US Patent 9580555 Transparent polyamide-imide resin and film using same

Disclosed are a transparent polyamide-imide resin and a film using the same, which can be colorless and transparent, can show excellent thermal stability and mechanical properties, and can have low birefringence, making it possible to serve in various fields including a semiconductor insulator, a TFT-LCD insulator, a passivation layer, a liquid crystal alignment layer, materials for optical communication, a protective film for a solar cell, a flexible display substrate and the like.