Welcome to SolidWorks forums Peter.
Check if your video card is approved one and also the drivers are up to date. If this is OK then try making a PDF out of the SolidWorks and check the quality in there. Also place a view in drawing and do a save as JPG from drawing and check.
You might also find this post helpful for your future reference.
I had the same issue. Also when printing/print preview.
I am using SW2012 with Nvidia Quadro K1000M. Upgrading to the latest approved SW2014 driver (307.83) solved the issue.
Better to go For screen shot or PrtScn options..