Security Element with Liquid-Crystal Motif and Embossing Varnish
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Solution Overview
Problem
Existing security elements with liquid-crystalline materials face challenges in producing high-resolution, thin layers with optimal contrast and releasability, often requiring alignment-promoting conditions and specific layers, which can lead to poor optical properties and difficulty in reproducing authentic motifs.
Innovation Solution
A security element comprising a first embossing varnish layer with alignment structures of different orientations, a nematic liquid-crystalline material layer aligned homogeneously, and a second embossing varnish layer with a microoptical relief structure and reflection-increasing coating, allowing polarization-dependent optical effects to be visible with auxiliary means, such as polarizers, while avoiding regions that hinder alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a nematic liquid-crystalline material layer is applied thinly to achieve high resolution, then manufacturing precision is improved, but the layer thickness becomes insufficient to form an optimal λ/4 layer for light, worsening optical contrast
Solution Approach 1:
An alignment layer is introduced as an intermediary between the carrier film and the nematic liquid-crystalline material layer. This alignment layer serves dual functions: it enables proper molecular orientation of the liquid crystal and simultaneously increases the effective optical path length, allowing thin physical layers to achieve the required λ/4 optical thickness for optimal contrast
Solution Approach 2:
The refractive index of the alignment layer is specifically selected to be between the ordinary and extraordinary refractive indices of the liquid crystal material. This parameter change in the intermediate layer compensates for the reduced physical thickness, maintaining the necessary optical path length difference for λ/4 operation and preserving optical contrast
2Ease of manufacture
If solvent-based liquid-crystal formulations are printed to achieve complete coverage, then manufacturing ease is improved, but the wet film thickness becomes too great causing running or flowing, worsening manufacturing precision
Solution Approach 1:
The alignment layer is applied and prepared in advance before the liquid-crystal formulation is printed. This preliminary action creates a surface that promotes uniform spreading and prevents excessive flow, allowing the printed formulation to maintain pattern definition while achieving complete coverage
Solution Approach 2:
The alignment layer acts as a mediator between the printed liquid-crystal formulation and the carrier film. It controls the wetting and spreading behavior of the formulation, preventing uncontrolled running or flowing while ensuring complete coverage of the substrate surface
3Manufacturing precision
If alignment-promoting conditions are introduced to improve liquid crystal alignment, then manufacturing precision is improved, but the device complexity increases due to additional layers and processing steps
Solution Approach 1:
The alignment layer is designed to perform multiple functions simultaneously: it provides alignment promotion for the liquid crystal molecules, serves as an optical intermediary to achieve λ/4 optical path length in thin layers, and acts as an adhesion promoter between the carrier film and liquid-crystal formulation. This multi-functionality reduces the need for separate specialized layers
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables the creation of secure, high-resolution, and visually appealing security features with enhanced protection against forgery, as the different alignment structures and microoptical relief structures provide distinct motifs visible through polarizers, improving contrast and visibility without relying solely on print accuracy.
Implementation Method 1
the viewing angle-dependent color impression and/or light-polarizing effect of liquid crystals
Implementation Method 2
the nematic liquid-crystalline material has been printed onto a carrier film in a pattern
Implementation Method 3
a desired embossed structure, for example a diffraction structure, is embossed into the embossing varnish layer
Data Source
AI summary
A security element for safeguarding of articles of value, has a motif layer based on a liquid-crystalline material intended and destined to form a latent motif. The security element includes a first embossing varnish layer disposed on a carrier film, a partial motif layer based on a nematic liquid-crystalline material, and a single- or multilayer second embossing varnish layer present over the full area. The first embossing varnish layer has been provided with an embossment having at least two regions with alignment structures of different orientation for formation of a second latent motif. The motif layer, in the form of a first latent motif, is disposed in regions directly atop the first embossing varnish layer and in an overlapping arrangement with the regions that form the second latent motif.