Non-obvious or nonobvious?

Solution 1:

In US patent law (PDF) they use non-obvious.

For example:

103 Conditions for patentability; non-obvious subject matter.

In UK patent law (PDF) they use not obvious.

For example:

An invention shall be taken to involve an inventive step if it is not obvious to a person skilled in the art...

New Zealand uses both non-obvious and not obvious.

For example:

The objective of the international preliminary examination is to formulate a preliminary and non-binding opinion on the questions whether the claimed invention appears to be novel, to involve an inventive step (to be non-obvious), and to be industrially applicable.

and

The description shall first state the title of the invention as appearing in the request and shall: ...

(vi) indicate explicitly, when it is not obvious from the description or nature of the invention ...

Canada (PDF) uses not be obvious:

28.3 Invention must not be obvious

Eire uses not obvious:

An invention is considered as involving an inventive step if it is not obvious to a person skilled in that area of technology...

From this sample I surmise that non-obvious is the form you want although you might consider not obvious.