Unsprouted seeds need no light at all. They need water, air, a medium and heat, but they don't need light until they have leaves. The cotelydons (the first little nubby round leaves) provide what photosyntesis doesn't until the plant has it's first true leaves.
*edit*
I'm betting what you really meant was what light schedual to use for vegatative growth. My research has led me to adhear to 20 on 4 off. There's a point of diminishing returns after 16 hours of light and the roots like the downtime of darkness.