An inventor's notebook is used by inventors, scientists and engineers to record their ideas, invention process, experimental tests and results and observations. It is not a legal document but is valuable, if properly organized and maintained, since it can help establish dates of conception and reduction to practice. The information can improve the outcome of a patent or a patent contestation.
A patent grants its owners the right to sue those who manufacture and market products or services that infringe on the claims declared in the patent. Typically, governments award patents on either a first to file or first to invent basis. The latter is currently true for the United States. Therefore, it is important to keep and maintain records that help establish who is first to invent a particular invention.
The inventor's notebook (also called a journal, lab book or log book) is a systematic device for recording all information related to an invention in such a way that it can be used to develop a case during a patent contestation or patent-related lawsuit.
The notebook is also a valuable tool for the inventor since it provides a chronological record of an invention and its reduction to practice.
A "virtual inventor's notebook", in which one scans note pages and emails them to oneself, would likely serve the same patent contestation protection, the same chronological record, and would be less likely to be lost or stolen. However, confidentiality could be at stake using such techniques.
Though not necessarily following all the guidelines above, journals and notebooks have been kept by many famous inventors, scientists and engineers. Some of the most well-known journals include those of: