Insulated wire

1. An insulated wire, comprising:

a conductor; and

an insulating film disposed on the conductor, the insulating film comprising a first layer of a first polyamideimide containing an adhesion improver;

a second layer of a second polyamideimide disposed on the first layer, the second polyamideimide being obtained by reacting an isocyanate component containing 10 to 70 mol % in total of 2,4′-diphenylmethane diisocyanate and dimer acid diisocyanate with an acid component; and

a third layer of a polyimide disposed on the second layer, the polyimide being obtained by reacting an acid component containing 50 to 90 mol % of 3,3′,4,4′-biphenyl tetracarboxylic dianhydride, 5 to 20 mol % of 3,3′,4,4′-benzophenonetetracarboxylic dianhydride and 5 to 40 mol % of pyromellitic anhydride with a diamine component containing 4,4′-diaminodiphenyl ether,

wherein, with regard to a proportion of thicknesses of the first to third layers in relation to the total thickness of the insulating film, the first layer is 10 to 20%, the second layer is 10 to 75%, and the third layer is 10 to 75%.

2. The insulated wire according to claim 1 ,

wherein the acid component of the third layer contains 60 to 70 mol % of 3,3′,4,4′-biphenyl tetracarboxylic dianhydride, 10 to 15 mol % of 3,3′,4,4′-benzophenonetetracarboxylic dianhydride and 25 to 30 mol % of pyromellitic anhydride.

3. The insulated wire according to claim 1 ,

wherein, the second layer is 55 to 75%, and the third layer is 15 to 30%.

4. The insulated wire according to claim 1 ,

wherein a glass transition point (Tg) of the second polyamideimide is 200 to 270° C.

5. The insulated wire according to claim 1 ,

wherein the total thickness of the insulating film is 60 to 200 μm.

6. The insulated wire according to claim 1 ,

wherein the conductor is a rectangle conductor.

7. The insulated wire according to claim 6 ,

wherein the rectangle conductor has a rectangular cross section of 2.0 to 7.0 mm in width and 0.7 to 3.0 mm in height.