Does Iphone4 use LG's IPS screen or Hitachi's? What's the difference between them?

Ip uses LG's ips, which was jointly developed by Hitachi, Panasonic and Toshiba, and then LG bought a patent for production and improvement.

Speaking of ips, Hitachi has done a good job. It is only developed and promoted in LG, which makes people feel that LG is doing well.

Retina is a display technology, its function is to compress high resolution on a small screen, so that PPI exceeds the resolution that human eyes can see. For example, ip compresses 960×640 to 3.5 inch screens, making the ppi reach 326, while LT26 compresses 1280X720 to 4.3 inch screens, and the ppi even exceeds ip4.