Briefly describe the examination process of invention patents in China.

A: After receiving an application for a patent for invention, the patent administrative department of the State Council, after preliminary examination, finds that it conforms to the provisions of the Patent Law, and will publish it after 18 months from the date of application. An application for a patent for invention may, within 3 years from the date of filing, be examined in substance by the patent administration department of the State Council according to the request made by the applicant at any time; The patent administrative department of the State Council may, when it deems it necessary, examine the application for a patent for invention on its own. If it is found that it is not in conformity with the provisions of the Patent Law after substantive examination, it shall notify the applicant and ask him to state his opinions or amend his application within a specified time limit. Where the applicant, after stating his opinions or making amendments, still considers that it does not conform to the provisions of the Patent Law, it shall be rejected. If the reasons for rejection are not found after substantive examination, the invention patent shall be granted, the invention patent certificate shall be issued, and it shall be registered and announced at the same time.