Patent ID: 7684997
Filing Date: 2010-03-23
Classification: B65D,G07B

Abstract:
1. A machine-readable color envelope comprising: a paper dyed with a reversible negative photochromic dye, such that the paper substrate forms an envelope-shaped container and the color of the paper substrate over the entire outside surface of the envelope-shaped container is controlled by the reversible negative photochromic dye; and a postal indicium, printed on the paper substrate; wherein applying a first photochromic activation energy to the machine-readable color envelope changes the color of the paper substrate in the background of the area over which the postal indicium is printed from a first paper substrate color state to a second paper substrate color state; wherein applying a second photochromic activation energy to the machine-readable color envelope, or the passing of a period of time, changes the color of the paper substrate in the background of the area over which the postal indicium is printed from the second paper substrate color state to the first paper substrate color state; and wherein the readability of the postal indicium by a machine is improved when the color of the paper substrate in the background of the area over which the postal indicium is printed is in the second paper substrate color state, compared to when the color of the paper substrate in the background of the area over which the postal indicium is printed is in the first paper substrate color state.