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Method for making an identification card having features for testing in incident and transmitted light

  • US 4,711,690 A
  • Filed: 12/18/1985
  • Issued: 12/08/1987
  • Est. Priority Date: 08/24/1982
  • Status: Expired due to Fees
First Claim
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1. A method of producing an identification card comprising the steps ofproviding at least two layers of synthetic material, said layers differing with respect to transparency and softening temperature;

  • providing at least one surface of the layer having the higher softening temperature with a relief structure without throughgoing openings said structure corresponding to a pattern or characters and said relief structure being provided by either excavation or deformation of said layer up to a certain depth;

    superposing said at least two layers such that the at least one surface of the layer being provided with said relief structure is adjacently situated to said layer having the lower softening temperature;

    applying heat and pressure all over the surface of the superposed layers for laminating said layers, wherein the heat is applied such that the temperature within the superposed layers during the laminated process is higher than the softening temperature of the layer having the lower softening temperature but said temperature being lower than the softening temperature of the layer being provided with said relief structure such that the layer having the lower softening temperature equalizing said relief structure by at least partially filling impressions of the surface relief structure such that the laminated structure has a constant thickness with respect to its outer dimensions, said layers having different transparencies locally varying with respect to the thickness such that when subjected to transmitted light the areas of greater thickness within the layer of less transparency appear to be darker than the surrounding areas whereas when subjected to incident light said areas having a higher color-intensity than the surrounding areas and wherein said layers are provided within said identity card such that the relief structure is covered at one face thereof only by transparent layers such that said relief structure is visible from the outside of the card.

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