Patent ID: 7791984

Claim:
A method for forming an apparatus for indicating the passage of time, comprising: providing a background layer material, said background layer material comprising a first polymer binder, a base material and a background layer color rendering material, said base material is colorless and said background color rendering material displays a background color; performing a background layer material coating procedure to coat said background layer material on a substrate; performing a background layer material drying procedure to dry said background layer material on said substrate so as to form a background layer on said substrate wherein said background layer displays said background color; providing a time passage indicating material, said time passage indicating material comprising a solvent, a redox compound, a reducing agent, and a second polymer binder, said redox compound displays an initial color at an initial reduced state and a final color at a final oxidized state wherein said initial color is different from said background color and said final color is substantially the same as said background color, said reducing agent existing in said time passage indicating material with a predetermined composition such that said redox compound is precisely reduced to said final oxidized state from said initial reduced state; performing an time passage indicating material coating procedure to coat said time passage indicating material on said substrate; and performing an time passage indicating material drying procedure to dry said time passage indicating material on said background layer to form an time passage indicating layer on said background layer, said time passage indicating layer occupying a smaller portion of the area of said background layer, said time passage indicating layer binding to said background layer through physical or chemical bonding formed between said first and second polymer binder, said time passage indicating layer displaying said final color at said final oxidized state which is substantially the same as said background color, such that said time passage indicating layer becomes visually unidentifiable on said background layer to achieve an effect of said time passage indicating layer disappearing from said background layer; wherein after said time passage indicating material drying procedure, all redox compound in said time passage indicating layer is reduced to said initial reduced state, and later when said time passage indicating material is oxidized through contact with oxygen molecules, said time passage indicating layer gradually transforms from said initial reduced state to said final oxidized state, and the color of said time passage indicating layer changes from said initial color to said final color, when said final oxidized state is reached, said time passage indicating layer becomes visually unidentifiable on said background layer, indicating the end of the time passage to be indicated.