3 Answers. I'm not sure whether this should actually be just a comment, but the reason you're getting blurred, slightly jagged edges, is because you're using the line tool on a fairly low resolution image and are zoomed in. Try changing your zoom to 100% and see if the jaggedness remains.
Why does my lineart look blurry?
This is what my line art ends up as, but as you can see it is very blurry. The reason is that we are drawing on the raster layer, not the G pen. Since vector layers are resolution-free, they can be scaled. ... If you really need to worry about it, there is space, so let's draw big.
How do I reduce pixelation in Photoshop?
Remove Pixelation in Photoshop
Click on the Filter and Sharpen option. Choose Unsharp Mask to open a slider. Adjust the slider to sharpen the image until it hits a nice visual point. This will reduce the pixelation.