iPhone 4 screen went black and won't reboot or show anything on the screen whatsoever.

I was using my iPhone 4 with iOs 5.1.1 in a fully charged battery this morning and was reading a news app when all of a sudden the screen began to almost pixelise amd then went black. I've has it go black before but was able to just do a reboot using home and lock button method; but this time nothing works. When I plug it into my computer now, it only sees it as an iPhone in recovery mode and says I have to restore. But the screen has continued to stay black, never showing any apple icon or anything. Did my phone just die??