Need Suggestion for Keeping a Scanner Clean

We have a scanner that I have to manually clean 2 or 3 times a week. The reason it gets dirty is because we print invoices on 3-part paper:

1. Once part stays with the company and gets scanned
2. Once part goes to the customer
3. Once part stays with the warehouse.

The scanner is getting dirty because the properties of the 3-part paper that make it print to all three layers ends up doing the same thing to the rollers on my scanner.

For example the red is the build up and the green is the recently cleaned. As you can see below the ink that beads to the other parts of the 3 part paper also gets beaded to my scanner:

This is the build up: from the two rollers in green:

Any ideas about what I can do to prevent?