Why can some printed invoices be underlined with black nails?

Reason: The invoice is carbonless carbon paper. Carbonless copy paper is a kind of colorless copy paper, which has the functions of direct copying and direct color development. Its coloring is mainly: under the action of external force, the force-sensitive pigment and oil solution in the microcapsule overflow and contact with the colorant to produce dyeing reaction, thus playing the role of replication. Mainly used for multiple bills, bills, continuous financial bills, general business financial bills, etc.

Advantages:

(1) There is no need for "carbon paper" when copying, so it is convenient and time-saving to write directly. 2-6 pages of carbon paper and 2- 10 pages of electronic printing can greatly improve work efficiency and meet the needs of modernization.

(2) The handwriting of the copy is clear and vivid, does not fade, and can prevent alteration and imitation.

(3) Don't pollute your fingers, clothes and other stationery paper, and keep it clean.

(4) Various colors, easy to identify and process.

(5) Excellent paper quality, smooth surface, stronger than 28g colored paper, not easy to be damaged and rich in printing colors.

(6) It contains no harmful raw materials and peculiar smell, is safe and reliable, and the developed pictures and texts can be stored for more than 15 years.