Samsung lcd dark on one side ?

[buncey]

good afternoon guys.

i have got a  Samsung lcd model LE40f86BDX.

lcd: LTA400HH-L01

when cold the right side of tv is very dark however it will clear up once tv has been on for about 10 mins and tv will work ok.

also i have noticed when cold i can get the picture to go ok without waiting to warm up and get picture ok straight away if i tap the back of the tv?.  i checked all obvious  cables inside and all secure.