EPD stands for electrophoretic display and is the method of using electronic ink — one of Seiko’s proprietary materials — in the display of the watch.
The principal components of electronic ink are millions of tiny microcapsules, each about the diameter of a human hair. Each microcapsule contains negatively charged white particles and positively charged black particles suspended in a clear liquid.
When a negative electric field is applied, the white particles move to the top of the microcapsule, where they become visible to the user and making the surface of the screen appear white at that spot.
By reversing the process, the black particles can be induced to appear at the top of the capsule.
In addition to having a revolutionary display system, the watch receives a time signal from the world’s atomic clocks via radio wave, so that the usual accuracy of up to 15 seconds a month is improved whenever it is in range of one of the transmitters.
The time signal it receives from the atomic clocks makes the watch accurate to within one second in every 30 million years.