AFAIK Giant purchases tow (carbon thread) from Toray then weaves it into their own prepreg, they are supposedly the only manufacturer to do this, everyone else purchases the prepreg.

I had found a link on bicycling.com but it is now dead, but I do have much of the text from the interview in the article

I dunno where the conversation has gone since the first page, but I found this bit quite interesting YMMV...

interview with Tony Lo, Giants CEO
"So without knowing too much we say, "Hey, if we can make one good carbon fiber bicycle that's a good way to really differentiate Giant from the other bike companies. As a manufacturer, we're always thinking about how to make the best product, with the best production, and make the cost more reasonable so more people can afford it and enjoy it. So it was a good idea, but a bit premature given that we didn't know much about it.

The project was called 858, because it started in 1985 in August. So we started research and what we found is it was very difficult. We did a lot of research on the material. We got fibers from companies in Japan, from the UK and the U.S. and tested everything and identified that in Japan, Toray was the finest in carbon fiber materials. But at that time no one could really supply the prepreg (a carbon fiber sheet with the resin already in it), which currently they do. So we needed to figure out how to do prepreg, which we need for bikes, but Toray can only supply thread (carbon fiber without the resin which cannot yet be made into tubes for frames). So after all the research we find a German company that made a prototype machine to weave the thread in the amounts we needed. We found them because were also looking at resins, and the best was in Germany or Switzerland. And so we went to Ciba to learn about resins from them. They refered us to this German machinery company. They were surprised that we're in bikes and not aerospace. So when we finally decided to go forward with our own project it was very international; we were using Toray thread and Swiss resin and this German machine and did it all in house in Taiwan. "