Optically variable pigments used in thermal transfer printing
First Claim
1. A thermal transfer medium comprising a substrate bearing on at least part of one surface thereof a coating of a thermally transferable ink comprising binder and a plurality of discrete particles of optically variable pigment dispersed in the binder.
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Accused Products
Abstract
A thermal transfer medium comprises a substrate bearing on at least part of one surface thereof a coating of a thermally transferable ink comprising binder and a plurality of discrete particles of optically variable pigment (OVP) dispersed in the binder. The ink can be printed using convention thermal printing apparatus and methods to produce on an item such as a personalised card an image the optical properties e.g. colour of which vary depending on the angle of viewing, thus constituting a security feature that is difficult to replicate or simulate, enabling the authenticity of the image-bearing item to be readily checked by visual inspection. The invention also concerns a method of malting the thermal transfer medium, a method of thermal transfer printing using the medium and the resulting printed material.
9 Citations
15 Claims
- 1. A thermal transfer medium comprising a substrate bearing on at least part of one surface thereof a coating of a thermally transferable ink comprising binder and a plurality of discrete particles of optically variable pigment dispersed in the binder.
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11. A thermal transfer medium, comprising an elongate strip of substrate material having on one surface thereof a plurality of similar sets of thermally transferable dye coats, mass transfer colorant layers and thermally transferable ink layers, each set comprising a respective coat of each dye colour, yellow, magenta and cyan, a mass transfer colorant layer and a thermally transferable ink layer, each coat or layer being in the form of a discrete stripe extending transverse to the length of the substrate, with the sets arranged in a repeated sequence along the length of the substrate, wherein each thermally transferable ink layer comprises a coating comprising binder and a plurality of discrete particles of optically variable pigment dispersed in the binder.
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12. A method of making thermal transfer medium, comprising forming on one surface of a substrate a coating of a thermally transferable ink comprising binder and a plurality of discrete particles of optically variable pigment dispersed in the binder.
Specification