Polyimide film comprising omnidirectional polymer chain, method for manufacturing same, and graphite sheet manufactured using same

A method of manufacturing a polyimide film, comprising:

• preparing a polyamic acid solution comprising first unit polymers by mixing a first organic solvent, a diamine monomer and a dianhydride monomer;
• preparing a precursor composition by mixing the polyamic acid solution, at least one imidization accelerator, and at least one dehydration agent;
• and
• forming a polyimide film comprising second unit polymers into which the first unit polymers are converted by imidizing the precursor composition at a variable temperature,
• wherein the molar amount of said at least one imidization accelerator that is added is 0.43 to 0.6 relative to 1 mol of the amic acid group of the polyamic acid, and the molar amount of said at least one dehydration agent that is added is 2.50 to 3 relative to 1 mol of the amic acid group of the polyamic acid
• wherein when a processing condition (a) below is satisfied, at least a portion of the first unit polymers is imidized to the first state, thus forming the second unit polymers, which are omnidirectionally distributed:
• 540 μm<C2*T<610 μm (a)
• wherein C is a sum of a molar amount of said at least one imidization accelerator that is added and a molar amount of said at least one dehydration agent that is added relative to 1 mol of an amic acid group of the polyamic acid, T is a thickness of the polyimide film, and is 30 μm or more to 75 μm or less.