Select "None" under two grid group section for Major and Minor on both X Grid and Y Grid tab to remove the grid lines seen in image. This will make pure white or black background. Currently Major grid has "Line" as selected option. Thus you see the lines.
Select "None" under two grid group section for Major and Minor on both X Grid and Y Grid tab to remove the grid lines seen in image. This will make pure white or black background. Currently Major grid has "Line" as selected option. Thus you see the lines.