Optically Variable Security Device Using Color-Shifting Layers
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Solution Overview
Problem
Existing security devices utilizing liquid crystal materials for optically variable features face limitations in color range and complexity in production, particularly when using pigmented inks or single-layer films, which are prone to degradation in color purity and sharpness, and are challenging to replicate the angular-dependent color shifts effectively.
Innovation Solution
A security device comprising multiple layers of color-shifting materials with a light control layer having a microprismatic structure that modifies the angle of reflected light, allowing for enhanced color shifts and increased color range by altering the viewing angle, and can be applied in a registered pattern to reveal latent images or patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If pigmented liquid crystal ink is used to apply liquid crystal material in the form of a design, then it can be applied using conventional printing processes, but the color purity, brightness and sharpness of the observed colour and colourshift are significantly degraded
Solution Approach 1:
The invention divides the liquid crystal material into two separate components: a liquid crystal film providing uniform alignment and high color purity, and a pigmented ink layer applied in registered patterns to create designs. This segmentation allows each component to fulfill its optimal function - the film ensures optical quality while the ink enables conventional printing application methods
Solution Approach 2:
The invention creates a composite structure combining a liquid crystal film with pigmented ink layers. The film provides the optical basis with high color purity, while the ink layers add design elements and can reveal latent images when viewed at different angles. This composite approach merges the advantages of both materials while mitigating their individual disadvantages
2Device complexity
If a single layer of liquid crystal film is used, then the production process is simplified, but the range of colours available is limited to substantially pure spectral colours with fixed colourshift direction
Solution Approach 1:
The invention adds a temporal dimension to color display by utilizing angular-dependent viewing. Multiple ink layers with different color characteristics are applied in registered patterns, and the full color range is revealed when the document is viewed at different angles. This transforms a static single-color film into a dynamic multi-color system
Solution Approach 2:
The pigmented ink layers are pre-applied in registered patterns on the liquid crystal film. These ink layers contain color information that is initially obscured at normal viewing angles but is revealed when the document is tilted, allowing the system to present multiple colors sequentially as the viewing angle changes
3Adaptability or versatility
If additional layers are incorporated to customise the visual appearance, then the security device can be personalised, but the production complexity increases
Solution Approach 1:
The liquid crystal film serves multiple functions simultaneously: it provides the base colorshift effect, acts as a carrier for the pigmented ink layers, and enables angular-dependent viewing. The pigmented ink layers also serve dual purposes by creating visible designs at normal angles and revealing latent images at tilted angles, reducing the need for separate customization 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 enhances the color-shifting effects, making it easier to authenticate and more difficult to counterfeit, while maintaining aesthetic appeal and durability, by providing a wider range of colors and kinematic effects viewable across various angles.
Implementation Method 1
a light control layer having a surface structure which modifies the angle of reflected light, such that light reflected by the colourshifting layers is seen at different viewing angles
Implementation Method 2
certain liquid crystal materials exhibit a difference in colour when viewed in transmission and reflection, as well as an angularly dependent coloured reflection
Implementation Method 3
the light control layer having a surface structure which modifies the angle of reflected light
Data Source
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AI summary
The present invention relates to improvements in security devices that can be used in varying shapes and sizes for various authenticating or security applications, and in particular to an optically variable security device utilising colourshift materials. The security device comprising a first and a second layer of a colourshifting material at least partially overlying each other and each having different colourshifting properties and, at least partially applied over an exposed surface of one of the colourshifting layers, a light control layer having a surface structure which modifies the angle of reflected light, such that light reflected by the colourshifting layers is seen at different viewing angles.