I purchased a Samsung Z140 phone at the weekend, though am having trouble getting the display screen to stay on when you flip the phone down.
I've gone into settins and it allowes you to select different clocks, so as you can see the time etc..when you flip the phone down. Though it only stays on the screen for about 3 seconds before the screen goes completly black. Does anyone know of a work around, so as the clock stays on the screen all the time.
Sorry, I don't have a Z140 but some thoughts on your problem.
I'm going to guess at a power save option or a faulty handset. Most flip phones will turn off the backlight of the external display after a few seconds, requiring a button push (normally on the side of the handset) to re-awaken the backlight for a few seconds. But the display normally shows the time via ambient light reflected off the back of the LCD display.
If yours is not doing this then there could be a genuine fault - to blacken an LCD takes intent as its normal state is to be translucent (i.e. you can see the reflective back surface of the LCD). If it is not a fault, then it could be a setting in the Display or Power Options menus.
If you can't find it then maybe a trip to the local dealer where you got it from will get you a result if they know how to fix it, or get it replaced/repaired.
The Z500 is the same. The clock or the outside display LCD image only shows for about 15 seconds. This is to preserve battery power I imagine. The clock is a gimmick really as the external screen has some network icons and a digital time display which is shown at all times.