Dr. Franco Moia Profile

Dr. Franco Moia

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Proceedings Article | 3 June 2004 Paper

New color-shifting security devices

Franco Moia

Proceedings Volume 5310, (2004) https://doi.org/10.1117/12.530544

KEYWORDS: Polarizers, Inspection, Information security, Liquid crystals, Neodymium, Eye, Image visualization, Visualization, Reflectivity, Polarization

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The unbroken global increase of forgery and counterfeiting of valuable documents and products steadily requires improved types of optical security devices. Hence, the "security world" is actively seeking for new features which meet high security standards, look attractively and allow easy recognition. One special smart security device created by ROLIC's technology represents a cholesteric device combined with a phase image. On tilting, such devices reveal strong color shifts which are clearly visible to the naked eye. The additional latent image is invisible under normal lighting conditions but can be revealed to human eyes by means of a simple, commercially available linear sheet polarizer. Based on our earlier work, first published in 1981, we now have developed phase change guest-host devices combined with dye-doped cholesteric material for application in new security features. ROLIC has developed sophisticated material systems of cross-linkable cholesteric liquid crystals and suitable cross-linkable dyes which allow to create outstanding cholesteric color-shifting effects not only on light absorbing dark backgrounds but also on bright or even white backgrounds preserving the circularly polarizing state. The new security devices combine unambiguously 1^st and 2^nd level inspection features and show brilliant colors on black as well as on white substrates. On tilting, the security devices exhibit remarkable color shifts while the integrated hidden images can be revealed by use of a sheet polarizer. Furthermore, due to its very thin material layers, even demanding applications, such as on banknotes can be considered.

Proceedings Article | 19 April 2002 Paper

New colored optical security elements using Rolic's LPP/LCP technology: devices for first- to third-level inspection

Franco Moia

Proceedings Volume 4677, (2002) https://doi.org/10.1117/12.462710

KEYWORDS: Information security, Polarizers, Inspection, Computer security, Reflectivity, Security technologies, Wave plates, Optical components, Liquid crystals, Data hiding

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With linear photo-polymerization (LPP) ROLIC has invented a photo-patternable technology enabling to align not only conventional liquid crystals but also liquid crystals polymers (LCP). ROLIC's optical security device technology derives from its LPP/LCP technology. LPP/LCP security devices are created by structured photo-alignment of an LPP layer through phot-masks, thus generating a high resolution, photo-patterned aligning layer which carries the aligning information of the image to be created. The subsequent LCP layer transforms the aligning information into an optical phase image with low and/or very high information content, such as invisible photographic pictures. The building block capability of the LPP/LCP technology allows the manufacturing of cholesteric and non-cholesteric LPP/LCP devices which cover 1st and/or 2nd level applications. Apart from black/white security devices colored information zones can be integrated. Moreover, we have developed an LPP/LCP security device which covers all three- 1st, 2nd and 3rd- inspection levels in one and the same authentication device: besides a color shift by tilting the device (1st level) and the detection of normally hidden information by use of a simple sheet polarizer (2nd level) the new device contains encrypted hidden information which can be visualized only by superimposing an LPP/LCP inspection tool (key) for decryption (3rd level). This optical key is also based on the LPP/LCP technology and is itself a 3rd level security device.

Proceedings Article | 7 April 2000 Paper

Optical LPP/LCP devices: a new generation of optical security elements

Franco Moia, Hubert Seiberle, Martin Schadt

Proceedings Volume 3973, (2000) https://doi.org/10.1117/12.382188

KEYWORDS: Information security, Polarizers, Wave plates, Optical components, Liquid crystals, Reflectivity, Glasses, Visualization, Polarization, Security technologies

Read Abstract +

With linear photo polymerization (LPP) ROLIC has developed a new photo-patternable technology which enables to align not only conventional liquid crystals bu also LCP. ROLICs optical security device technology derives from its LPP/LCP technology. LPP/LCP security devices are crated by structured photo-alignment of an LPP layer through photo- masks, thus generating a high resolution, photo-patterned aligning layer which carries the aligning information of the image to be created and which is machine readable. The subsequent LCP layer transforms the aligning information into an optical phase image. Among a large number of possible LPP/LCP optical effects that lead to LPP/LCP security devices - all of them with distinct optical appearance - we will concentrate on the following LPP/LCP security elements: Reflective and transmissive LPP/LCP security devices for 2nd level inspection applications. LPP/LCP images are invisible when viewed with the naked eye but becomes visible when viewed through a polarizer. Rotation of the polarizer leads to contrast inversion: i.e. the image changes from 'positive' to 'negative' which is an additional unique security feature. Other types of LPP/LCP security devices are based on cholesteric films. We will present 2nd level cholesteric LPP/LCP devices which can be sued as overlays and superimposed on printed information which remains visible through the overlay.

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