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US 2013/0075676 A1Published application
Composite crystal colloidal array with photochromic member
AssigneePPG Industries Ohio, Inc.
InventorsSean Purdy, Jessica M. Williamson, Anil Kumar, Noel R. Vanier, Wei Wang, Shan Cheng, Xiangling Xu
Life of this patent
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Abstract
The invention includes a composite material for use in a security device including a radiation diffracting component that exhibits a first optical effect and a photochromic component that exhibits a second optical effect. The composite material is particularly suited for use in authenticating articles, such as currency.
Claims28
A composite material comprising:
- a radiation diffracting component comprising a crystalline colloidal array of particles received in a polymer matrix and having fixed inter-particle spacing, said radiation diffracting component exhibiting a diffractive optical effect of reflecting radiation at a constant diffraction wavelength at a constant viewing angle;
- and
- a photochromic component exhibiting a photochromic optical effect of absorbing radiation, such that the reflected radiation interacts with the absorbed radiation as a combined optical effect.
(canceled)
A security device comprising:
- a radiation diffracting component comprising a crystalline colloidal array of particles received in a matrix and having fixed inter-particle spacing, said radiation diffracting component exhibiting a diffractive optical effect of reflecting radiation at a constant diffraction wavelength at a constant viewing angle;
- and
- a photochromic component exhibiting a photochromic effect of absorbing radiation, wherein the appearance of radiation reflected by said radiation diffracting component is affected by absorbance of radiation by said photochromic component.
A method of authenticating an article comprising:
- applying a composite material to the article, wherein the composite material includes (i) a first component that diffracts radiation and comprises a crystalline colloidal array of particles received in a matrix, said first component having fixed inter-particle spacing and exhibiting a diffractive optical effect of reflecting radiation at a constant diffraction wavelength at a constant viewing angle and (ii) a second component that is photochromic and exhibits a photochromic effect of absorbing radiation, such that the reflected radiation interacts with the absorbed radiation as a combined optical effect, the composite material bearing an image;
- exposing the article bearing the composite material to a first wavelength such that the radiation diffracting component exhibits a diffractive optical effect;
- and
- exposing the article bearing the composite material to ultraviolet radiation, such that the photochromic component exhibits a photochromic optical effect, whereby the image in the composite material changes.
1 more element
Dependencies are inferred from the claim text.