Two-Part Invisible Ink Prevents Premature Activation
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Solution Overview
Problem
Existing invisible inks face issues with premature activation during manufacturing and printing, especially when produced in larger quantities, leading to clumping, foaming, and smearing, and are costly due to two-station printing requirements.
Innovation Solution
A two-part invisible ink system comprising a color developer activator and a color former leuco dye, combined with processing aids like polyvinyl alcohol, dispersants, and wetting agents, which are applied separately to prevent premature activation and improve printability on large areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If invisible ink is produced in larger quantities to cover larger areas, then the coverage area is improved, but the ink tends to clump, foam up or increase premature color development
Solution Approach 1:
The invisible ink is divided into two separate components: a leuco dye composition and an activator composition. These are applied to the substrate separately and remain stable individually, but react only when combined through frictional heat during use, eliminating clumping and premature activation while maintaining large area coverage capability
2Reliability
If the activator and leuco dye are printed separately to prevent clumping and premature activation, then the ink stability is improved, but the printing cost increases and the process becomes more complex
Solution Approach 1:
The patent combines the leuco dye and activator into a single applied layer that remains stable until frictional heat activates the color change. This single-station application eliminates the need for two separate printing stations while maintaining the stability benefits of separate component storage, reducing both complexity and cost
3Reliability
If capsules are used to encapsulate the leuco dye to prevent premature activation, then the ink stability is improved, but the capsules are prone to rupture and cause premature color development during printing, packaging and transit
Solution Approach 1:
The patent removes the capsule enclosure entirely and instead uses a chemical system where the leuco dye and activator are applied separately as stable compositions that only react when combined through frictional heat. This eliminates capsule rupture risks while maintaining prevention of premature activation
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 prevents premature color development, reduces costs, and maintains ink stability during printing and storage, allowing for efficient production and use on large substrates with reliable color change upon frictional heat activation.
Implementation Method 1
Heat generated by rubbing and/or scratching the invisible ink on the print medium activates the color former leuco dye and activator to change the color on the printing medium
Data Source
AI summary
An invisible ink, a method for preparing an invisible ink, and an invisible ink product are disclosed herein. An invisible ink comprising a first ink combined with a second ink is applied to a print medium. The first ink comprises a color developer activator without a color former leuco dye and the second ink comprises a color former leuco dye without a color developer activator. The first ink is prepared with a polyvinyl alcohol binder, dispersant/surfactant, and a wetting agent. The second ink is prepared with a polyvinyl alcohol binder, grind aid, dispersant/surfactant and defoamer. Heat generated by rubbing and/or scratching the invisible ink on the print medium activates the color former leuco dye and activator to change the color on the printing medium.