I could be either a loose video cable connection at either end, motherboard or LCD panel, a damaged video cable where it passes through the hinge to get from the motherboard to the LCD panel or worst case a faulty LCD panel.
Here's the owner manual for the laptop.
Go to p.69 to view the procedure to remove the display assembly. This will allow you to inspect the video cable connection on the motherboard to ensure that it is secure and also to inspect the video cable where it passes through the hinge. If it all appears to be OK continue on with the manual to see how to remove the LCD panel as this will allow you to inspect the cable connection on the panel.
If the cable is faulty usually there is a part number printed on it somewhere, (maybe CN-0TC8Y3 but not totally sure about this), the same with the LCD panel. Search online using the part number only to find suppliers that suit you best.