Insulated wire

1. An insulated wire comprising:

a conductor,

a bubble-containing insulating layer, directly or indirectly coating an outer periphery of the conductor and containing a thermosetting resin, and

an outer non-bubble-containing insulating layer, directly or indirectly coating an outer periphery of the bubble-containing insulating layer,

wherein bubbles in the bubble-containing insulating layer include flattened bubbles whose oblateness in a cross-section perpendicular to a longitudinal direction of the insulated wire (lateral length of a bubble cross-sectional shape/vertical length of the bubble cross-sectional shape) is 1.5 or more and 5.0 or less, and

wherein a ratio of a number of flattened bubbles among bubbles contained in the bubble-containing insulating layer is 50% or more.

2. The insulated wire according to claim 1 , wherein a porosity of the bubble-containing insulating layer is 70% or less.

3. The insulated wire according to claim 1 , wherein the thermosetting resin is polyester, polyesterirnide, polyimide, or polyamideirnide, or a combination thereof.

4. The insulated wire according to claim 1 , wherein a thickness of the bubble-containing insulating layer is 10 μm or more and 250 μm or less.

5. The insulated wire according to claim 1 , wherein the flattened bubbles are formed by compression in a thickness direction of an insulating layer having bubbles.

6. The insulated wire according to claim 1 , wherein the thermosetting resin is polyesterimide, polyimide, or polyamideimide, or a combination thereof.