It's nice that e-paper has suddenly gotten a lot more affordable. I wonder what the cause of that is--did important patents recently expire, or anything like t

It's nice that e-paper has suddenly gotten a lot more affordable. I wonder what the cause of that is--did important patents recently expire, or anything like that? Still, it is most interesting in larger sizes, preferably full A4 for purposes of reading ArXiv preprints and other pdfs at their intended size.