Security Element Micromirror Segmentation for Demetallization
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Solution Overview
Problem
The existing demetallization processes for security elements with micromirror structures face challenges with increasing embossing depth, leading to incomplete wetting of wash ink, metallization defects, and unattractive gray haze due to register fluctuations and porous structures.
Innovation Solution
The solution involves splitting the relief area into an inner and edge area with different micromirror sizes, where the inner area has larger dimensions for brilliance and the edge area has smaller dimensions for complete wetting and removal, ensuring reliable demetallization and transparency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the embossing depth is increased to improve relief display quality, then the brilliance of micromirrors is improved, but the wash ink cannot completely wet the mirror structures leading to metallization defects
Solution Approach 1:
The patent segments the micromirror structures into two distinct groups based on their vertical dimension: micromirrors with a vertical dimension of 2-20 μm that should be metallized, and micromirrors with a vertical dimension of 0.5-2 μm that should be demetallized. This segmentation allows the wash ink to selectively wet only the smaller micromirrors, achieving reliable demetallization while preserving the brilliance of the larger micromirrors through differential wetting behavior.
Solution Approach 2:
The patent applies local quality by creating micromirrors with different vertical dimensions in different regions. The larger micromirrors (2-20 μm) provide high brilliance for the relief display, while the smaller micromirrors (0.5-2 μm) are specifically designed to be wetted by the wash ink for demetallization. This local differentiation of micromirror sizes enables simultaneous achievement of optical quality and reliable demetallization.
2Illumination intensity
If the micromirror size is increased to improve brilliance, then the relief display quality is improved, but the wash ink registration accuracy becomes insufficient leading to gray haze
Solution Approach 1:
The patent segments the micromirror population into two size classes: larger micromirrors (2-20 μm vertical dimension) for brilliance and smaller micromirrors (0.5-2 μm vertical dimension) for demetallization. This segmentation ensures that even with registration variations of +/- 0.3 mm, the wash ink reliably targets only the smaller micromirrors, preventing gray haze while preserving the brilliance of the larger micromirrors.
Solution Approach 2:
The patent implements local quality by varying the vertical dimension of micromirrors based on their functional requirement. Larger micromirrors are positioned in regions requiring high brilliance, while smaller micromirrors are positioned in regions requiring demetallization. This local differentiation compensates for registration inaccuracies by ensuring that the wash ink's larger footprint always encompasses the smaller micromirrors.
3Shape
If the embossing depth is increased to improve relief rendering, then the three-dimensional effect is improved, but metal-free areas show gray haze due to porous structures
Solution Approach 1:
The patent segments the micromirror structures into two vertical dimension groups to eliminate gray haze: larger micromirrors (2-20 μm) that maintain high brilliance without requiring demetallization, and smaller micromirrors (0.5-2 μm) that are completely wetted by the wash ink to ensure thorough removal of metallization. This segmentation prevents the gray haze problem by ensuring complete demetallization of the smaller structures while preserving the optical quality of the larger ones.
Solution Approach 2:
The patent applies local quality by creating regions with different micromirror dimensions optimized for their specific function. The smaller micromirrors in demetallized areas have sufficient vertical dimension (0.5-2 μm) to provide relief rendering but are small enough to be completely wetted by the wash ink, eliminating gray haze. The larger micromirrors in metallized areas provide high brilliance without requiring demetallization.
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
This approach ensures a brilliant relief display with reliable removal of the reflective coating, preventing metallization defects and achieving transparent, haze-free demetallized surfaces.
Implementation Method 1
the printing ink forms a porous, raised ink layer after drying
Implementation Method 2
The ink application and the overlying metallic cover layer can then be removed by washing with a suitable solvent
Data Source
Figure 1~2(b)
Figure 3(a)~4
Figure 5(a)~6
AI summary
The invention relates to a security element (12) for protecting valuable objects, comprising a substrate (20) having a surface region (22) which is provided in regions with a reflective coating (42), the surface extension of which surface region defines an x-y plane and a z-axis perpendicular thereto, and which surface region consists of a relief region (24) formed by a plurality of stamped elements (30, 32), the size of which is determined by means of a lateral dimension in the x-y plane and a vertical dimension in the z-direction, and of an outer region (26) that lies outside the relief region (24). According to the invention, - the relief region (24) has an inner region (34), in which the stamped elements (30) are completely reflectively coated, and an edge region (36), which lies between the inner region (34) and the outer region (26) and in which some of the stamped elements (32) are reflectively coated and the remainder of the stamped elements (32) are not coated, - the outer region (26) is completely uncoated, and - the average lateral dimension of the stamped elements in the edge region (36) is less than 90% of the average lateral dimension of the stamped elements (30) in the inner region (34).