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3 February 2009 Security applications of liquid crystal film with plural latent images
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Liquid crystal (LC) cells with plural latent images have been proposed for security devices. The photo crosslinkable polymer surface is irradiated with unpolarized UV light through the photo-mask and subsequently rubbed. The LC aligns parallel and perpendicular to the rubbing direction on the UV irradiated and unirradiated surfaces, respectively. A guest host mode LC cell is prepared using our alignment patterned substrates. Double-faced optical writing is also successfully demonstrated in the guest host mode LC cell by exposing from both sides of the cell with unpolarized UV light. The LC cell is uniformly colored under the natural ambient light. Two latent images can individually be visualized when a polarizer is replaced in front of and behind the cell. The third latent image is obtained as a result of logical operation for two patterned images when the LC cell is set between the polarizer and analyzer. We can see three domains, that is, transparent, colored and black domains. Each part shows the result of the logic operation of two images, that is, "AND", "NOT" and "EOR". The alignment patterned LC cell is also utilized as a key cell to visualize the latent information in the LC cell.
© (2009) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Rumiko Yamaguchi "Security applications of liquid crystal film with plural latent images", Proc. SPIE 7232, Emerging Liquid Crystal Technologies IV, 72320Q (3 February 2009);

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