Security Foil Negative Writing via Gas-Generating Ink
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Solution Overview
Problem
Existing methods for producing security films with negative writing struggle to achieve clear and clean contours, especially in thick coatings or layer structures that are difficult to penetrate with solvents, and often result in poor congruency across multiple layers.
Innovation Solution
A method using a printing ink that selectively destroys the coating through contact with a washing liquid, generating gas or swelling to exert force on the coating, allowing for precise removal of coatings, including those made of multiple layers, without requiring significant permeability to the solvent.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional printing inks are used with washing processes, then thin coatings can be removed, but thick coatings or multi-layer structures cannot be effectively penetrated by solvents resulting in poor washing results
Solution Approach 1:
The printing ink utilizes phase transition through gas generation (e.g., CO2 from acid-carbonate reactions) or foam formation when contacted by washing liquid. This phase change creates internal pressure that mechanically breaks up the coating structure, enabling solvent penetration into thick and multi-layer coatings that would otherwise be impermeable, while maintaining sharp contour definition
Solution Approach 2:
The invention changes the physical-chemical parameters of the printing ink by incorporating reactive components (acids, carbonates, blowing agents) that transform the ink from a passive material to an active coating-destroying agent. This parameter change enables the ink to generate gas or foam upon contact with washing liquid, creating forces sufficient to break up thick coating structures
2Manufacturing precision
If multiple coating layers are applied to achieve desired security features, then congruency across layers becomes difficult to achieve, but this is essential for clear character definition
Solution Approach 1:
The invention merges the functions of multiple coating layers into a single removable structure by applying all layers over the printing ink. The gas-generating ink acts as a unified removal trigger that simultaneously breaks up and removes all overlying layers in congruent patterns, eliminating registration errors that would occur with sequential layer processing
3Ease of manufacture
If opaque metal layers are used to simulate precious metals, then cost is reduced, but solvent penetration becomes difficult resulting in poor washing results
Solution Approach 1:
The gas-generating printing ink creates phase transition effects that produce mechanical forces capable of breaking up dense opaque metal layers. The generated gas bubbles create internal pressure that fractures the metal coating structure, allowing washing liquid to penetrate and dissolve the printing ink binder, thereby removing the metal layers with sharp contour definition despite their opacity and density
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
Enables the formation of security films with sharp, clearly defined negative writing that is congruent across all layers, even in thick or complex coating structures, enhancing visibility and security features.
Implementation Method 1
a gas is generated in the printing ink when it comes into contact with the washing liquid
Implementation Method 2
a process takes place which results in the printing ink exerting a force on the coating by the printing ink
Implementation Method 3
the printing ink and the covering layer above it are removed by washing out with a liquid
Data Source
Figure 1~4
Figure 5~8
Figure 9~12
AI summary
The method for producing a safety foil for a valuable document e.g. check, comprises printing a side of a substrate with a printing ink (4) in the form of characters to be produced, applying a coating on the printed side of the substrate, and removing the printing ink and the area of the coating lying over the printing ink by washing with an aqueous washing liquid, so that slots are formed in the form of characters in the coating. The safety foil has visually recognizable characters in the transmitted light and in the reflected light. The printing ink contains a filler and a binding agent. The method for producing a safety foil for a valuable document e.g. check, comprises printing a side of a substrate with a printing ink (4) in the form of characters to be produced, applying a coating on the printed side of the substrate, and removing the printing ink and the area of the coating lying over the printing ink by washing with an aqueous washing liquid, so that slots are formed in the form of characters in the coating. The safety foil has visually recognizable characters in the transmitted light and in the reflected light. The printing ink contains a filler, a binding agent and a reactive component and/or a precursor of a reactive component, which causes a process during contacting with the washing liquid and/or during irradiation or heating, where the process leads to crack the area of the coating during contacting and/or irradiation or heating. The reactive component is the filler. The reactive component and/or the precursor of the reactive component is a first component (5') of a two-component gassing system that consists of the first component and a second component (5''). The first component is contained in the printing ink and the second component is contained in the washing liquid. The first- and/or the second component are a mixture of reaction agent. The two-component gassing system produces carbon dioxide. The first component is a catonic photo-initiator that adjusts an acid during irradiation with a pre-determined wavelength. A portion of the first component or the second component is 10-20 wt.% at the printing ink. The components are used in stoichiometric quantities related to the functional groups. The reactive component of the printing ink that causes the process during irradiation or heating is a foaming agent or swelling agent. The printing ink contains the first component, the swelling agent and/or foaming agent. The printing ink has 15-30 wt.% of filler, 5-15 wt.% of binding agent, 50-80 wt.% of water, and 50-80 wt.% of water-free solvent. The coating is a metal layer (7) or metal containing layer. A further layer is applied on to the coating over the side of the substrate printed with the printing ink. A magnetic ink layer, interference pigment layer, liquid crystal layer, a metal layer and a chromatic color for the preservation of precious metal optics are applied as the further layer. The area of the coating and the further layers is jointly removed by washing register during the removal of printing ink. The coating and the further layers are applied in a total thickness of 1 nm up to 15 mu m. The printing of the substrate takes place in an intaglio printing process. The washing of the printing ink is supported by mechanical means. Independent claims are included for: (1) safety foil for attaching at or for partially bringing in a valuable document such as bank note, a check or an identification card; (2) valuable document; and (3) a process for manufacturing a valuable document.