What causes the laptop LCD to solidify

What causes the Laptop’s LCD to solidify?
My friend who was working abroad sent me a box containing his laptop which he is going to get from me once he has gotten home. After five months he was back home and came to me to get the laptop which was still in the box that I had kept in a glass cabinet.
When we opened the box we were shocked to find out that the laptop’s LCD screen had crystallized or solidified. What caused this?
Can it be repaired or replaced?
Please help.

