Vacuum roll coated security thin film interference products with overt and/or covert patterned layers

Abstract

A security thread for embedding in or on a sheet such as a document, currency or packaging is disclosed, wherein the thread has a thin film interference structure deposited thereon. The structure may be a Fabry-Perot structure in the form of a single filter, or may be plural filters, spaced side-by-side. The thread appears to have separated interference filters deposited thereon. Preferably the thread is first roll coated with oil using an oil-ablation technique to remove deposited material in situ in the coating process. A magnetic layer may be deposited within, behind or in front of the thin film interference structure.

Description

CROSS-REFERENCE TO RELATED APPLICATION [0001] The present application claims the benefit of previously filed, co-pending U.S. Application Ser. No. 60 / 487,527, filed Jul. 14, 2003, by Phillips et al, entitled: “IMAGED OPTICAL FOILS,” the disclosure of which is 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 polyester terephthalate (PET) based threads have a thickness of about 0.5 mil or 12.5 microns. By way of example, one of the earliest forms of security threads consisted of reflective foil tra...

AI Technical Summary

Benefits of technology

[0025] In accordance with another aspect of the invention there is provided a machine-readable security device, comprising a web having disposed thereon, a patterned layer of magnetic material sandwiched between two metal layers.

[0026] In accordance with the invention a machine-readable security device is also provided wherein a security thread includes a magnetic material patterned thereon using an oil-ablation process.

[0027] The use of an oil ablation process is a preferred embodiment, allowing the coating and removal of a rolled on pattern within a coating chamber to yield a patterned web having a visible patterned interference structure. Notwithstanding, it is within the scope of this invention to use of other materials having similar properties to oil, wherein its removal is compatible with the coating of subsequent layers in situ. Alternatively, but less preferably, a water soluble polymer coating that can later be removed by washing is possible, however temporary coatings of this sort are not as useful as the application of oil, which can be removed within the deposition chamber.

[0028] This invention circumvents difficulties encountered in wet chemical etching methods for patterning by providing a novel security thread that is optically variable either in reflection or transmission with text or other patterns by using an all...

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 pro...

Images