wellin theory it shouldn't affect the lcd at all. Microwave ovens are optimised to excite water as there is no water in a lcd there should be no effect. Metal though acts as a kinda of antenna and traps the energy from the waves converting it into electricity hence why when metal is in the microwave it actually sparks and has extremes of heat.
The other issue is all the metal inside the laptop might keep it safe due to a fahrah day cage (the name probably isn't right) this is where the space between the setions of metal is smaller then the wavelength of the radiation and so the microwave cannot pass through it, this is how microwaves keep the microwaves contained within the over its also why when virgin built theit super high tech trains they were a flop because they decided to put metallic windows so no mobiles worked and the wireless internet which they were providing didn't work as each carriage would need its own router lol