Emi, LLC

Ralph R Pearce

Magnetic recording media including permanent structures of aligned acicular particles have been proposed as a means of identifying and authenticating a medium. A structure which has an improved remanence difference signal is described. A method of making and examining such a structure is described. Arrangements of such media and record/read-out apparatus by which information can be recorded and read-out without interference from the structural remanence differences are described. The use of the media for security documents such as credit cards is described.

Magnetic recording

A method of printing wherein magnetic particles dispersed in an ink are selectively orientated prior to printing onto a document where the particles are aligned on a carrier while the ink is in a low viscous state and the printing is effected when the ink is in a high viscous state. The method by which the viscosity is changed is the selective application of heat.

Security document

Magnetic recording media including permanent structures of aligned acicular particles have been proposed as a means of identifying and authenticating a medium. A structure which has an improved remanence difference signal is described. A method of making and examining such a structure is described. Arrangements of such media and record / read-out apparatus by which information can be recorded and read-out without interference from the structural remanence differences are described. The use of the media for security documents such as credit cards is described.

A security document has a carrier and two layers of magnetizable material one overlying the other, the carrier and layers being all bonded together. One layer is for the recording of information and the other layer has a magnetic structure which can be examined for verification purposes. A preferred method of making the structured layer is to deposit magnetizable material to form the layer within the influence of a magnetic field from a recording on the information layer which is of the form of the structure. The recording is erased when the structured layer has been formed. The security document may be a credit card, a bank note or other valuable paper.

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West Drayton, United Kingdom

Ralph R Pearce