Most of the printers, photocopiers, and multifunction devices so common in offices nowadays use a printing method that relies on toner, ink in powdered form. This printing method enables high-speed, high-quality printing on almost any kind of paper.
Toner is made up of fine particles about 5–10 micrometers in diameter, milled from a thermoplastic binder resin into which colorant (pigment) is micro-dispersed. Heat causes the binder resin to melt and adhere to the paper, resulting in durable output that resists friction and moisture. From the standpoint of energy conservation and printing speed, there are clear benefits to a binder that fuses and fixes at a relatively low temperature, with minimal heating. At the same time, the toner must be able to remain in a stable powder form within the printing environment (up to 50°C).
Through a process of polymer design that took account of such properties as affinity for paper, Kao developed the world's first polyester toner binder featuring both low-temperature fixing and powder stability, seemingly incompatible properties. Later, we turned our attention to a highly thermoresponsive crystalline material, dispersing nanoparticles (10–100 nanometers) of the substance throughout the toner to further reduce the environmental burden.
Kao continues to pursue development of toner and toner binder technology oriented to reducing the environmental burden in various dimensions through such strategies as the use of plant-based materials, lower energy consumption in manufacturing, reduced toner consumption, and easy de-inking.