficiency were achieved. The location of the hologram was then indicated on the disc and the disc was removed from the recording system.
For read out of the logo hologram a second system was used. The read out or authentication system is shown in
