Patent ID: 11890888
Assignee: THE GOVERNMENT OF THE UNITED STATES OF AMERICA, REPRESENTED BY THE SECRETARY OF HOMELAND SECURITY
Field: Textile and paper machines (Mechanical engineering)
Classification: CPC B | IPC B

Claim 8:
9. A method of printing on two sides of a substrate using an offset printing press, the method comprising:
positioning a substrate having a front side containing a front security section and a back side containing a back security section onto an offset press;
printing with a first printing unit of the offset press:
a first printed substrate marking in a first ink color in a first saturation; and
a first printed substrate symbol in the first ink color in the first saturation;

aligning the back side of the substrate with ink from a second printing unit of the offset press within a preset threshold to ink from the first printing unit;
printing with the second printing unit:
a second printed substrate marking in a second ink color in a second saturation, the first ink color and the second ink color having a same hue, the first saturation being different from the second saturation; and
a second printed substrate symbol in the second ink color in the second saturation;

printing with a third printing unit of the offset press:
a third printed substrate marking in the first ink color in the first saturation; and
a third printed substrate symbol in the first ink color in the first saturation; and

printing the first printed substrate marking, the second printed substrate marking, the third printed substrate marking, the first printed substrate symbol, the second printed substrate symbol, and the third printed substrate symbol to provide:
a pattern of low saturation and high saturation markings visible in the first ink color when the substrate is viewed with transmitted light;
the second printed substrate symbol being visible in the second ink color in the second saturation when the substrate is viewed with transmitted light; and
the first printed substrate symbol and the third printed substrate symbol visible and indistinguishable when the substrate is viewed with transmitted light.