Insulated electric wire and varnish for forming insulating layer

#This U.S. National stage application claims priority under 35 U.S.C. § 119(a) to Japanese Patent Application No. 2015-212371 filed on Oct. 28, 2015, the entire contents of which are hereby incorporated herein by reference.

#The present invention relates to an insulated electric wire and a varnish for forming an insulating layer.

#In electrical equipment to which a high voltage is applied, for example, in a motor that is used at a high voltage, a high voltage is applied to an insulated electric wire included in the electrical equipment, and partial discharge (corona discharge) is easily generated on a surface of an insulating coating of the insulated electric wire. The generation of corona discharge may cause, for example, a local increase in the temperature, generation of ozone, and generation of ions, which may result in dielectric breakdown at an early stage and result in a decrease in the lifetime of the insulated electric wire and thus the lifetime of the electrical equipment. Therefore, for insulated electric wires used in electrical equipment to which a high voltage is applied, an improvement in the corona inception voltage is also required in addition to good insulating properties, good mechanical strength, and the like.

#FIG. 1 is a schematic sectional view of an insulated electric wire according to an embodiment of the present invention.

#FIG. 2 is a schematic sectional view of a pore and an outer shell that are included in the insulated electric wire in FIG. 1.

#FIG. 3 is a schematic sectional view of a hollow-forming particle contained in a varnish for forming an insulating layer, the varnish being used for forming the insulated electric wire in FIG. 1.

#In the insulated electric wire proposed in the above patent application publication, for example, when the pores formed in the insulating coating are localized or when the sizes of the pores vary, the pores derived from the thermally decomposable resin tend to communicate with each other in the insulating coating, which may result in the generation of pores having a size larger than the particle size of the thermally decomposable resin. The generation of such continuous pores may cause a decrease in strength and solvent resistance of the insulating coating.

#The present invention has been made on the basis of the circumstances described above. An object of the present invention is to provide an insulated electric wire and a varnish for forming an insulating layer, the insulated electric wire and the varnish being capable of suppressing a decrease in the strength, insulating property, and solvent resistance of an insulating layer while decreasing the dielectric constant.

#An insulated electric wire and a varnish for forming an insulating layer according to embodiments of the present invention can suppress a decrease in the strength, insulating property, and solvent resistance of an insulating layer while decreasing the dielectric constant.