Patent ID: 11951761
Assignee: TEMPTIME CORPORATION
Field: Measurement (Instruments)
Classification: CPC B  G  C | IPC B  G

Claim 4:
5. The environmental monitor according to claim 1, wherein the environmental indicator material in its initial color state is opaque and has a first color prior to the predetermined environmental exposure, and a background beneath the environmental indicator material has a background color, the first color and the background color are the same or similar so that no color contrast is detectable by naked eye under normal lighting conditions between the first color and the background color, and when the environmental indicator material has been exposed to the predetermined environmental exposure and changes its color state to be transparent, the background and the security material are revealed, so that the environmental monitor does not change apparent color detectable by naked eye under normal lighting conditions and so the security material is visible only when both the environmental indicator material is transparent and the security material has been exposed to the specific light wavelengths.