With a wide blade (a common razor knife blade is used here) carefully cut and pry up along each edge.
The filter is held on with a double stick tape gasket. Gradually work the filter off the sensor.
Do not pry with a narrow tool or damage to the filter or sensor will result.
This is actually the sensor from a KM 5D as I didn't take a photo of removing
the filter on the NEX but the procedure is the same.
Note older style DIP package on the 5D sensor.
The NEX appears to use a BGA on a ceramic substrate.