looks like some form of signal processing fault m8, if youre lucky, it could be caps failing to supply correct voltage to the processor board, but generally the backlights or something else would go first if it was caps
Is it fairly new as there is a recall on some models check the Sony site ,mine had a similar problem was 3 years old and they said they would repair it FOC collect and return FOC now theres grade a service.
The sets at risk are all 40in LCDs manufactured in 2007 and 2008 - although they may have been on sale until later.
The specific model numbers are: KDL-40D3400, KDL-40D3500, KDL-40D3550, KDL-40D3660, KDL-40V3000, KDL-40W3000, KDL-40X3000, KDL-40Z3000.