Diagnosis
The anti-glare coating on the IPS panel is porous. Dry dusting or using a dirty cloth pushes oil and debris into the coating, creating smears.
How to Fix It
Use a clean, lint-free microfiber cloth designed for glasses or lenses. Lightly dampen a section of the cloth with distilled water only. Wipe the screen gently in a single direction. Immediately dry the area with a dry section of the cloth using straight, overlapping strokes.
If That Didn't Work
For stubborn smudges, use a 50/50 mix of distilled white vinegar and distilled water. Apply sparingly to the cloth, not directly to the screen. Test on a small corner first. The acetic acid can break down oils without damaging the coating.
Heads Up
Never use window cleaners, alcohol, ammonia, or abrasive cloths. They will permanently damage the anti-glare coating, leaving shiny, blotchy patches. Never spray liquid directly onto the screen, as it can seep into the panel edges.