A halogen concentration (wt.%) in the composition and a solid content concentration (wt.%) in the composition satisfy the following formula (1): [(halogen concentration in composition)/(solid content concentration in composition)]×100≤0.01. {組成物中のハロゲン濃度)/(組成物中の固形分濃度)}×100≦0.01 …(1) - 特許庁