From Wikipedia:

BD-R LTH is a write-once Blu-ray Disc format that features an organic dye recording layer. "Low To High" refers to the reflectivity changing from low to high during the burning process, which is the opposite of normal. The advantage of BD-R LTH is it can protect a manufacturer's investment in DVD-R/CD-R manufacturing equipment. The manufacturer need only modify current equipment; it need not invest in new production lines. This is expected to lower the cost of disc manufacturing.[26]

Old Blu-ray players and recorders cannot utilize BD-R LTH; however, a firmware upgrade can enable devices to access BD-R LTH. Panasonic released such a firmware update in November 2007 for its DMR-BW200, DMR-BR100 and MR-BW900/BW800/BW700 models.[27] Pioneer was expected to ship the first LTH BD drives in Spring 2008.[28] Sony upgraded the PlayStation 3 firmware enabling BD-R LTH reading in March, 2008.[29]

In 2011, France's Ministry of Culture and Communication conducted a study on the suitability of data archival of LTH (low to high) discs compared to HTL (high to low) discs. The data they collected indicated that the overall quality of LTH discs is worse than HTL discs