Sorry, I know nothing of Japanese, is like an exhibition of poetry in several languages, and we make signs for decorate the room with many sentences in the diferents languagesWe need more explanations about it to give you what you really mean.
What kind of sign is it? Like a message on a T-shirt? Why you need the sign?
Do you read Japanese?
時間が止まることが必要だ would be a literal translation, rigid and unnatural that no Japanese would say this.
時間よ止まれ would be heard once in a while, this is in imperative form. There's a song with this title.
時間 is the most used word for 'time', but you can also use 時, which is more literary.
If this is the word worrying about the serious problems in the world, I think people have many ways to say this.
時よ、もう進むんじゃない！ (Time, don't move forward anymore!)
時よ、もう進むな！ (Time, don't move forward anymore!)
時間よ、ここで止まれ！ (Time, stop here!)