The duty of disclosure for patent applicants in Japan differs from the U.S. requirement. In Japan, it is not necessary to submit known prior art.
In applications whose filing dates are before Sept. 1, 2002, applicable Japanese law does not require the submission of any prior art, since there is no duty of candor in such cases. For applications filed on or after Sept. 1, 2002, however, there is a duty to disclose prior art. On the other hand, failure to provide prior art is not a basis of invalidation for the purpose of opposition/invalidation proceedings. However, failure to disclose prior art may be used as a basis for rejection during the examination phase of the prosecution.