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Citizen Develops ‘Eco-Drive One,’ the Thinnest Watch in the World

Takafumi Uno




Watch technology continues to evolve, with advancements like GPS (Global Positioning System) functions being added, and the ability to connect to smart phones to set the correct time.


Amid the emergence of “smart watches,” which can measure the wearer’s heart rate, comes the “Ultimate Watch” from Citizen. Due for release this autumn, it offers the most simplified function and design possible.


The “Eco-Drive One” is the world’s thinnest, analog light-powered watch with a movement measuring 1 millimeter thick and a case thickness of 2.98 millimeters. The slimline body, which turns conventional watchmaking on its head, involves delicate technology which underlies an ambition to deliver “world-first” developments.


“Let’s reconsider the essence of watches, and attempt to create a pared-down version, a simple and beautifully thin watch.” This was the directive that company president Toshio Tokura gave, jumpstarting the development of the Eco-Drive One in the summer of 2014.


Citizen produced the world’s first solar-powered, analog watch for sale in 1976. In 1995, Citizen released the “Eco-Drive” watch, which garnered worldwide popularity as an environmentally friendly watch.


The Eco-Drive One was developed as the 40th anniversary model of the analog light-powered watch. As such, enthusiasm in the development and planning divisions was markedly high. Their aim was “minimalistic beauty.”


“When numerous functions are added to a watch, it inevitably becomes larger and thicker. Conversely, we thought we would build a comfortable, functional, and well-honed watch,” said Kazuya Imamura of the development department’s design section.



When the Citizen “Stiletto” was launched in 2014, it had the world’s thinnest movement, with a thickness of 1.91 millimeters. The Eco-Drive One has managed to almost halve that.


At first glance, it seems quite unremarkable. However, it is without clock numbers or a second hand. When worn, it is comfortable and light. It is so thin that it slips easily under sleeve cuffs when you are not checking the time, and it never gets in the way.


However, it was not an easy task to fit all 85 integral working components into the 1-millimeter-thick movement. Eighty-one of the components had to be fundamentally redesigned.


One of the most important components is the rotor, the so-called heart of the watch, which combines the permanent magnet and the gears, and moves the watch hands.


The original thickness of the rotor was 1.47 millimeters, which meant it protruded from the allocated 1 millimeter thickness. To reduce this to 0.96 millimeters, they did away with the metal “seat,” which usually joins the magnet and gears, and instead developed an innovative laser-welding technique.


Moreover, given that no rechargeable batteries under 1 millimeter thick existed, Citizen undertook joint development with Hitachi Maxell to reduce the battery size to 0.9 millimeters. In addition, special measures were undertaken to construct the coil necessary to move the watch hands—it has a 0.3-millimeter-thick core, bound by wire which is 0.017 millimeters thick.


The developers were not satisfied with increased thinness, since, as Imamura said, “the demerits of being thin began to arise, such as being susceptible to water pressure and warping when wet.”


As such, a durable exterior was created using new, superior-strength materials, Binderless Cemented Carbide and Cermet, for the bezel (which holds the front glass) and the watch back. Thus, a unique watch, combining both thinness and strength, was born.


For a human, 40 years old is middle-aged, but it is still an age where one can tackle various new challenges. The Eco-Drive will also continue to grow.



Eco-Drive One Citizen has developed the world’s thinnest analog light-powered watch. Eco-Drive One is the culmination of a desire to realize a 1-millimeter-thick movement. When fully charged, it will run for one year, even in the absence of light. The suggested retail price (before tax), for the three stainless steel band models is \300,000, and \700,000 for the limited edition (800 pieces), crocodile leather strap model.


Citizen Watch Company Kamekichi Yamazaki, founder of Tanaka Kikinzoku Jewlery K.K., founded the Shokosha Watch Research Institute in 1918. In 1924, they began selling pocket watches under the name “Citizen,” in the hope of being “loved by the people.” In 1930, the company name was taken from the brand, and “Citizen Watch” was established. In 2007, the company name was changed to “Citizen Holdings,” but was later changed back to “Citizen Watch” in October 2016. Citizen has developed a range of brands, including, “Exceed,” “Atessa,” and “xC.” It has total sales of \3.482 trillion (consolidated, quarter ended March 2016), with 17,046 employees.


Takafumi Uno is a staff writer of the Sankei Shimbun, economic news department.



(Click here for the original article in Japanese.)


Takafumi Uno is a staff writer of the Sankei Shimbun Economic news department.

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