| 摘要 |
1488483 Credit cards and the like EMI Ltd 23 Oct 1973 [23 Oct 1973] 49272/73 Heading B6A In a method of making a security card which holds a permanent record of a magnetic code, a second layer of magnetizable material is deposited upon a first layer of magnetizable material bonded to a carrier and bearing the magnetic code, the second layer being deposited in a state in which the code is copied into the second layer which is then allowed to set to produce a permanent record of the code before the layers are de-magnetized. As described, the first layer may be a plastics tape 1 bearing acicular γFe 2 O 3 in a binder 2. A metal or alloy second layer 3, e.g. Fe, Co or alloys thereof, or a Ni/Fe alloy, is vacuum evaporated on to the first layer and as it cools through its Curie temperature, its domains are aligned with the magnetic fields associated with the code impressed on the first layer to form a permanent record of the code. In an alternative form, the first layer is metal or alloy and the second layer is a fluid suspension of acicular γFe 2 O 3 particles in a binder and solvent. |
