IP Library › Granted Patent US 12697834
Granted Patent B2
US 12697834 · App. 17/928,031 · Granted Aug 4, 2026

Method of applying a pattern, and security device for an article

Inventors: Graham Triggs-Ramm (Aberdeenshire, GB); Peiman Hosseini (Greater London, GB)
Assignee: E Ink Corporation
B42D25/425B42D25/324B42D25/36B42D25/455B42D25/46B42D25/29
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Quick Facts
Patent No.
US 12697834
App. No.
17/928,031
Granted
Aug 4, 2026
Kind
B2
Abstract

Methods of applying a pattern and security devices are disclosed. In one arrangement, a receiving member ( 10 ) having a layered structure ( 12 ) is provided. The layered structure ( 12 ) comprises a layer of phase change material (PCM, 2 ). The phase change material (PCM, 2 ) is thermally switchable between a plurality of stable states having different refractive indices relative to each other. An embossing member ( 5 ) is stamped into the receiving member ( 10 ). The embossing member ( 5 ) heats a selected portion of the layer CA of phase change material (PCM, 2 ) via contact with the receiving member ( 10 ) during the stamping. The heating thermally switches N phase change material (PCM, 2 ) in the selected portion and thereby applies a pattern of different refractive indices to the layer of phase change material (PCM, 2 ).

Claims (7)

1 . A security device for an article, the device comprising:

a layered structure comprising a layer of phase change material, the phase change material being thermally switchable between a plurality of stable states having different refractive indices relative to each other, wherein:

the layer of phase change material comprises a pattern of different refractive indices at least partly defined by a selected portion of the phase change material in the layer being in one of the stable states and a remaining portion of the phase change material being in one or more other stable states; and

the layered structure comprises a pattern of indentations in a surface of the layered structure, the pattern of indentations being spatially registered with the pattern of different refractive indices in the layer of phase change material, wherein the indentations provide a retroreflective behaviour by which incident light is reflected back towards a light source to a greater extent than would have been the case had the surface of the layered structure been simply planar.

2 . The device of claim 1 , wherein the pattern of indentations is aligned with the pattern of different refractive indices.

3 . The device of claim 1 , wherein the pattern of indentations is substantially identical to the pattern of different refractive indices.

4 . The device of claim 1 , wherein the layered structure comprises a polymer substrate.