The present invention relates to new triazine photoinitiators, a new process for their preparation, and a photopolymer composition comprising a photopolymerizable component and the new triazine photoinitiators. Further aspects of the present invention are a photopolymer comprising said photopolymer composition, a holographic medium which comprises such a photopolymer, a hologram comprising the holographic medium, and a device such a display, chip card, security document, bank note and/or holographic optical element comprising said hologram.

A spectacle lens has a transparent substrate and at least one HOE-capable polymer layer arranged on the transparent substrate. The at least one HOE-capable polymer layer is suitable for forming a holographic optical element. Related methods and apparatus are described.

The invention relates to a photopolymer formulation comprising a component reactive toward isocyanates, a polyisocyanate component, a writing monomer and a photoinitiator containing at least one dye and a coinitiator, characterized in that the coinitiator contains at least one substance of the formula (Ia) ##STR00001## The invention further provides a process for preparing the specific coinitiators and the coinitiators obtainable by this process, and additionally a process for producing a holographic medium using the specific coinitiators, and a holographic medium obtainable using the inventive photopolymer formulation. The invention further relates to a laminate structure comprising an inventive holographic medium and likewise specific borates suitable as coinitiators.

A hologram recording composition includes at least: a photopolymerizable compound containing at least a first photopolymerizable monomer; binder resin that is inactive to photopolymerization; and a photopolymerization initiator. A change in polarity of the first photopolymerizable monomer by photopolymerization reduces compatibility with the binder resin of the photopolymerizable compound than that before polymerization, the compatibility of the photopolymerizable compound before the polymerization being high.

Various holographic films for recording multicolor volume holograms, especially full color volume reflection holograms, and to manufacturing techniques for such film, and to corresponding methods of recording multicolor and full-color volume, in particular volume reflection holograms. We describe a holographic film for recording a multicolor volume hologram, the film including: a carrier; a first photosensitive recording layer sensitive to one or both of red and green laser light; and a second photosensitive recording layer sensitive to blue laser light. Both the first and second photosensitive recording layers include silver halide and have a grain size of less than 30 nm, and at least one of the photosensitive recording layers has a thickness of greater than 3 ?m and less than 5 ?m.

Methods and systems for propagating light into a waveguide are provided. The system may include a light source configured to generate light. The system may include at least one mirror configured to direct the light into one or more rays of light. The system may include a Surface Relief Grating disposed on a Volume Bragg Grating. The Surface Relief Grating may receive the one or more rays of light and may diffract the one or more rays of light. The Volume Bragg Grating may be disposed on the waveguide in which the waveguide may be configured to receive the one or more rays of light from the Volume Bragg Grating and propagate the one or more rays of light throughout the waveguide such that an off-Bragg condition is exhibited by the one or more rays of light propagating through the waveguide.

The invention relates to a photopolymer formulation comprising specific aromatic glycol ethers as writing monomers, matrix polymers and a photoinitiator. The invention further provides an unexposed holographic medium obtainable using an inventive photopolymer formulation, and an exposed holographic medium obtainable by exposing a hologram into an inventive unexposed holographic medium. The invention likewise provides a visual display comprising an inventive exposed holographic medium, for the use of an inventive exposed holographic medium for production of chip cards, identification documents, 3D images, product protection labels, labels, banknotes or holographic optical elements, and specific aromatic glycol ethers.

A nonlinear optical dye includes a compound represented by the general formula (1) below. ##STR00001## In the above general formula (1), each of X.sup.1, X.sup.2, X.sup.3 and X.sup.4 independently represents a hydrogen atom, an alkyl group having a carbon number of 1 to 6, a halogen atom, a hydroxyl group, a nitro group, a cyano group, or a methylsulfonyl group. In the present invention, it is preferred that each of X.sup.1, X.sup.2, X.sup.3 and X.sup.4 independently represents a hydrogen atom, an alkyl group having a carbon number of 1 to 6, or a halogen atom. In the present invention, it is also preferred that the nonlinear optical dye has a dipole moment of 2.1 D or less and a maximum absorption wavelength within a range of 315 to 360 nm.

Gratings may be used in waveguides. Deep surface relief gratings (SRGs) may offer many advantages over conventional SRGs, an important one being a higher S-diffraction efficiency. Deep SRGs can be implemented as polymer surface relief gratings or evacuated periodic structures (EPSs). EPSs can be formed by first recording a holographic polymer dispersed liquid crystal (HPDLC) periodic structure. Removing the liquid crystal from the cured periodic structure provides a polymer surface relief grating. Polymer surface relief gratings have many applications including for use in waveguide-based displays.

A metamaterial optical filter including: a transparent substrate; and a photosensitive polymer layer provided to the transparent substrate, wherein the photosensitive polymer layer is treated using a laser to form a non-conformal holographically patterned subwavelength grating, the holographic grating configured to block a predetermined wavelength of electromagnetic radiation. A system and method for manufacturing holographically patterned subwavelength grating onto the photosensitive polymer layer including: applying a photosensitive polymer layer to a transparent substrate; placing the photosensitive polymer layer between a laser and a mirror; scanning the laser over the photosensitive polymer layer such that a holographic grating is created within the photosensitive polymer layer by interaction between the laser light and light reflected from the mirror; and stacking two or more holographically patterned subwavelength grating layers to form complex metamaterial optical filter stacks.