Full-color, crisp, vivid images have become essential across all visual applications, while energy conservation and carbon reduction are now global trends. Through a series of image tests, we will delve into the characteristics of Spectra 6 and ChLCD e-paper technologies, helping readers understand their strengths and weaknesses and choose the most suitable color e-paper for their applications.

How Spectra 6 works?

Spectra 6 features E Ink's ACeP (Advanced Color ePaper) technology, which consists of microcups filled with four ink particles: red, blue, yellow, and white. By applying different voltages, these ink particles can be shifted to generate six standard colors: black, white, red, yellow, blue, green.

Spectra 6 contains micro cups of red, blue, yellow, and white ink.

When the electronic paper display needs to present colors beyond the six specified, it requires precise blending of these six colors to simulate similar hues when viewed from a distance.

Cholesteric liquid crystal (ChLCD) e-paper has three layers of displays that reflect red, green, and blue respectively. The electric field alters the rotation of the liquid crystals that is bistable between the two states:

• The planar state has the liquid crystal particles lined up uniformly to reflect specific wavelengths of light, to form unique colors.
• The focal conic state lines up the liquid crystal particles in a way to let light pass through, displaying the colors underneath.

Altering the ChLCD particles on different layers to fully reflect light (white), partial reflection (gray), or no reflection (black).

By independently adjusting the states of the three RGB liquid crystal layers, ChLCD can perfectly reproduce more than 16 million colors, creating a rich color image comparable to LCD.

Differences in color palettes

Using this comprehensive color palette as an example, Spectra 6 exhibits high saturation in yellow but shows gaps in green tones with poor magenta and cyan. In contrast, ChLCD offers a more comprehensive color performance across all colors.

Left) original image, middle) Spectra 6 lacks cyan, magenta, and green, right) ChLCD with a complete range of colors.

Differences in gradients

A gradient image clearly showcases the performance of different color e-paper technologies across the full-color gamut. In the case of Spectra 6, cyan appears as light blue, and magenta appears as purple. On the other hand, ChLCD delivers more accurate color representation with proper gradient in each color band.

Left) original image, middle) Spectra 6 displays cyan as light blue and magenta as purple, right) ChLCD demonstrates more accurate gradient performance.

Human portraits

Human portraits and faces are common in advertising billboards, so the fine image quality, smooth transitions between highlights and shadows, and realistic skin tone reproduction are essential for accurate representation. In human portraits, Spectra 6 shows clear edges around shadows, which make the person seem like they are wearing a mask. While ChLCD offers a smoother shadow transition, with better skin texture, eyebrows, and more defined hair strands.

Left) original image, middle) Spectra 6 shows a sharp edge around shadows on the face with a grainy texture on the skin, right) ChLCD presents finer details in skin texture and hair.

Food images

Color, aroma, and taste are the fundamental pursuits of gourmet food, and when the physical experience is not accessible, the importance of color becomes even more evident.
Taking Spectra 6 as an example, the saturation and gloss of the dragon fruit's skin are significantly reduced. In contrast, ChLCD displays a more vibrant color for the dragon fruit's skin and a clearer, cleaner appearance for the kiwi's flesh.

Left) original image, middle) as seen in Spectra 6, the saturation and gloss of the dragon fruits are noticeably reduced, right) ChLCD displays a more vibrant color for the dragon fruits.

Fashion advertising

In billboard applications, a wider color gamut better meets customer expectations. Taking a lipstick advertisement as an example, Spectra 6 shows a significant difference in the color representation of the lipstick and lips compared to the original image, while ChLCD's performance in magenta is closer to the original.

Left) original image, middle) Spectra 6 shows gray lips and lipstick instead of pink, right) ChLCD is much closer to the original.

Overall, from the comparisons above, we can see that ChLCD offers finer detail, higher saturation, and brightness. Its color rendering is closer to the original image, better meeting market demands.

Outdoor full-color e-paper application

Outdoor displays face harsher conditions like extreme temperatures, humidity, and direct sunlight. Wide-temperature liquid crystals are essential for ensuring traditional displays work reliably in all weather.

Because ChLCD is based on liquid crystal technology, it can withstand outdoor temperature variations. It is the only color e-paper on the market with an operating temperature range of -20°C to 70°C. Even in direct sunlight, ChLCD can maintain vivid colors and is not affected by extreme heat or cold.

When combined with an IP56 or higher, UV-resistant enclosure, IRIS Optronics' ChLCD e-paper can withstand wind, rain, and other outdoor elements. Whether it's a freezing ski resort, a hot and humid beach, or a sunny golf course, the cholesteric liquid crystal display can deliver vibrant colors.

Speed differences between Spectra 6 and ChLCD

Apart from color performance, another key metric for color e-paper is refresh speed. The more color ink microcapsules the EPD needs to control, the more complex the control method and the longer the update time. The 6-color Spectra 6 screen below requires around 15 seconds to refresh an image.