Display brightness can't be changed under Windows (Lenovo X240)?

I upgraded my ThinkPad X240 from a TN panel to an IPS panel. Now I have the problem that under Windows and even under Windows, the display brightness can't be regulated, it is always at 100%. However, under different Linux distributions, it works perfectly.

Does anyone know what it could be? Have tried everything under Windows with drivers and such.

Is that too bright or too dark the current 100% brightness

The brightness is always at 100% so the day is fine but in the evening and at night too bright.

And it's not laptop or tower

Is a Thinkpad… But it seems to be on the panel, I'll grow another one.

OK