Legal analysis: the condition of invalid trademark is that the registered trademark is obtained illegally, or by cheating or other improper means. The time limit for declaring a registered trademark invalid is five years from the date of trademark registration, and the owner of a well-known trademark is not restricted by the five-year time limit for malicious registration.

Legal basis: Article 44 of the Trademark Law, if a registered trademark violates the provisions of Articles 10,1and 12 of the Trademark Law, or is registered by deception or other improper means, the Trademark Office shall declare the registered trademark invalid; Other units or individuals may request the Trademark Review and Adjudication Board to declare the registered trademark invalid.

Article 45 of the Trademark Law If a registered trademark violates the provisions of Article 13, paragraphs 2 and 3, Article 15, paragraph 1, Article 30, Article 31 and Article 32 of this Law, the prior obligee or interested party may request the Trademark Review and Adjudication Board to declare the registered trademark invalid within five years from the date of trademark registration. For malicious registration, the owner of a well-known trademark is not limited by five years.