Acer Aspire screen turns black

Question

I have been using Acer Aspire 4530 for about 1 month and since last two days the screen turns black after using it for one or two hours. The power light is still on. capslock light and numlock light is still as it was, but CPU light is off. The only way I could do is to turn it off by pressing power button for 5 secs and turn it on again. The problems occurs whenever it was plugged or not. Any suggestions to fix this?