{TAIL ~ The present inventors} have conducted {HEAD ~ elaborated studies} with the aim of developing a polyamide acid, i.e. polyimide precursor, having photosensitive groups in its main chain which is endowed with about 20 100 times as high a photosensitivity as that of prior products and a heat resistance of 400° C. or above after dehydration cyclization 
{ TAIL ~ The present inventors } have conducted { HEAD ~ elaborated studies } with the aim of developing a polyamide acid , i.e. polyimide precursor , having photosensitive groups in its main chain which is endowed with about 20 100 times as high a photosensitivity as that of prior products and a heat resistance of 400 ° C. or above after dehydration cyclization
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