Is naming the correct inventors important for filing a patent application?
We have here a situation where we do not want to name an inventor in a patent application because he has left the company.
He has no rights to the invention and to the patent but he still insists on being named as an inventor.
What happens if we do not name him as an inventor? Will a later granted patent be potentially invalid?
I have never heard of a similar case in which this played a role.
Under German law and under Singapore law one has a legal claim for being named as an inventor, but it does not have consequences for the validity of the patent. Nobody undertakes the hassle to assert such a useless claim in court. Inventors usually have many patent applications, so that one application more or less does not count.
This may be different if the rights to the invention are not clear. But as you have said that "he has no rights to the invention and to the patent", there is no need to elaborate on that. I will do so below with respect to the situation in the U.S. Be careful, the same situation may arise in Germany and in Singapore.
Please note that the answer to your question is very different under US law!
U.S. patents must have all inventors properly named. Deciding who is an inventor is a complicated task and great care must be taken to not add or omit people who are not inventors. It is possible that failure to properly name the inventors could result in losing the US patent.
This means also that if inventors have been improperly added or omitted, the patent must be corrected or it could be declared invalid. The USPTO requires a petition stating that it was an error and all the parties and assignees must make the application, agreeing it should be corrected. If all parties don’t agree, the assignee can file a request for reissue of the patent naming the correct inventors. A court can also order the USPTO to make the correction. If the inventors can be corrected, the error won’t invalidate the patent. If it cannot be corrected, the patent can be lost.
Having the wrong inventors often arises when the patent becomes valuable—when the product or process is successful and those involved feel they’ve been wrongly excluded and want to be included.
The US is also very different from the rest of the world when it comes to ownership of a patent. Initially, every inventor owns an equal right to the US patent, no matter what they contributed.
This means that each inventor can do what they want with the patent. They can sell it, license it, make and sell the product or process covered by the invention, all without the permission of any other inventor. They can also frustrate any lawsuits, since all owners have to be joined in a lawsuit.
To prevent each inventor from doing what they want, the rights are assigned to a single person or entity. Once assigned, that person or entity owns all rights. An assignment is a legal document transferring the rights of the inventors (= assignors) to the owner (= assignee).
In the case that an inventor is missed out, even with an assignment in place, one may find that someone else owns the same rights as the registered owners on the patent. Each inventor owns an undivided interest in the entire patent, no matter their respective contributions. That means that a joint inventor of just one claim enjoys a presumption of ownership of the entire patent.
That opens a very interesting defense route in patent infringement: in 1989, Ethicon, a manufacturer of surgical instruments, filed a patent infringement suit against a competitor, United States Surgical, over U.S. Patent No. 4,535,773. The inventor named on the patent was Dr. Inbae Yoon. Yoon granted Ethicon an exclusive license to practice his invention. The patent had 55 claims but only two claims were asserted against U.S. Surgical: claims 34 and 50.
During the lawsuit, U.S. Surgical learned of a co-inventor named Young Jae Choi. Choi was an electronics technician who collaborated with Dr. Yoon for 18 months. Choi could prove that with simple dated notes and drawings. Choi had then granted U.S. Surgical a retroactive license to the patent. US Surgical then asked the court to add Choi as an inventor. The court agreed finding that Choi had co-invented claims 33 and 47, and these were two claims that were not even involved in the lawsuit. And the court dismissed Ethicon’s lawsuit.
This is what I see happening often: companies collaborate with outside suppliers that contribute to the company's inventions, and these suppliers become inventors. No, it does not mean that because a company has hired and paid someone to assist in developing a product that they own the results. Or they think that it was their idea and that they do not need to add the experts. Many times, they don’t even mention it to us, their patent attorneys, thinking it is not important. But that supplier might be an inventor of just one claim and have equal rights to the entire patent. And whether they are listed as an inventor or not, they may be able to license their patent just like Choi did.
Avoid this by including appropriate assignment statements into the supplier co-operation agreements that transfer their rights to your company. The same should be done in all employees agreements and consultants and freelancer agreements when they are hired.
Moreover, keeping detailed, dated records of the development and the contributions of everyone in a company can provide important evidence for the future.