Optical Element with Relief Structure for Forgery Prevention
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Solution Overview
Problem
Conventional optical elements for forgery proof face challenges in being versatile enough to function effectively both in the bank bill field, where they are attached to a transparent base material, and in the ID field, where they are attached to an opaque base material or printing layer, often requiring a metal reflection layer or highly refractive films that compromise transparency and visibility.
Innovation Solution
An optical element with a relief structure comprising two layers of different refractive indices, where light is totally reflected at one angle and transmitted at another, eliminating the need for a metal reflection layer and allowing different viewing effects on the front and rear sides, and varying reflection and transmission patterns based on observation angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a metal reflection layer or highly refractive film is used to achieve clear reflection patterns, then the reflection effect is improved, but the transparency and visibility of the optical element deteriorates
Solution Approach 1:
The patent replaces the metal reflection layer (mechanical/optical coating system) with a relief structure that utilizes total internal reflection. The relief structure consists of microscopic geometric features (such as prisms or gratings) that redirect light through geometric optics rather than requiring a reflective coating. This substitution eliminates the need for metal layers while maintaining or enhancing the reflection effect, thereby preserving transparency.
Solution Approach 2:
The patent changes the refractive index parameter by using a relief structure made of material with different refractive index than the base material. This refractive index contrast enables total internal reflection at specific angles without requiring metal coatings. By controlling the geometry and refractive index of the relief structure, the patent achieves angle-dependent reflection and transmission effects while maintaining overall transparency of the optical element.
2Device complexity
If a single-layer structure is used to simplify the optical element, then the device complexity is reduced, but the ability to provide different viewing effects on front and rear sides deteriorates
Solution Approach 1:
The patent introduces asymmetry through the relief structure's geometric configuration. The relief structure is designed with specific asymmetric features (such as tilted surfaces or non-uniform patterns) that cause light to be reflected and transmitted differently depending on the observation angle and direction. This asymmetric geometry enables the optical element to display distinct visual effects when viewed from the front versus the rear, achieving versatility without requiring multiple separate layers or components.
Solution Approach 2:
The patent adds a geometric dimension to the optical element by incorporating a three-dimensional relief structure on the surface. This relief structure creates angle-dependent optical effects by utilizing the third dimension (surface height variation) to control light propagation. The relief structure's height, slope, and pattern in the vertical dimension enable different viewing effects from front and rear sides while maintaining a essentially single-layer construction, thus achieving complexity reduction with enhanced functionality.
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 solution provides a versatile optical element that maintains transparency and visibility while preventing rear-side effects from being recognized on the front side, and offers distinct reflection and transmission patterns with an opaque base material, enhancing forgery-proof capabilities in both applications.
Implementation Method 1
electromagnetic waves incident at a preset specific angle from the first layer (2, 22) side are totally reflected due to the relief structure in the first region (4)
Implementation Method 2
electromagnetic waves incident at the specific angle from the first layer (2, 22) side are not totally reflected but transmitted or refracted due to the relief structure in the second region (5)
Data Source
Figure 1~3
Figure 4~5
Figure 6~7B
AI summary
There is provided a versatile optical element applicable both to an electrode layer required in a bank bill field and to an optical element required in an ID field. In an optical element (1) according to one embodiment of the present invention, a first layer (2) is arranged on a second layer (3) having a relief structure on a surface thereof, and a first region (4) and a second region (5) are provided. Electromagnetic waves incident at a preset specific angle from a side of the first layer (2) are totally reflected due to at least one of the relief structure in the first region (4) and a ratio of a refractive index of the second layer (3) with respect to a refractive index of the first layer (2), the electromagnetic waves incident at the specific angle from the side of the first layer (2) are not totally reflected but transmitted or refracted due to at least one of the relief structure in the second region (5) and the ratio of the refractive index of the second layer (3) with respect to the refractive index of the first layer (2), and only in case of observation performed from the specific angle on the first layer (2) side, the second region (5) has higher transparency than the first region (4), and a preset image is expressed by a transparency contrast therebetween.