Largest Physical Screen Size Tablet

Not so recently, someone asked which tablet has the largest physical screen size.   My answer is that the likely candidate is the Panasonic 4K Toughpad.  This tablet has a 20-inch screen size.

Info: http://shop.panasonic.com/home-and-office/computing-tablets-fax-machines/tablets/UT-MB5025.html#start=1&cgid=tablets

Now, that's my answer if the tablet is to be "portable".  Other devices, such as drawing boards, can be considered tablets and they would have the largest screen size.  One company that makes them is Sharp.  http://siica.sharpusa.com/AQUOS-BOARD

Another alternative is the Wacom Cintiq, which are "Pen Displays" that require a computer and may or may not be considered tablets.  The largest Cintiq has a screen of about 27 inches.
http://www.wacom.com/en-us/products/pen-displays