Abstract: The invention provides (1) a volume hologram transfer foil comprising a substrate and protective layer, a volume hologram layer and a heat seal layer stacked on the substrate in this order, wherein a multilayer structure comprising the protective layer, the volume hologram layer and the heat seal layer in this order is releasable from the substrate, and (2) a volume hologram transfer foil wherein the above protective layer is used as a heat seal layer. The heat seal layer comprises a polyester resin having a glass transition temperature of ?10° C. to ?30° C. With the invention, thermo-compression adhesion of the volume hologram layer to any application member, especially a polyester resin card is improved, so that the invention provides a volume hologram transfer foil useful for prevention of illegal copying, and a volume hologram multilayer structure formed using such a transfer foil.

Abstract: A laminated holographic recording medium having (a) a first substrate having a through-hole and (b) a solid polymer matrix layer that records holographic data laminated to the first substrate and a method of manufacturing thereof are disclosed. The method of manufacturing preferably requires injecting a precursor material through the through-hole and polymerizing the precursor material in contact with the first substrate to form the polymer matrix layer.

Abstract: A multilayer holographic film includes a first layer and an embossed layer on at least one side of the first layer and having a micro-embossed holographic image therein. The embossed layer is thinner than the first layer and has a lower embossing temperature than the first layer. The hologram-receiving layer with a micro-embossed holographic image embossed therein is adapted to receive a metal layer thereon, if desired, and the layer includes a cycloolefin copolymer as the primary polymer component.

Abstract: A method of making a holographic device (4) comprises the steps of: forming a heterogeneous support medium (2) having at least two regions (1) which are heterogeneous; placing the heterogeneous support medium under recording conditions, e.g. in a liquid X, which are selected to change one or more physical properties of the heterogeneous support medium, wherein the extent or nature of the change in the physical property or physical properties is different in at least two of the heterogeneous regions; recording a holographic image in the heterogeneous support medium while it is under recording conditions; and removing the heterogeneous support medium from recording conditions. Such a device can be used for security and authentication.

Abstract: A hologram recording film manufacturing method includes the steps of obtaining a laminated structure by alternately laminating M (where M?2) photosensitive material precursor layers including a photosensitive material and at least one (M?1) resin layer on one another, obtaining M photosensitive material layers, where at least two interference fringes with a desired pitch and a desired slant angle are formed on each of the M photosensitive material layers, from the M photosensitive material precursor layers by irradiating the laminated structure with a reference laser light beam and an object laser light beam, and making the slant angles of the M photosensitive material layers different from each other while retaining the pitch value, which is defined on a face of the photosensitive material layer, by irradiating the laminated structure with an energy ray from the laminated structure's one face side, and heating the laminated structure.

Abstract: A holographic data storage medium includes a polymer film which is set up as a storage layer and whose surface structure can be changed locally by heating. The polymer film is set up for the storage of holographic information via the local surface structure of the polymer film. A reflective layer can be provided on the data storage medium.

Abstract: The present invention provides an optical refractive index-modifying polymer composition which can efficiently modulate (change) refractive index upon light irradiation, and exhibits such high storage stability that the once modulated refractive index does not substantially change anymore upon time elapse, and the optical refractive index-modifying polymer composition comprises as a main component a polymer (A) which is a polymer of monomers including an acrylic vinyl monomer represented by the following formula (1): CH2?C(R1)—C(?O)O—R2?CH2 ??(1) wherein R1 represents a hydrogen atom or a methyl group, R2 represents a saturated or unsaturated hydrocarbon group having 1 to 20 carbon atoms, and the molecule may contain a hetero atom or a halogen atom, as an essential component and contains a remaining radical-polymerizable side-chain vinyl group in the molecule, wherein the composition comprises a thermally curable polymer (B) in an amount of 5 to 60 parts by weight per 100 parts by weight of the polymer (A)

Abstract: The hologram recording sheet according to the invention is made up of a base film and hologram sensitive materials sensitive to different wavelength regions formed therein in a desired pattern, or a film and at least two hologram recording sensitive materials sensitive to different wavelength regions laminated on the film with a transparent plastic spacer layer located therebetween, thereby enabling the required diffraction light wavelengths to be recorded on the required sites without producing unnecessary interference fringes. At least two hologram recording sensitive materials sensitive to different wavelength regions are formed on different sites on a film in dotted or striped configuration, the size of which is up to 200 mm or at least twice as large as the thickness of the sensitive material layers, thereby enabling regions diffracting light of different wavelengths to be formed in the form of independent sets of interference fringes.

Abstract: A composition for holographic recording medium, which can be coated in a uniform thickness and enables to simply produce a high definition holographic recording medium is provided. And a holographic medium having a low error rate, high storage capacity, high-performance, high-density, which is produced using the composition for the holographic recording medium, is also provided. The composition comprises a (meth)acrylic acid ester group-containing polymerizable substance, an alicyclic epoxy group-containing cationical polymerizable substance of which is ring-opening polymerized by heat, and a hydroxyl group-containing substance which is reactive with the alicyclic epoxy group-containing cationical polymerizable substance. The holographic recording medium is produced by forming a holographic recording layer on a substrate by applying the composition on the base material and polymerizing the alicyclic epoxy group-containing cationical polymerizable substance and the hydroxyl group-containing substance.

Abstract: Propylene based films and methods of forming the sate are described herein. The propylene based films generally include a core layer formed of an olefin polymer, an embossing layer disposed on an exterior surface of the core layer and entirely formed of a metallocene formed propylene based polymer selected from propylene homopolymers, propylene based random copolymers formed of of polypropylene and polyethylene and combinations thereof, wherein the embossing layer includes an outer surface having a marking formed thereon and wherein the film is capable of retaining the marking thereon.

Abstract: Disclosed are compositions of mixed fullerene derivatives with utility in organic semiconductors, and methods of making and using such compositions. In certain embodiments, the present invention relates to compositions of mixed fullerene derivatives further comprising one or more additional fullerene-based components within specified ranges. In certain other embodiments, the invention relates to methods of producing mixed fullerene derivatives of a specific composition from mixed fullerene starting materials, or pure fullerene derivatives of a specific composition from mixed fullerene derivatives. In yet other embodiments, the invention relates to semiconductors and devices comprising a composition of the invention.

Abstract: There is provided volume holographic data recording media having a recording layer which is capable of recording interference fringes generated by interference of light having excellent coherence as fringes having different refractive indexes and undergoes holographic data recording by an amount of spatial shift distance of not more than 3 ?m which is smaller than that of conventional media.

Abstract: There is described a photopolymerisable composition comprising (a) 75 to 99% by weight of an ethylenically unsaturated monomer or a monomer mixture of different ethylenically unsaturated monomers, (b) 0.5 to 25% by weight of a triglyceride or a mixture of different triglycerides and (c) 0.1 to 10% by weight of a photoinitiator system which activates the polymerisation of the ethylenically unsaturated monomer(s) upon exposure to actinic radiation, wherein the composition is a homogeneous, clear and, at 20° C., liquid mixture. Furthermore, there are described elements manufactured from such photopolymerisable compositions and methods for the formation of light-resistant holograms therefrom. The photopolymerisable compositions are useful, in particular, as recording material for optical elements having refractive index modulation, in particular, holograms.

Abstract: The present invention relates to novel polyurethane compositions which are advantageous for the production of holographic media, inter alia for data storage, but also for optical applications of different types.

Abstract: The present invention provides a fluorine-containing volume holographic data recording material making it unnecessary to provide a step of eliminating a specific solvent even in the case of a thick film, and having high hologram performance and good dynamic range. There is provided a composition comprising a base polymer (a), a liquid monomer (b) and a photo-initiator (c), wherein the base polymer (a) is an amorphous polymer comprising a fluorine-containing monomer as a structural unit and having a fluorine content of 26 to 80% by mass, the liquid monomer (b) comprises at least one liquid monomer (b1) initiating polymerization by means of activated species generated from the photo-initiator (c), the photo-initiator (c) is a compound causing the liquid monomer (b1) to initiate polymerization by exposure to light having excellent coherence and, and a refractive index of the liquid monomer (b) is higher than an average refractive index of a mixture of the base polymer (a) and the photo-initiator (c).

Abstract: A method of producing a volume hologram laminate which can regenerate a hologram image in an arbitrary wavelength by a simple process. The method uses a volume hologram forming substrate which includes: a substrate, a volume hologram layer formed on the substrate and containing a photopolymerizable material, a resin layer, formed on the substrate so as to contact to the volume hologram layer, containing a resin and a polymerizable compound. The producing method includes processes of: a hologram recording process to record a volume hologram to the volume hologram layer, a substance transit process of transiting the polymerizable compound to the volume hologram layer, and an after-treatment process of polymerizing the polymerizable compound.

Abstract: A method for fabricating three-dimensional photonic crystal structures includes providing a layer of photosensitive material; introducing a laser beams into the material; reintroducing the laser beams into the photosensitive material during a second exposure; combining results from at least the first and second exposures to produce a three-dimensionally periodic pattern in the photosensitive material. A related system includes a laser source; a grating array having a plurality of diffraction gratings located thereon; a mask plate located on a photoresist layer and arranged in registration with the grating array; a rotating shutter arranged between the grating array and the laser source, said rotating shutter being suitable for periodically blocking light from the laser source; wherein each of the diffraction gratings is positioned and oriented so as to converge all first-order diffracted spots to a common point lying in a plane of a back side of the mask plate.

Abstract: The present invention relates to a system, as well as articles and holographic recording medium comprising the system, where the system comprises: a polymerizable component comprising at least one photoactive polymerizable material; and a photoinitiator component comprising at least one photoinitiator for causing the polymerizable component to polymerize to thereby form a plurality of holographic gratings when activated by exposure to a photoinitiating light source; wherein when a portion of the polymerizable component has been polymerized to form at least one holographic grating, the unpolymerized portion of the polymerizable component is resistant to further polymerization when not exposed to the photoinitiating light source. The present invention also provides methods for forming at least one holographic grating in a holographic recording medium having such a photopolymerizable system.

Abstract: Double Bragg grating scanner receivers (DBS) and methods thereof based on spinning high-efficiency transmitting or reflecting holograms in photo-thermo-refractive (PTRG) glass provides unlimited field of view while incident angle for all components do not exceed approximately 45 degrees. The devices and methods are highly tolerable to high power laser radiation and has no restriction for the use in any laser systems working in visible and near IR spectral regions. Rate of scanning by DBS is higher compared to known mechanical scanners because the use of thin glass plates with recorded holograms and spinning instead of rocking. The components described herein are holographic optical devices (reflecting and transmitting volume gratings) for visible and near IR spectral regions with absolute diffraction efficiency exceeding approximately 95% and high thermal, optical and mechanical stability.

Abstract: The present invention provides a hologram recording material and a hologram recording medium, which are suitable for volume hologram record and can attain high refractive index change, flexibility, high sensitivity, low scattering, environment resistance, that is, storage stability, durability, low dimensional change (low shrinkage) and high multiplicity in holographic memory recording using not only a green laser but also a blue laser. A hologram recording material comprising: a radical photopolymerizable compound; and a matrix which is a dispersion medium for the radical photopolymerizable compound, wherein the radical photopolymerizable compound comprises a (meth)acrylamide derivative represented by the following general formula (I): CH2?CR1—CONR2—CH2—O—R3 (I) wherein R1 represents H or a CH3 group, R2 represents H or an organic group, and R3 represents an organic group having 3 or more carbon atoms in total. A hologram recording medium 11 which has a hologram recording layer 21.

Abstract: The present invention relates to novel polyurethane compositions which are advantageous for the production of holographic media, inter alia for data storage, but also for optical applications of different types.

Abstract: The invention relates to novel photopolymers based on specific urethane acrylates as writing monomers, which are suitable for producing holographic media, in particular for visual display of images.

Abstract: The invention relates to an optical element, a method for the production thereof, and the usage thereof as an isolator or polarizer. An inventive optical element for a frequency window of the electromagnetic spectrum comprises a first component which has the function of a quarter wavelength plate, and a second component joined thereto which has a circular dichroism. When the first component is exposed to a linearly polarized wave, the optical element can be used as an optical isolator. When, however, the second component is exposed to the linearly polarized wave, the optical element can be used as an optical polarizer. An inventive optical element which is used as an optical isolator can be deployed in laser systems to reduce or suppress the feedback of the laser. In addition, windows can be thus produced which in a specific frequency window are transparent in only one direction. Unidirectional thermal insulation is thereby produced for the infared wavelength region.

Abstract: This invention provides, for example, a highly stable and reliable volume hologram optical recording medium which can suppress an intensity variation, for example, in diffraction efficiency after signal recording and can stably develop a high S/N ratio. The volume hologram optical recording medium includes a recording layer containing at least one compound selected from compounds (A1) having a terpenoid structure, compounds (A2) represented by a formula (I), and cyclic or noncyclic compounds (A3) having at least two double bonds two of these double bonds are located at 1,4-position relatively, wherein R1 and R2 each independently represent an organic group having 1 to 20 carbon atoms, and R1 and R2 may combine to form a cyclic structure.

Abstract: A holographic recording medium in which a thick holographic recording layer is formed without the use of multilayering and without accompanying thickness unevenness, scattering, and nonuniformity of dynamic range, and a method for manufacturing the same. The holographic recording medium 10 is configured by sandwiching a hybrid material layer 14 and a photopolymer layer 16 between first and second substrates 12 and 18. The hybrid material layer 14 contains an inorganic glass and a photopolymer as main ingredients. The photopolymer layer 16 subjected to heat or ultraviolet curing is provided on the dried hybrid material layer 14 such that the combined thickness of this hybrid material layer 14 and the photopolymer layer 16 is uniform. The second substrate 18 is bonded and fixed to this photopolymer layer 16 serving as a bonding layer.

Abstract: A holographic recording medium having a polymer matrix comprising a developer, wherein the holographic recording medium is capable of recording a latent hologram and the developer is capable of developing the latent hologram into a readable hologram by activation of the developer is disclosed. The holographic recording medium is capable of storing large numbers of holograms in the same volume with better signal resolution than previous holographic media by first recording a multitude of latent (or very weak) holograms in the same volume of space, then applying preferably a non-chemical fixing step to develop the latent holograms into readable holograms. The holographic recording medium and method of this invention cause the holograms to increase in diffraction efficiency, thus preventing complications caused during recording of holograms whereby previously recorded holograms interfere with latter recorded holograms in the same volume of space within the media.

Abstract: A method of manufacturing a periodic grating structure for a component. The method includes forming first structured layer including a final periodic grating structure of a first material and a second material filling spaces between individual features of the final periodic grating structure, removing the second material using a first chemical process and annealing a portion of the first material into a third material using a second chemical process.

Abstract: A light concentration device includes: a plate including two principal faces and an edge between the two principal faces, a refractive index gradient existing between the two principal faces, and a diffraction grating functioning in reflection or semi-reflection that cooperates with one of the principal faces of the plate having the highest refractive index, the principal face having the lowest refractive index forming a front entry face for the light, at least one exit zone for the light being disposed on the edge.

Abstract: Photosensitizing dyes are often used in conjunction with a photoacid generator in photopolymerizable materials and in holographic recording media. Typical dyes for these materials are used in the region of the visible spectrum for wavelengths greater than about 450 run. The present invention discloses a number of new 1,4-alkynyl substituted napthalene photosensitizing dyes that have suitably low extinction coefficients coupled with good sensitizing properties for use in such materials at wavelengths in the visible spectrum region of about 400 nm.

Abstract: Disclosed is a volume hologram optical recording medium having a recording layer with low moisture absorption. Specifically disclosed is a volume hologram optical recording medium having a multi-layer structure including a transparent substrate and a recording layer. The recording layer contains a resin matrix (A) and/or a resin matrix (B) and a photosensitive compound (C). The resin matrix (A) is obtained by reacting a polyisocyanate (A1) and a polyol (A2) having a —(C?O)O— group and/or a —O(C?O)O— group, while the resin matrix (B) is obtained by reacting an epoxy compound (B1) having two or more epoxy groups in one molecule and a curing agent (B2). In addition, the recording layer has a moisture absorption rate of 1.5 wt % or less.

Abstract: Embodiments of the invention relate to methods useful in the fabrication of nanostructured devices for optics, energy generation, displays, consumer electronics, life sciences and medicine, construction and decoration. Instead of nanostructuring using colloids of particles, special vacuum deposition methods, laser interference systems (holography), and other low-throughput limited surface area techniques, we suggest to use nanotemplate created by novel nanolithography method, “Rolling mask” lithography. This method allows fast and inexpensive fabrication of nanostructures on large areas of substrate materials in conveyor-type continuous process. Such nanotemplate is then used for selective deposition of functional materials. One of embodiments explains deposition of functional materials in the exposed and developed areas of the substrate. Another embodiment uses selective deposition of the functional material on top of such template.

Abstract: A holographic recording medium is provided. The medium includes a recording layer. The recording layer includes a polymer matrix, a polymerizable monomer and a photopolymerization initiator. The polymerizable monomer includes a monomer being expressed in the following general formula (M1), (M2), or (M3). In the above general formulas, “A” and “B” denote a polymerizable substituent group and a nonpolymerizable substituent group, respectively.

Abstract: An optical medium is provided. The optical medium comprises: a diffusion-controlling matrix framework; at least one photoactive monomer attached to the diffusion-controlling matrix framework in a first state of the optical medium, wherein the at least one photoactive monomer is released from the diffusion-controlling matrix framework by photo cleavage, producing a second state of the optical medium, in which diffusion of the photoactive monomer through the optical medium is possible; and wherein the at least one photoactive monomer is then polymerized or reattached to the diffusion-controlling matrix, giving a third state of the optical medium, when exposed to photo-polymerizing light.

Abstract: A holographic recording medium includes an optically transparent substrate. The optically transparent substrate includes an optically transparent plastic material, a photochemically active dye, and a protonated form of the photochemically active dye.

Abstract: An optical recording medium has a recording layer formed of a plurality of reflection hologram layers. A spacer layer is interposed between the respective reflection hologram layers. The reflection hologram layer is made of a material having a thermal threshold value which allows, when being irradiated with a recording laser beam, local absorbed heat to vary hologram diffraction conditions at a focal position, and allows the hologram to be retained at non-focal positions. The spacer layer is made of a material which is insensitive to a laser beam of a recording wavelength and which has a smaller extinction coefficient than that of the reflection hologram layer.

Abstract: In a process for processing a hologram, a holographic image is formed in a photopolymer layer carried on a substrate. A colour tuning film is applied to the opposed photopolymer layer to form a laminate. The temperature of the laminate is raised and is subsequently cooled and is then exposed to a source of curing electromagnetic radiation.

Abstract: A rotary apertured interferometric lithography (RAIL) system that includes interferometric lithography tools, a mask with a slit preferably with an arc shape, and a rotating stage is disclosed. The RAIL system could create a servo pattern of a recording-head trajectory of a hard disk drive in a master for magnetic-contact printing. The master can could be used to form arrays of sub-micron sized magnetic elements on a magnetic disk media for high-density magnetic recording applications.

Abstract: An illumination device includes a holographic film and a light source, such as a point light source. The point light source is positioned at an edge of the holographic film and has a light emitting face that faces the edge of the holographic film. The holographic film includes a hologram formed of diffractive refractive index structures. The density of the diffractive refractive index structures increases with increasing distance from the light source. Light is propagated from the light source through the holographic film, such as by total internal reflection. The diffractive refractive index structures turn the light, thereby causing the light to propagate out of the holographic film in a desired direction. In some embodiments, the light propagating out of the holographic film has a high uniformity across the surface of the holographic film.

Abstract: A holographic recording medium including an optically transparent substrate is provided. The optically transparent substrate includes an optically transparent plastic material and a photochemically active dye. The optically transparent substrate has an absorbance of greater than 1 at a wavelength that is in a range of from about 300 nanometers to about 1000 nanometers. The holograms recorded in the optically transparent substrate are capable of having diffraction efficiencies of greater than about 20 percent. The holographic recording medium may include a photo-product. A method of making the holographic recording medium, an optical writing and reading method, a method for using a holographic recording article, and a method of manufacturing the holographic recording medium are provided.

Abstract: Disclosed is a photopolymerizable holographic recording medium for data storage that comprises colloidal metal, and which exhibits a threshold for a second stage polymerization which is substantially insensitive to the light used for both forming holograms and interrogating the medium during servo and/or read events. Also disclosed is a method of preparing said photopolymerizable holographic recording medium. Also disclosed is a method for preparing a colloidal without additives in a viscous medium.

Abstract: Disclosed is a volume phase hologram recording material of high sensitivity, high contrast, and excellent record retention properties and also disclosed is a volume phase hologram recording medium using the said material. The volume phase hologram recording material mainly contains a three-dimensional crosslinked polymer matrix, a radically polymerizable monomer, and a photoradical polymerization initiator. The three-dimensional crosslinked polymer matrix is formed from a matrix-forming compound having two photoradically polymerizable unsaturated groups and two non-photoradically polymerizable hydroxyl groups represented by the following general formula (1) and another matrix-forming compound having no photoradically polymerizable group.

Abstract: An optical recording medium includes a support substrate and an information recording layer which is supported on the support substrate and made of a photosensitive material which is irradiated with light to be refractive index modulated and amplitude modulated, thereby recording information. The information recording layer has the shape of a coating which is formed by applying a photosensitive material reversibly dissolved or dispersed in an organic solvent onto the support substrate. The photosensitive material in the shape of a coating, as a photopolymer for hologram recording material, contains the cross-linked matrix to maintain the rigidity of the recording material. The optical recording medium is retained in shape with stability, and particularly prevented from being deformed due to shrinkage, thereby facilitating manufacturing of the optical recording medium.

Abstract: A photosensitive composition and A photosensitive medium for volume hologram recording comprises a photopolymerization reactive compound (a monomer) and any one of the following binder: (a) an organic-inorganic hybrid polymer obtainable by copolymerizing an organometallic compound of the formula 1 “R1m M1 (OR2)n” and an ethylenic monomer and/or its hydrolyzed polycondensate; (b) an organic-inorganic hybrid polymer obtainable by copolymerizing an organometallic compound of the formula 3 “R4m Si(OR5)n” and an ethylenic monomer and/or its hydrolyzed polycondensate; and (c) a binder resin bonded to a metal or a combination use of a binder resin containing a hydroxyl group and/or carboxyl group and a metal chelate compound.

Abstract: The present invention relates to an optical recording composition comprising at least one optical recording compound, wherein the optical recording compound is denoted by general formula (I) and exhibits a molar absorbance coefficient of equal to or greater than 5,000 mole·l·cm?1 at at least one wavelength within an absorption spectrum ranging from 200 to 1,000 nm. In general formula (I), R1 denotes a hydrogen atom or an alkyl group, and Z1 denotes an atom group, the atom group forming a ring structure with a sulfur atom and a carbon atom which are adjacent to the atom group, and a carbon atom bonded to the sulfur atom.

Abstract: The present invention includes systems and compositions of holographic grating structures devices and methods for fabricating such holographic grating structures. The method comprises the steps of preparing a composite mixture comprising a polymerizable matrix, a liquid crystal, and a photo-oxidant dye, producing an interference pattern from two interference beams, wherein the two interference beams originate from a recording laser beam directed by a low energy laser, and projecting the interference pattern on the composite mixture to form a holographic grating structure. As described, the holographic grating structure yields a first-order diffraction efficiency of at least about 30% diffraction efficiency which may be adjusted by the application of an electric field.

Abstract: A hologram laminate is provided. The hologram laminate includes a hologram record layer, and a surface protection layer. The hologram record layer is made of a photosensitive material. The surface protection layer is coated on one surface of the hologram record layer. The surface protection layer is made of an energy ray curing resin.

Abstract: The hologram recording sheet according to the invention is made up of a base film and hologram sensitive materials sensitive to different wavelength regions formed therein in a desired pattern, or a film and at least two hologram recording sensitive materials sensitive to different wavelength regions laminated on the film with a transparent plastic spacer layer located therebetween, thereby enabling the required diffraction light wavelengths to be recorded on the required sites without producing unnecessary interference fringes. At least two hologram recording sensitive materials sensitive to different wavelength regions are formed on different sites on a film in dotted or striped configuration, the size of which is up to 200 mm or at least twice as large as the thickness of the sensitive material layers, thereby enabling regions diffracting light of different wavelengths to be formed in the form of independent sets of interference fringes.

Abstract: To provide photosensitive composition for volume type hologram memory with superior photosensitivity and large differences in reflective index before and after photo-curing and with controllable curing shrinkage. The photosensitive composition for volume type hologram memory of the present invention comprises a photo-curable volume expansion compound and a photoinitiator. According to the photosensitive composition for volume type hologram memory of the present invention, a composition of superior photosensitivity and large differences in reflective index before and after photo-curing and controllable curing shrinkage with photo-curable volume expansion composition can be provided.

Abstract: Some implementations of the invention provide hidden static images. Some such images can only be perceived when viewed from an angle to the normal to a surface. Such images may appear as a solid color when viewed along an axis perpendicular to a surface, but may reveal a hidden image when viewed from an angle relative to that axis. The hidden image may be defined according to interfaces between areas that pass substantially the same wavelength when viewed along the axis, but which pass noticeably different wavelengths when viewed from an angle relative to that axis. The hidden images may or may not be discernable to a human observer. The hidden image may comprise a code that is not readable by an optical scanner positioned to read along an axis normal to a surface, but that is readable by an optical scanner positioned to read along another axis.

Abstract: A holographic recording medium has a recording layer including a radical-polymerizable compound, a first photo-radical polymerization initiator (A) containing a titanocene compound, and a second photo-radical polymerization initiator (B) containing at least one compound selected from the group consisting of an amino acetophenone derivative, an acylphosphine oxide derivative, a benzyl derivative, and a thioxanthone derivative.