Japan's government decided to restrict some material exports to South Korea. The restricted materials are fluorinated polyimide, resist - and high-purity hydrogen fluoride. Japan is the world's leader in production of these materials (about 90% of fluorinated polyimide and resist) which makes it difficult for producers to find alternatives.
These restrictions could mean that both Samsung and LG Display may find it difficult to keep OLED production at its current level. Both companies have accumulated a large stock of these materials, but if these restrictions hold up for a long time this could be a problem for the South Korean OLED makers (and a boon for Chinese OLED makers, of course).
The Japanese government decided on these new restrictions following a decision in Korea that Japan's Nippon Steel must compensate Koreans for forced labor during World World Two - while Japan says that this issue was already settled in 1965.
It is not likely that this will be a major issue - the restrictions currently mean that in order to export to Korea, Japanese materials makers will need to apply for export permission which could delay shipments by 90 days - and not restricted altogether. Time will tell whether this issue will escalate, though, or relax...