plotting – Exported Frame Tick Labels Don’t Look Anti-aliased

I have a frame with labeled gridlines and I’m exporting it as a PNG. I am using ImageResolution to scale it up. This is the output I get when there is no function being plotted (it has an alpha channel, and my picture viewer puts a black background behind it):

enter image description here

The text used for the font looks a little rough:

enter image description here

Is there any way to get it to not look so jagged around the edges of the font? Or perhaps even use Matex to make it look better?

Right now I’m using:

FrameTicks -> {b1,b2}

where

rx := {-2 (Pi), 2 (Pi)};
ry := rx;
a1 = Table(i*(rx((2)) - rx((1)))/8 + rx((1)), {i, 7});
a2 = Table(i*(ry((2)) - ry((1)))/8 + ry((1)), {i, 7});
b1 = {#, fractionToRow@#} & /@ a1;
b2 = {#, fractionToRow@#} & /@ a2;

and I’m exporting with:

Export("grid.png", grd, ImageResolution -> 72*3, Background -> None);