Chester Carlson's Original Xerography Patent

Chester Carlson's 1942 patent for xerography, the dry copying process that became the foundation for Xerox machines.

What it covers

This patent describes the fundamental process of xerography, a method for making dry copies of documents. It involves charging a surface with static electricity, exposing it to an image to create an electrostatic latent image, dusting the charged surface with a dry powder (toner), transferring that powder to paper, and then fusing the powder to make the image permanent. The core idea is using static electricity to attract toner particles to form an image, which is then heated to create a lasting copy.

What it doesn't cover

• —Does not cover wet copying processes
• —Does not cover processes that use liquid developers instead of dry powder
• —Does not cover methods that do not involve an electrostatic latent image
• —Does not cover processes that do not use heat to fuse the toner
• —Does not cover digital scanning or printing technologies

The clever bit

Carlson's genius was in combining several existing scientific principles—photoconductivity, electrostatics, and powder adhesion—into a single, practical process for image reproduction that was far simpler and faster than existing methods.

Why it matters

This patent is the bedrock of modern document copying. Chester Carlson's invention of xerography directly led to the creation of Xerox Corporation and revolutionized office document reproduction, making fast, dry copies accessible to businesses worldwide.

Real-world examples

• 1.Early Xerox copiers
• 2.Modern office document printers
• 3.Laser printers
• 4.Photocopiers