Secure envelope and method for securing information

A method of detecting information located inside a closed envelope without opening the envelop comprising:

• providing a windowed envelope comprising:
• a first panel with an interior and an exterior side;
• a second panel attached to the first panel to define an interior portion having opposite side edges, a closed edge portion and an opening portion opposite the closed edge portion to provide access to the interior portion of the envelope;
• and a flap for sealingly adhering to an exterior surface of the first panel, the flap having an interior and an exterior side and attached to the second panel at an edge of the second panel opposite the closed edge portion, the envelope comprising thereon an adhesive layer on the interior side of the flap comprising an adhesive;
• wherein a non-transparent window is located on the first panel or the second panel, the window comprising a reducible dye and a microencapsulated reducing agent, which is adapted to irreversibly change to transparent upon heating the window to a temperature above room temperature;
• wherein information is located in the envelope behind the window;
• heating the window to a temperature above room temperature, wherein the window irreversibly changes from non-transparent to transparent thereby exposing the information located in the envelope behind the window.

A windowed envelope comprising:

• a first panel with an interior and an exterior side;
• a second panel attached to the first panel to define an interior portion having opposite side edges, a closed edge portion and an opening portion opposite the closed edge portion to provide access to the interior portion of the envelope;
• and
• a flap for sealingly adhering to an exterior surface of the first panel, the flap having an interior and an exterior side and attached to the second panel at an edge of the second panel opposite the closed edge portion, the envelope comprising thereon an adhesive layer on the interior side of the flap comprising an adhesive;
• wherein a non-transparent window is located on the first panel or the second panel, the window comprising a thermochromic material, which is adapted to change to a transparent window upon heating the non-transparent window to a temperature above room temperature.

A method of detecting information located inside a closed envelope without opening the envelop comprising:

• providing a windowed envelope comprising:
• a first panel with an interior and an exterior side;
• a second panel attached to the first panel to define an interior portion having opposite side edges, a closed edge portion and an opening portion opposite the closed edge portion to provide access to the interior portion of the envelope;
• and a flap for sealingly adhering to an exterior surface of the first panel, the flap having an interior and an exterior side and attached to the second panel at an edge of the second panel opposite the closed edge portion, the envelope comprising thereon an adhesive layer on the interior side of the flap comprising an adhesive;
• wherein a non-transparent window is located on the first panel or the second panel, the window comprising a thermochromic material, which is adapted to irreversibly or reversibly change to transparent upon heating the window to a temperature above room temperature;
• wherein information is located in the envelope behind the window;
• heating the window to a temperature above room temperature, wherein the window changes from non-transparent to transparent thereby exposing the information located in the envelope behind the window.

A method of detecting whether contents of a closed envelope have been read or tampered with comprising the steps of:

• providing a sealed, windowed envelope comprising:
• a first panel with an interior and an exterior side;
• a second panel attached to the first panel to define an interior portion having opposite side edges, a closed edge portion and an opening portion opposite the closed edge portion to provide access to the interior portion of the envelope;
• and a flap for sealingly adhering to an exterior surface of the first panel, the flap having an interior and an exterior side and attached to the second panel at an edge of the second panel opposite the closed edge portion, the envelope comprising thereon an adhesive layer on the interior side of the flap comprising an adhesive;
• wherein a window is located on the first panel or the second panel, the window comprising at least two layers each comprising a thermochromic material, wherein one of the layers is transparent at room temperature and another layer is non-transparent at room temperature;
• and then sequentially,
• heating the layers to a temperature above about 50 C and less than about 100 C, wherein both layers become transparent;
• and
• heating the layers to a temperature above about 100 C, wherein one of the layers is non-transparent and the other layer is transparent.