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There are currently two leading e-paper display technologies: electrochromic displays (ECD) and electrophoretic displays (EPD). 

Electrochromic e-paper display

Electrochromic displays work by using an electric field to change the color or opacity of a material, such as a metal oxide or organic polymer. When an electric current is applied, the material undergoes a chemical reaction that alters its optical properties, causing it to change color or become transparent. Ynvisible is the leading supplier of printed electrochromic e-paper displays.

Electrophoretic e-paper display

EPDs use microcapsules filled with electrically charged colored particles (typically black and white) suspended in a clear fluid. When an electric field is applied to the microcapsules, the particles move to the top or bottom of the capsule, creating a visible image. E ink™ is the primary provider of electrophoretic displays.

The terms E ink™ displays, EPD, e-paper, electronic paper, and electrophoretic displays are commonly used interchangeably, but it is essential to recognize that the electrophoretic display is part of the wider e-paper display category, and E ink™ is just one of the players in this field.

What do they have in common?

Both are reflective display technologies designed for applications with ultra-low power requirements that only need occasional display changes. Typical use cases are electronic shelf labels and eReaders, but also emerging applications such as dynamic CVC on credit cards or smart labels for pharmaceutical containers. 

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How do they differ?

As mentioned, electrochromic and electrophoretic displays share a few common attributes, but they are actually more dissimilar than one may think. The key differentiators are the layouts (graphics/segments), driving, color availability, and bistability, as summarized in the table below:

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Electrophoretic technology targets markets with more challenging demands for high resolution, colors, and bistability, whereas electrochromic technology is more suitable for basic, low resolution, low information density interfaces. To put this into an example, the electrophoretic is commonly used for high-resolution, high information density, and multi-color electronic shelf labels, and the electrochromic is used for monochrome price-only electronic shelf labels with less information density.

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The aforementioned differences are reflected in the price point of the two technologies.

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The electrochromic displays are significantly more cost-effective than the electrophoretic technology. Another key differentiator is the cost of making custom solutions.

The printed electrochromic e-paper technology is highly suitable for cost-effective customizations thanks to the flexibility and low tooling costs associated with the screen-printing processes used for manufacturing.

The electrophoretic technology typically comes in standard formats, and large quantities (or minimum order quantities) are required to justify custom solutions.

One of the critical cost drivers is that the electrophoretic technology is more complex to produce due to the thin-film transistor matrix backplane, which is not needed for direct-driven electrochromic technology.

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There are implications when it comes to power budget, display driving, and electronics required to operate the two display technologies.

Key differences are the power consumption when it comes to display changes (dynamic power) and to keep the display active (static power), operating voltage, and display driver requirements. These differences are summarized in the table below:

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Other distinct attributes include thickness, flexibility, and substrate. The electrochromic display provided by Ynvisible is printed on a thin and flexible plastic substrate. No rigid backplane is needed, which makes the final display solution only 300µm thin, fully bendable, and effectively shatterproof. The electrophoretic option is typically glass-based and includes a backplane, which makes it thicker, non-bendable, and more prone to crack or shatter.

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Conclusions

To conclude, both technologies are promising emerging technologies and should always be considered when looking for ultra-low power displays.

Electrophoretic is preferred when full bistability, colors, and/or high information density are needed. Typically, electrophoretic is used in existing markets and applications, replacing more power-consuming display technologies. 

Electrochromic is preferred for cost-sensitive and custom applications, typically with low information density. This display technology is also preferred for emerging applications, such as wound care, medical skin patches, and various smart labels, where thinness, flexibility, and sustainability are strict requirements. Furthermore, electrochromic displays have uniquely low voltage and can change color with as low as ±1V, which is a benefit for most electrical circuits, especially when designing systems with sensors or voltage-generating components which directly could trigger a display change.