it looks like the Screen inverter has gone defective you will have to replace it,
The display inverter is the circuit which gives the power to the screen backlight.
connect to an external monitor and check if the display is coming, if it is coming then you will have to find an inverter online and replace it.
you can buy the part from here: [http://www.laptop-parts.gr/en/LCD-Inverters?for=Toshiba,DynaBook&page=51|LINK]
i would suggest replacing the laptop since it is outdated, if the circuits starting to fail most probably other issues will come in the future