It’s actually called carbon paper.
Carbon paper was invented in the early 19th century, and the inventor was Wedgwood in England. At that time, he was running a literary shop in London. Wedgwood often wrote letters in pencil to his regular customers, introducing him to several new stationery items in the store. The contents of these letters were almost the same. He wrote them mechanically, a little bored. "Can I write two or three letters at the same time?" Looking at the traces of writing on the last piece of paper left on the last piece of paper, this idea suddenly came to Wedgwood's mind. It didn't seem difficult to realize this idea, and Wedgwood quickly figured out the method: soak a piece of tissue paper in blue ink, and then sandwich it between two pieces of blotting paper and let it dry. When writing, a copy can be obtained by lining it under regular paper. In 1806, Wedgwood received a patent for his "Device for Copying Letters and Documents." When Wedgwood's invention came out, British commercial activities were already very developed, and carbon paper was of great use. Seeing that his invention was so popular, Wedgwood simply set up a factory to produce this special paper. Later, the French switched to the method of infiltrating glycerin and pine smoke into the paper to make carbon paper. Around 1815, the Germans made another innovation, using hot glycerin and dye extracted from coal tar, finely grinding and researching, and coating it on tough tissue paper to make new carbon paper. Later, people added wax to the coating of this carbon paper to reduce the viscosity. This is the carbon paper we commonly use today.