Crystal polymorphism of kcnq 2-5 channel activator

Crystal polymorphism may be present in a crystalline compound. In cases where there is crystal polymorphism, depending on the crystal form, solubility, dissolution rate, or stability against heat, light, humidity and the like are different. Accordingly, in the manufacturing of medicaments, selecting a crystal form of the drug substance most suitable for the indicated disease and dosage form is a very important task. The present invention is related to a novel crystal form (A crystal, W crystal, and hydrate crystal (H crystal)) of compound I having a strong opening action with respect to KCNQ 2-5 channels.