Diffraction Grating Printing via Photopolymerization
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Solution Overview
Problem
Existing methods for creating sub-microscopic or holographic diffraction gratings on substrates, such as documents and packaging, are costly and inefficient due to the need for separate operations involving high pressure and heat, which can distort the grating patterns and require significant metal deposition, leading to reduced manufacturing speed and quality issues.
Innovation Solution
A method involving the direct deposition of metallic ink onto a substrate with a curable compound, followed by forming a diffraction grating on the ink, allowing for in-line printing and registration of the grating directly onto the substrate, using a conventional printing press with diffraction grating forming means, enabling high productivity and low-cost production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If high pressure and heat are used to emboss the diffraction grating, then the grating can be formed on the substrate, but the grating patterns become distorted and manufacturing quality deteriorates
Solution Approach 1:
The patent replaces the mechanical embossing system (heated cylinders applying pressure) with a photochemical system. A photopolymer coating is applied to the substrate and exposed to ultraviolet light through a master plate containing the diffraction grating pattern. The light causes the photopolymer to cure and form the grating pattern without mechanical contact, eliminating distortion caused by pressure and heat.
Solution Approach 2:
The patent changes the fundamental parameters of the formation process from thermal-mechanical (high temperature and pressure) to photchemical (ultraviolet light exposure). This parameter change allows the grating to be formed through a non-contact optical process rather than a contact mechanical process, preserving pattern fidelity.
2Illumination intensity
If significant metal deposition is applied to provide mirror-like luster, then the visibility of the image is improved, but the manufacturing cost and complexity increase
Solution Approach 1:
The patent uses metallic inks containing reflective pigments (such as aluminum, silver, or gold particles) that are applied through conventional printing methods. These pigments provide the desired mirror-like luster and light reflection properties without requiring vacuum metal deposition equipment. The metallic effect is achieved through the optical properties of the pigment particles rather than a continuous metal layer.
Solution Approach 2:
The patent replaces the complex vacuum metal deposition system with a conventional printing system that applies metallic ink. This substitution uses a well-established, simpler printing technology to achieve the same visual effect of light reflection and image visibility.
3Manufacturing precision
If separate operations are used for creating diffraction gratings and transferring them to substrates, then the gratings can be formed with high precision, but the manufacturing speed and productivity decrease
Solution Approach 1:
The patent combines multiple operations into a single integrated process. The diffraction grating is formed directly on the substrate in one step by exposing the photopolymer-coated substrate to ultraviolet light through a master plate. This eliminates the need for separate grating formation and transfer operations, as the grating is created in situ on the final substrate.
Solution Approach 2:
The substrate is pre-coated with photopolymer material before the grating formation step. This preliminary action prepares the substrate to receive the diffraction pattern directly, enabling the subsequent single-step exposure process to create the grating permanently on the substrate without requiring later transfer operations.
4Ease of manufacture
If heated embossing members are used to form the diffraction grating, then the grating can be embossed into the substrate, but the manufacturing cost and process complexity increase
Solution Approach 1:
The patent replaces the thermal-mechanical embossing equipment (heated cylinders, pressure systems) with a photchemical exposure system. The diffraction grating is formed by exposing a photopolymer coating to ultraviolet light through a master plate, eliminating the need for heated embossing machinery and associated complex temperature and pressure control systems.
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 allows for the efficient and cost-effective transfer of sub-microscopic or holographic diffraction gratings onto substrates with improved manufacturing speed and quality, enabling the gratings to be visible from both surfaces and enhancing security features on products like identification documents and packaging.
Implementation Method 1
The substrate is supplied with a coating of photopolymer, exposed to ultraviolet light through a diffraction grating master plate and subsequently cured
Implementation Method 2
Security printing using a diffraction grating... use diffraction grating patterns and images which include sub-microscopic, holographic and other forms of diffraction gratings... Three-dimensional light diffracting patterns such as a hologram
Data Source
AI summary
There is provided an apparatus and a method of printing a diffraction grating. In particular, the present invention relates to diffraction gratings applied to a substrate (1), such as a hologram.