multiple monitors - Maximized chrome shows small line on second screen

I have multiple Monitors connected to my Computer running Windows 10 x64. One of them, my main one, is a 4k Screen and to its left, i have a full-HD one.

When I have Chrome 45 (or any other program) running maximized on the full-HD one, there is also a 1px wide line visible on the 4k screen. When I hove my mouse over this line, the cursors turns into the resize one, but I cannot resize the window as it is maximized. Once I have another active windows placed in front of it, the line is in the background and not visible anymore.

Here is a screenshot to show my problem:

I already tried around in the graphic card settings to check if it has something to do with overscan or similar, but nothing worked.

EDIT It has nothing to do with Chrome. The same problem appears when I have Word on this screen