Without naming him, she said in a post on her Facebook page that she wanted to talk in the spirit of the Me Too social media campaign to expose the true scale of abuse experienced by women, which was prompted by the allegations made by Hollywood actresses against film producer Harvey Weinstein.
The director told Denmark's Jyllands-Posten newspaper it was "not the case" that he had sexually harassed the singer.
"I walked away from it and recovered in a year's time".
She went on to describe an on-set encounter with the director, who punished her and framed her as being "difficult" for turning down his advances.
Falling in line with Björk's view that she "was framed as the hard one", Peter Aalbæk Jensen, who produced the film, also denied Björk's claims.
"It feels extremely hard to come out with something of this nature into the public, especially when immediately ridiculed by offenders", she said.
"That woman was stronger than both Lars von Trier and me and our company put together", he said. "I am anxious though that other actresses working with the same man did not".
3 during the whole filming process there were constant awkward paralysing unwanted whispered sexual offers from him with graphic descriptions, sometimes with his wife standing next to us.
The post has been created as the artist feels "it is the right time especially now when it could make a change".
Bjork added that attempting to dismiss her account by accusing her of "being difficult" paralleled the "Weinstein methods" of "bullying" victims who dared to speak up.