A multiple-electrode-type electronic paper film can implement a single color and control the transparency, as it has multiple electrodes in one cell. Therefore, it can be used as a transparent display. In this paper, we explain the structure and driving method of a transparent electronic paper display, and then propose a control method of transmittance. Subsequently, we verify the theory by measuring the transmittance via experiment. Thus, by changing the manner of applying the voltage to three lower electrodes and one upper electrode, transmittance in eight cases could be realized. It was confirmed that the transmittance derived from the experiment could be controlled from a minimum of 6.75% to a maximum of 71.18%.

A multielectrode electronic paper film capable of expressing a single-color image was fabricated by injecting color electronic ink into an electronic paper panel; on the basis of its reflective or transparent properties, it is possible to control the expression of six single-color images and their transmittance. In this study, a single-color image was represented by driving a multielectrode electronic paper film; color coordinates were measured. The six capable single colors were yellowish pink (0.444, 0.354), white (0.355, 0.352), black (0.241, 0.241), orange (0.514, 0.360), reddish orange (0.606, 0.338), and reddish purple (0.469, 0.145). Color particles used in this paper were black and white, by which six colors are accomplished, but more single-color images can be combined by using cyan, magenta, and yellow particles.

An electronic paper display was fabricated by injecting electronic ink, including white and black particles coated by positive and negative charge control agents (CCA), respectively, into closed cells surrounded by micro-barriers. These two types of charged, colored particles are easily damaged or their charging value can be changed by the injection process; therefore, the electrical and optical properties of the image panel fabricated by the injection method were estimated in this study. The active particle-loading method, proposed as a new electronic ink injection process, was applied, and the electro-optical properties of the resulting three-electrode-type e-paper image panel were analyzed. The reflection rate of the white image-panel fabricated with our new injection method was 24.7%, while that of the same panel fabricated with a previously reported injection method was 19.8%. In addition, the response time was improved by about five times compared to those reported in other publications.

We fabricate a single particle-microcapsule type electronic paper using electrophoresis, which is different with a reported dual particle-microcapsule type and of which electro-optical researches are not reported. So we analyzed a basic properties, such as reflectivity, response time, and driving voltage. Our display panels having various cell-gaps of 30 ㎛, 34 ㎛, 38 ㎛, 42 ㎛, and 46 ㎛ are inspected. As a results, a driving voltage is defined to 10 V and desirable cell-gap is 30 ㎛ or 34 ㎛. Considering a mechanical strength, the optimum cell-gap is 34 ㎛ for the single particle type electronic paper.