Vacuum Roll Coated Security Thin Film Interference Products With Overt And/Or Covert Patterned Layers

Abstract

A security device for providing an image having a color shifting region and a visual reference, comprises a substrate having a first side and a second side, a patterned thin film layer on the first side of the substrate for providing the visual reference, and a coating of color shifting ink supported by the first or second side of the substrate for providing the color shifting region of the image, wherein the patterned thin film layer has windows therein, and the color shifting ink is visible through the windows.

Description

CROSS-REFERENCE TO RELATED APPLICATION [0001] This is a divisional application of U.S. application Ser. No. 10 / 891,335, filed Jul. 14, 2004, by Phillips et al, entitled: “Vacuum Roll Coated Security Thin Film Interference Products With Overt And / Or Covert Patterned Layers,” which claims priority from U.S. provisional application No. 60 / 487,527, filed Jul. 14, 2003, by Phillips et al, entitled: “Imaged Optical Foils,” the disclosures of which are incorporated herein.BACKGROUND OF THE INVENTION [0002] The use of security threads for protecting banknotes, credit cards and other valuable documents is well known. A security thread is a strip of material placed on the surface of a banknote document or sheet such as banknote; alternatively a security thread may be serpentined or woven into the banknote paper (a window type effect) to confer additional security (authenticity) to the bank note. Typical dimensions of a hot stamp thread are a width of 1-5 mm, a thickness of 3-4 μm; windowed po...

AI Technical Summary

Benefits of technology

The solution enables the cost-effective, environmentally friendly production of high-resolution, optically variable security threads that are difficult to reproduce, providing enhanced security through visible color shifting properties and hidden magnetic signatures, making them resistant to counterfeiting.

Problems solved by technology

However, these aforementioned threads either take too much time to make and or have other associated problems; for example, it is found that laser etching takes too long to be cost effective, etching by use of chemicals requires multiple steps and is not considered to be environmentally-friendly; holograms can be readily copied, and in many instances the features of the threads are not readily seen by eye by the average person and machines are required to read them.

A major impediment to providing several thin film layers, was residual oil remaining on the images and on non-patterned areas of the web.

This residual oil was detrimental to further thin film coating since left over oil would cause “ghosting”; a process whereby the inhibiting oil is transferred to the back side of plastic film when roll coating, which in turn causes inhibiting oil to be transferred further down the web on the front side.

Left over inhibiting oil also causes adhesion failures to subsequent thin film layers.

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