I resigned from an Australian employer (Company-X) sometime back. During the course of my employment, I developed and partly implemented some ideas as a software application. I was the sole inventor of these ideas. Since leaving the company, I have developed these ideas significantly further and now this is patentable. I am planning to file the patent in Australia & USA assigning the patent rights to my company (Company-Y) that I set up with my wife after leaving Company-X. My employment letter with Company-X had the following clause which I complied with fully in letter and spirit. In fact, I mentioned several times during the course of my employment with Company-X that my work has IP value, but the company didn't ask me to do anything special, most likely because they didn't see any such value in my ideas.
"Patents and Designs If in the performance of your duties you make any inventions, improvements or discoveries in connection with any machinery or other plant, or any process used or which might be used in the business of the Company or any subsidiary or affiliated company, you must fully, freely and immediately communicate the same to the company and if so desired by the Company execute all documents and do all acts and things at the Company's cost which may be necessary or desirable for the purpose of vesting the same in the company."
I am not planning to tell the Company-X about my patent filing at all. In the future, depending upon the situation, I am happy to grant Company-X 'Shop rights' to parts of the patent. This way, Company-X will be able to use my patent ideas without paying me anything while I will be able to license the patent or the software I develop based on that to other companies.
I will not be using the source code that I implemented at Company-X at all. Instead, I will be hiring a freelance software developer to develop the code on a completely different platform altogether. As mentioned, I have significantly developed my initial ideas further after leaving Company-X. In the worst case, I could be accused of using some of the general ideas that I developed first at Company-X.
Please advise if you can think of any complications with a) Company-X challenging the validity of my patent. b) Company-X claiming that they have rights to the software that I am going to develop.
I don't want to discuss these issues with Company-X as their default position will be that all the IP rights belong to them. Do you have any other suggestions for me?