Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Patent
1999-07-01
2000-10-03
Pianalto, Bernard
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
118 46, 118 58, 118419, 427 7, 427130, 427131, 427132, 427261, 427264, 427265, 427270, 427271, 427289, 427354, 4273855, 427404, 4274071, 428458, 428693, 428694R, 428694TP, 428900, D02G 300
Patent
active
061270342
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention concerns the production of paper or other sheet material for such security documents, and in particular the production of security thread such as described in UK Patent Specification 2227451, which is inserted into such paper/sheet material.
BACKGROUND TO THE INVENTION
The insertion of a security thread into security document paper such as that used for printing bank notes is known. Such threads are typically in the form of an elongate strip typically formed from a plastics film, one surface of which is itself coated with a thin metallic film, and sandwiched between the metal film and the plastics film are regions of magnetic material which are spaced apart and are of such a length (measured in the length direction of the thread), that when moved relative to a suitable electromagnetic reading head, can induce electrical signals having characteristics which can be de-coded to determine the pattern of magnetic material in the security thread.
It has also been proposed to incorporate symbols, letters, numerals or other visually decipherable or machine readable data along the length of the thread and to arrange that this visually and/or machine readable material can be identified at least on one side of the thread and can be inspected (visually or by machine reading) when the thread is incorporated in a security document or bank note.
In particular the readable data may comprise a short description of the document within which the thread is incorporated, and in the case of a bank note may be the currency and denomination of the note.
In U.S. Pat. No. 5,516,153 there is described a security thread in which a plastic carrier is coated with a metal layer to form recessed characters on which is overprinted bars of magnetic ink. Alternatively a thin layer of magnetic pigment may be applied all over the metal layer. Reference is also made therein to EP-A-0330733 which discloses a security thread having a substrate carrier layer made of a tear-resistant material such as polyester.
Security threads are also described in EP Specifications 0400902, 0426801, 0498186, 0659587 and 0613786.
It is an object of the present invention to supply a method and apparatus for producing a preferred form of a composite security thread ie. one having a metallic film for electrical continuity, magnetic encoding to allow the thread to be read using a magnetic reader, and bearing visible data or markings which can be seen by the naked eye.
SUMMARY OF THE INVENTION
According to one aspect of the present invention there is provided a method of manufacturing a composite security thread comprising the steps of: produce spaced apart groups of regions along the length of the film which can be detected by a magnetic reading head, to generate electrical readings for decoding; characters which are to appear visible to the naked eye along a parallel region of the laminated film using a photo resist material so as to protect the metal layer in those regions in which the characters are to appear in the final thread; layer except where protected by the resist; material with an obscuring layer; depositions and the visually readable characters with a transparent or semi-transparent material to provide a barrier to prevent chemical contamination and provide physical protection to the magnetic regions and the visually readable characters, to reduce the risk of damage to the film during the subsequent paper making and printing processes to which the film is subjected.
In an alternative arrangement the aluminium is coated with resist except where the characters are to be formed, and the unprotected aluminium is removed by chemical treatment so that the letters are seen as transparent regions in the opaque reflective aluminium surface.
The plastics film may be a polyester film typically that marketed under the Trade Mark MYLAR.
The resist is preferably applied by a printing process such as flexo printing, rotagravure or silk screening.
Registration between lines of magnetically readable regions and visually readab
REFERENCES:
patent: 4925215 (1990-05-01), Klaiber
patent: 4941687 (1990-07-01), Crane
patent: 5516153 (1996-05-01), Kaule
Governor and Company of the Bank of England
Pianalto Bernard
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