Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Patent
1994-07-06
1997-09-09
Dixon, Merrick
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
156285, 156288, 156289, 156321, 156290, 1563046, C09J 500
Patent
active
056651945
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method of enhancing an image provided by a thermoplastic marking material on a substrate, particularly with a view to establishing the authenticity of the substrate, which material can be activated to take on adhesive properties. Such images are commonly formed using a dry toner of the type used in electrostatic, laser printers or electrostatic photocopying machines.
Modern laser printing machines enable a wide variety of toned images to be produced. The use of heat fusible dry toner for printing is widespread. Such dry toner may be used to form the images on paper which are created by an electrostatic, laser printer controlled for example by word processing, database, spreadsheet or graphical software. The images may be in the form of letter or numerical characters, symbols, graphical compositions or pictorial compositions. For example an image in the form of a signature may be scanned into the controlling computer and held in its data set. That data set may be merged with textual data and the composite printed on an electrostatic laser printer. The signature thereby output is a facsimile formed in dry toner. Such laser printers may be employed in the manufacture of identity cards in which identification details are applied to security printed base stock, and other personalised security printed items such as passports, visas, and items such as tickets.
Office photocopiers nowadays generally employ dry toner as the imaging medium. Such xerographic reproductions are often formed with black dry toner and this photocopied printing is very difficult to distinguish from that on any laser printed original document.
Xerographic, dot image colour copiers are becoming increasingly available. These have the capability of creating realistic full colour facsimiles of the original. Full colour reproductions are created by electronically scanning and colour separating the colour components of the original document or artwork and thereafter recreating the perception of the original colours by the sequential imagewise deposition of yellow, magenta and cyan coloured heat fusible toners, with usually a final black toner tint.
Apart from office copying purposes the use of coloured toner printing is employed for lithographic print proofing purposes. Electrostatic deposition of toner may also be used in the printing stations of certain facsimile transmission machines.
High speed personalised image printing methods are also available. Here toner is deposited under electronic control on cheques and the like so as to personalise the generically printed base-stock with for example the name, address and account number details of the account holder. Thermal transfer tapes may also be employed say with mechanical, "daisy wheel" printers.
The use of dry toner form image formation is widespread. This however makes it very difficult to verify that a particular portion of any given toner print on a document is authentic, the portion being neither added to, removed or altered.
Security documents such as cheques and passports are printed with specially developed materials in special security printing processes and as such are rendered resistant to counterfeiting, alteration and substitution. Personalising images which are printed on such documents in dry toner are less resistant.
Electrostatic laser printing may be used to add personalising details or monetary values to bank cheques and to apply individualising such as personalising or numbering details to passports, tickets, and the like. There is a need to provide simple means for rendering such original images or critical portions of such personalising images secure. In particular there is a need to be able easily to render toned images readily authenticatable and to be able to distinguish an original from a photocopy. There is also a need to prevent removal, alteration or addition of toned images to documents and the like.
A fairly crude method of imparting some security to an identity card is described in GB-A-1165556. In this process, a diffraction grating
REFERENCES:
patent: 5300169 (1994-04-01), Tahara
De La Rue Holographics Limited
Dixon Merrick
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