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System for prevention of unauthorized copying

  • US 4,791,449 A
  • Filed: 05/30/1986
  • Issued: 12/13/1988
  • Est. Priority Date: 05/30/1986
  • Status: Expired due to Fees
First Claim
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1. A web having phosphor particles uniformly distributed on at least one outer surface of said web, said phosphor particles being substantially white or colorless under ambient room light illumination and which upon excitation by ultraviolet light having a wavelength between about 200 nanometers and about 400 nanometers phosphoresces to emit visible blue radiation having a wavelength longer than said ultraviolet light wavelength, said visible blue radiation being between about 400 nanometers and about 500 nanometers and being detectable on a period of at least 500 microseconds following termination of ultraviolet excitation.

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