Electrokinetic pixels with biprimary inks for color displays and color-temperature-tunable smart windows

Abstract

We report on the advanced implementation of the biprimary color system in applications where subtractive color is performed inside a single pixel to alter the magnitude and color of reflection (electronic paper displays) or the optical transmission and color temperature (smart windows). A novel device structure can switch between four states: clear, black, either of two complementary colors from RGB and CMY sets, and also mixed states between one of these four states. The device structure utilizes an electrokinetic pixel structure, which combines the spectral performance of in-plane electrophoretic devices with the improved switching speeds of vertical electrophoresis. The electrophoretic dispersions are dual-particle dual-colored and are controlled using two traditional planar electrokinetic electrodes on the front and back substrates, along with a third electrode conveniently located at the perimeter of each unit cell. Demonstrated performance includes contrast ratios reaching ~10∶1, reflectance of ~62%, and transparency of ~75%. For electronic paper displays, these results provide a pathway to double the reflective performance compared to the traditional RGBW color-filter approach. For smart windows, the technology provides not only control of shade (transmission) but also provides complete control over color temperature. Furthermore, this three-electrode device can be roll-to-roll fabricated without need for any alignment steps, requiring only a single micro-replication step followed by self-aligned contact printing of the third electrode.

A Systematic Review and Classification of Glazing Technologies for Building Façades

“…Electrokinetic pixel glazing technology is a polarised particle technology, such as LCD technology, that aims to modulate the colour and temperature of the visible light passing through electrochromic glazing. According to [118], by controlling the movement of coloured particles via an applied voltage, it is possible to modulate separately the transmission and colour of the light entering the glazing.…”

A Review of Smart and Responsive Building Technologies and their Classifications

“…To that end, an electrophoretic dispersion of dualparticles of 2 biprimary complementary colours are considered and three properly located electrodes are used to control this dispersion moving the coloured particles. This displacement leads to different states of the window from the neutral clear state to the neutral dark one (Mukherjee et al 2015).…”

36‐1: Variable Transmission Electrophoretic Films

“…Several methods have been demonstrated to concentrate such particles. For example, in-plane concentrator electrodes may be provided on one side of an electrophoretic fluid while on the opposite side is a transparent, conductive electrode covering the whole area of the device [15] [16]. An alternative to concentrator electrodes is an embossed pattern of microwells that cover only a small portion of the display area.…”