Liquid crystal displays are now used in digital watches, smartphones, televisions and a host of other products. Nearly 50 years ago, Seiko Epson Corporation (Suwa Seikosha at the time but referred to hereafter as Epson) was among the first companies to see the promise of practical applications for liquid crystal technology and began research and development. This R&D effort culminated in the release of the world's first digital wristwatch equipped with a six-digit field-effect liquid crystal display (FE LCD).
Epson succeeded in developing the world's first analog quartz watch, in 1969. While analog watches, with hands that tick off the time, had their supporters, the global tide was shifting toward digital watches, which display numbers, and digital watch research and development gained momentum around the world. Epson rode this tide and began developing fully electronic digital watches while concurrently developing quartz watches.
The difference between an analog watch and a fully electronic digital watch is that the latter lacks a mechanical drive mechanism. Everything up to the vibration of the crystal unit that counts the time and the electronic circuit that shapes the emitted waves is the same in both types of watch. However, fully electronic watches do not have a stepping motor beyond the electronic circuit as analog quartz watches do. Instead, they are designed to send an electric signal directly to the liquid crystal display panel to display the time.
The world's first digital wristwatch was announced in 1970 by an American company. However, that watch used an LED display, which left room for improvement in terms of readability and power consumption. Epson therefore set out to develop a different type of digital watch.
The photo shows the internal structure of 06LC.
Epson turned its attention to liquid crystals, which were beginning to attract attention as display elements that could be electronically controlled. Epson initially considered dynamic scattering mode (DSM) liquid crystal as a potential display candidate but eventually concluded that customers would benefit more from an FE LCD because of its high visibility and low power consumption. Epson launched R&D on FE LCDs in 1968 and took on a series of challenging technical issues, including the synthesis and encapsulation of liquid crystal, electrode structures, operating temperature range, panel display contrast conditions, and volume production.
An LCD is produced by encapsulating liquid crystal molecules between a pair of glass substrates equipped with a polarizing filter and electrodes. Text and images are displayed by controlling the switching of voltages and controlling the amount of light transmitted through the polarizers. In an FE LCD, alignment layers are disposed on either side of the liquid crystal layer. The alignment layers have grooves that run in a fixed direction. The liquid crystal molecules sandwiched between these layers align themselves along the grooves. So, when one of the alignment layers is rotated 90 degrees from the other, the liquid crystal molecules twist 90 degrees. Light that travels along the liquid crystal molecules will also twist 90 degrees so that it passes through the gaps in the second polarizer. Liquid crystal molecules also realign when a voltage is applied. Under a voltage, the molecules align vertically so that the light travels straight, without twisting, until it reaches the second polarizer, which blocks it.
Epson used these features of FE LCDs to independently develop the ideal display for digital watches. Feeding this development were the efficient, compact, and precision technologies that Epson nurtured in the manufacture and development of mechanical watches. These included technologies and skills for precision processing, shrinking the geometries of electronic circuits, and accomplishing volume production.
In October 1973, Epson (at that time, Suwa Seikosha) released the fully electronic Seiko Quartz LC V.F.A. 06LC, a digital watch that displayed the time on an FE LCD rather than on a dial with hands. The LCD display showed six digits, two each for the hour, minutes, and seconds.
The watch looks digital, but the source of the time-keeping vibrations is a crystal oscillator like that used in quartz watches. The watch thus maintained excellent accuracy and, thanks to reduced power consumption, could run for two years on the same battery. In addition, users could individually adjust the hour and minutes with the simple push of a button.
In addition to the LCD, the 06LC was equipped with a lamp. Customers around the world raved about the contrast of the display and the clarity of the numbers. As a result, LCDs became the display of choice for digital watches developed after the 06LC.
Meanwhile, Epson was conducting parallel development work on applications other than digital watches. Before using them in contemporary products such as 3LCD projectors and smart glasses, Epson was using LCDs in products such as TV watches (1982), mobile phones (1993), and pocket-sized color TVs (1984).
Epson's FE liquid crystal technology has been developed and become widely adopted as twisted-nematic (TN) liquid crystal. It is used by Epson and many other electronics manufacturers as a core technology for liquid crystal displays and many other products.
In 2019, the technology related to the development of the world's first six-digit LCD digital wristwatch was recognized along with subsequent achievements by the National Museum of Nature and Science as one of the Essential Historical Materials for Science and Technology.