If I say Mincha with tefillin on and then when I take them off it is already after shekiah (sunset) should I still say the bracha "asher kideshanu bemitzvotav vetzivanu lishmor chukav"?

Written by Rav Bar-Hayim

Yes, one should say this bracha before one removes one's tefillin for the last time on a given day regardless of whether one does so before or after shekiah.