How Canon's Bubble Jet Printers Make Ink Droplets

Canon's 1988 patent on bubble jet printing uses a tiny heater to instantly vaporize ink, creating a bubble that pushes out a droplet of ink from the printer head.

What it covers

This patent describes how bubble jet printers work. Imagine a tiny tube, called a liquid flow path, with ink inside. At one end is an opening, the orifice, where ink droplets come out. Near this opening, but not too close, is a heating element. When the printer needs to make a dot, it sends a signal to this heater. The heater instantly gets super hot, boiling the ink right next to it. This creates a bubble. The bubble expands and pushes the ink in front of it out of the orifice, forming a droplet. Once the bubble pops, the heater cools down, and more ink flows in to fill the path, ready for the next droplet. The key is heating the ink *really* fast and only in a small spot, so it's a violent bubble, not just gentle simmering.

What it doesn't cover

• —Printing methods that use continuous streams of ink droplets.
• —Printing methods that rely on mechanical pressure or vibration to eject ink.
• —Printing methods where the heating element heats the entire ink chamber uniformly.
• —Printing methods that do not involve the formation and collapse of a vapor bubble in the ink.
• —Inkjet printers that use piezoelectric crystals to eject ink.

The clever bit

The innovation lies in the precise control of heat. Instead of just warming the ink, the patent claims a method to heat it so rapidly and locally that it causes a 'change of state' – essentially, a tiny, explosive bubble. This bubble generation is far more efficient for ejecting droplets than slower heating methods.

Why it matters

This patent is foundational for bubble jet (also known as thermal inkjet) printing technology. It enabled Canon to develop its highly successful line of inkjet printers, which brought affordable color printing to homes and offices worldwide. This technology is still a dominant force in the consumer inkjet printer market.

Real-world examples

• 1.Canon Bubble Jet printers (e.g., BJ series)
• 2.HP thermal inkjet printers
• 3.Epson thermal inkjet printers
• 4.Most consumer-grade inkjet printers