Abstract: An insulating varnish forms an insulating coating film having a shape that corresponds to the shape of an opening of a die, having a uniform thickness. The insulating varnish is applied onto a surface of a conductor, subsequently passes through a die to remove the excess applied insulating varnish, and is then dried or baked to form an insulating coating film on the surface of the conductor. The insulating varnish has a viscosity of 10 Pa·s or more measured by a B-type viscometer at 30° C. The insulating varnish preferably contains no filler, and is preferably a polyimide precursor solution. Since the insulating varnish has a high viscosity, baking and solidification can be performed while maintaining a shape formed when the insulating varnish passes through a die.

Abstract: An insulating varnish forms an insulating coating film having a shape that corresponds to the shape of an opening of a die, having a uniform thickness. The insulating varnish is applied onto a surface of a conductor, subsequently passes through a die to remove the excess applied insulating varnish, and is then dried or baked to form an insulating coating film on the surface of the conductor. The insulating varnish has a viscosity of 10 Pa·s or more measured by a B-type viscometer at 30° C. The insulating varnish preferably contains no filler, and is preferably a polyimide precursor solution. Since the insulating varnish has a high viscosity, baking and solidification can be performed while maintaining a shape formed when the insulating varnish passes through a die.

Abstract: Provided are a varnish mainly containing a polyester imide and capable of forming a low-permittivity insulating layer, as well as an insulated electronic wire achieving low permittivity by using the varnish. The varnish mainly contains a polyester imide resin obtained by reacting a carboxylic acid including a dicarboxylic acid, or an anhydride or alkyl ester thereof (carboxylic acid or derivative thereof), an alcohol, and a diamine compound with one another. In the varnish, adjustment is made such that a molar ratio (OH/COOH) of hydroxyl groups of the alcohol to carboxyl groups of the carboxylic acid or derivative thereof becomes 1.9 or less or such that a content of highly polarized imide groups per unit amount of polyester imide chain is reduced by increasing molecular weights of the raw material monomers.