How to Leave the Display on in an iPhone
Your iPhone turns off its display to conserve battery life and to prevent accidental use. However, there are times when you need your iPhone to remain on for an extended period of time to keep up with you. Instead of reawakening your iPhone every one to five minutes, tweak the settings to leave your iPhone's display on until you manually lock it.
Tap "Settings" on your home screen.
Tap "General" and then "Auto-Lock".
Select "Never" at the bottom of the list.
Press the "Home" button to return to your home screen.
Tips & Warnings
- Don't forget to revert to your old auto-lock settings or press the "Sleep/Wake" button to turn off your display when you are done, otherwise the battery will become depleted at a rapid rate.