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Manufacture of Pressure-Sensitive Products
Published in István Benedek, Mikhail M. Feldstein, Technology of Pressure-Sensitive Adhesives and Products, 2008
Thermal printing, which uses heat to color the face stock, comprises direct thermal printing and transfer thermal printing. Direct thermal (thermosensitive or thermochemical) printing applies a heat-sensitive printing material, which undergoes a color change when heated. This method of printing was developed in Japan, for facsimile paper, in the early 1970s. For instance, a direct thermal printable label may have a five-layer construction. The paper carrier is coated with a top layer that includes a heat-sensitive ink embedded in a lacquer. Some labels also have a protective overlayer. For direct thermal printing, special paper is required. Common organic direct thermal printable papers include a colorless leuco dye and an acidic color developer. These are coated and held onto the surface of the paper with a water-soluble binder. During printing, the two components melt together and react chemically to form the color. To limit this image to the heated area, inorganic fillers (e.g., calcium carbonate, clay) are used. The problem of image stability (protection against chemicals) is solved by applying a top coat as a transparent film-forming layer. It is also possible to apply a barrier coat to the underside of the paper to prevent adhesive or plasticizer migration from the opposite side. These papers are classified as non-top-coated (nonsmudgeproof) and top-coated (smudgeproof) papers.
An optically efficient full-color reflective display with an electrochromic device and color production units
Published in Journal of Information Display, 2019
Ik Jang Ko, Jin Hwan Park, Gyeong Woo Kim, Raju Lampande, Jang Hyuk Kwon
The schematic of full-color reflective displays consisting of a reflective ECD and color display units (CF and TCECF) is shown in Figure 1. Recently, we reported a reflective ECD [25] with a titanium-dioxide-(TiO2)-based white reflector and simultaneously utilized a high-performance black ECD to display the basic optical information (black and white) using reflected ambient light. This reflective ECD showed high reflectance (58.5%) in the white state owing to the excellent reflection property of the TiO2 white reflector, which reflects most of the ambient light (95.5%) in the visible wavelength range (400–700 nm) with negligible optical loss (4.5%). Besides, the transmittance and optical density of the black ECD in the bleached (0.0 V) and colored (1.7 V) states were around 83.2% and 1.5, respectively. Particularly, in the colored state, two very broad and high-optical-density peaks with increasing applied voltage appeared at 435 and 585 nm. Those two peaks were almost included in the visible light spectrum due to the different chemical state of leuco dye. As shown in Figure 2, leuco dye can reversibly exhibit both the bleached and colored states according to the chemical status of the lactone ring, which can be determined from the reaction of leuco dye with the acid species, such as a proton donor compound. In addition, the reflective ECD displayed 3.5 and 43.4 s coloring and bleaching response times, respectively at the driving voltages of 1.7 and 0 V. Likewise, the diffuse reflectance of the reflective ECD in the white and black states was stable (about 10% optical change) after 10,000 driving cycles, and it showed a total power consumption of only 10 mW.