Reactive ester resins, resin varnishes, curable resin compositions, cured materials, semiconductor sealing materials, copper-clad laminates, interlayer insulating materials for add-on substrates, semiconductor devices, and semiconductor packaging.

Abstract

This invention provides an active ester resin, a curable resin composition, and a cured product thereof, which have low softening point, excellent low dielectric properties, and heat resistance. An active ester resin (A) is represented by the following formula (1). (In formula (1), XA independently represents a monovalent organic group represented by the following formula (2), XB independently represents a divalent organic group containing at least one aromatic ring, and XC independently represents a divalent organic group represented by the following formula (3). n is the average of the number of repetitions, and 0 < n ≦ 10) (In formula (2), multiple Rs exist independently, representing hydrocarbon groups or halogen atoms or alkoxy groups with 1 to 10 carbon atoms. r represents an integer from 0 to 4. * represents a bond) (In formula (3), multiple Rs exist independently, representing hydrocarbon groups or halogen atoms or alkoxy groups with 1 to 10 carbon atoms. m represents an integer from 0 to 4. * represents a bond)

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