I will make a patent application. There will be names of two persons in the patent file. We want to share patent right not equally but 80% - 20%. How can that be possible? How can we specify this in the patent application? Or will it be specified in an agreement?
The laws may vary from country to country, but under the United States Code, co-inventors are each considered to have 100% ownership of the invention unless otherwise specified in an agreement.
Therefore, before you start the application process, you should have an agreement in writing that clearly states the terms of co-ownership for each inventor of the patent (percentage royalties, duration, etc.), and have this signed by each inventor. Many organizations (e.g., universities and large corporations) have some established procedure for this. If you are a small business, the first thing you should do is to hire a patent attorney to make certain nothing goes wrong with this part of the process. If a mistake is made here, it can become costly if not impossible to correct later.
Each co-inventor will still need to sign a declaration or oath. The USPTO provides these forms.
Malek, M. Uncooperative Inventors, July, 15 2013.