IE 10 and 11 use a distinct syntax for downloading or saving blobs to the client machine. Once you’ve created a blob, use:
window.navigator.msSaveBlob(blob, 'file.txt');
or
window.navigator.msSaveOrOpenBlob(blob, 'file.txt');
to trigger the file save or file save/open dialog.
For more info, see http://msdn.microsoft.com/en-us/library/ie/hh673542(v=vs.85).aspx