The initial batch (alpha testors) of the WanHao Duplicator 7 does not appear to use glue or other mechanical attachment of the LCD protective overlay and actual LCD module. Please note that this was addressed in the latest revision of the D7 (now Beta shipping March 1st). They are made of extremely thin yet tough glass, not unlike the typical smartphone screen and digitizer. The current screen as a rubber silicone like layer around the edges that conform and help to hold it in place in the lower milled aluminum base plate of the printer. The vat resin tray and FEP film com into direct contact with the LCD for maximum sharpness of the resulting imaged layer in resin. Overall, this structure can work well to produce outstanding high resolution prints. The problem is that when removing the vat resin tray and FEP film, a suction action can occur that lifts the entire LCD module from the lower base frame of the printer. When this happens, the LCD glass module that is attached under the protective layer and was recessed into the pocket of the aluminum plate can now lift out and become misaligned, and massive pressure is exerted on the glass if it is pressed back into the milled pocket with the slightest misalignment. This can and often does crack the LCD. This has been reported to WanHao and hoping changes in mounting and attachment can be made.
That all said, PREVENTION is the key watchword of the day. By using tape to attach the LCD module to the base to prevent it from being lifted and subsequently damaged, we can help reduce the risk of a damaged LCD. In my personal example, I used Kapton tape 1 inch wide that I happened to have on hand, however, many tapes would work. The key is to observe the actual edge of the screen VS the imaging area and only apply tape to the black edge which never transmits light. Also cleaning the aluminum with rubbing alcohol and a paper towel can improve adhesion of the tape and further prevent accidental lifting of the LCD.