https://en.m.wikipedia.org/wiki/Duty_of_loyalty
https://www.lexisnexis.com/uk/lexispsl/employment/document/3...
Long story short: employees have no implicit "duty of loyalty" except for directors and fiduciaries who are responsible for reporting accurate facts (without which limited liability entities could not function). Companies can make a variety of responsibilities explicit in the employment contract but the core principal is that the employee must agree to those responsibilities when they sign up. This is why we have noncompetes/circumvents and moonlighting clauses: if it aint on paper, it aint going to hold up in court.
The big exception is the criminal code. There are a variety of things an employee can do that arent against their employment contract but could be prosecuted as fraud, creating a virtual duty of loyalty.
Do you live in California? If not, I have no idea what law applies to you and your work.
But if you live in California you are in luck: Section 2872 of the labor code is explicit in this matter. In fact every employee assignment agreement I have handed out to someone I've hired (going back to 1989) has included the text of that section, for example:
in accordance with Section 2872 of the California Labor
Code that the foregoing Agreement between you and Company does
not require you to assign or offer to assign to Company any Invention
that you develop entirely on your own time without using Company’s
equipment, supplies, facilities or trade secret information, except
for those Inventions that either:
a. Relate at the time of conception or reduction to
practice to Company’s business, or actual or demonstrably
anticipated research or development; or
b.Result from any work performed by you for Company. To the
extent a provision in the foregoing Agreement purports
to require you to assign an Invention otherwise excluded
from the preceding paragraph, the provision is against
the public policy of this state and is unenforceable.
This limited exclusion does not apply to any patent or Invention
covered by a contract between Company and the United States
or any of its agencies requiring full title to such patent
or Invention to be in the United States.
This law is widely cited as one of Silicon Valley's advantages over other places.
California went through a period of rational law making, e.g. laws like this, a presumption that drivers know what they are doing regardless of the posted speed limit, etc. Then they went insane (three strikes etc) and the rest is, sadly, history. Still not as crazy as the rest of the USA though.
> a. Relate at the time of conception or reduction to practice to Company’s business, or actual or demonstrably anticipated research or development.
On the other hand stories like google's self driving car team departing to start their own self driving car company, or the tons of people who have left Cisco to start routing companies are legion.
The courts in California rarely side with the company, (so if you work on billing for Google and decide to do some machine learning on the side, even though Google does a lot of ML work no court would find in their favor -- though I doubt google would go after you anyway). But at the opposite end of the spectrum, a court in Texas have ruled that simply the thoughts in the head of an employee are a company's (DSC) proprietary information -- the ultimate non-compete (non-competes are illegal in CA).