White Fade on screen occasionally

When i'm working on a job for 35 minutes continuously i'm getting a white shade on screen ( image : http://i.imgur.com/MGHb2eY.jpg ) . When i close the LED and reopen after 3-5 minutes it will became normal .

I've taken the laptop to the service center . and replied as below

"Checked and found Shades on display at times. Tried System

management controller and Pram- no go. Checked with known good external OS- found same. Checked with a known goo external display found display getting without any shades, did apple service tool test failed in display test. Hence the macbook having display related issue need to replace LCD,DISPLAY CLAMSHELL,15.4",GLSY for addressing the issue. Customer denied paid replacement, Hence returning back the device with out repair "

. I'm really thinking why ? when i close and reopen the lap everything goes perfect .

Please reply the problem is with LCD or LVDS cable .