Photocurable Ink Emulsion Stability and Whiteness
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Solution Overview
Problem
Conventional photocurable inks used for forming white images on non-white substrates suffer from insufficient whiteness and storage stability due to the presence of low-boiling point solvents, which lead to porous films with minute voids and separation into layers over time.
Innovation Solution
A photocurable ink composition comprising a first liquid with a polymerizable compound and photopolymerization initiator, and a second liquid that is incompatible and forms droplets within the first liquid, containing inorganic particles adsorbed on the interface and high hydrophilicity particles in the second liquid, which vaporize to create voids and flocculated structures upon curing, enhancing whiteness and storage stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a low-boiling point solvent is used in the photocurable ink, then the cured film becomes porous with many voids that scatter light to produce white color, but the storage stability deteriorates due to separation into layers over time
Solution Approach 1:
The patent introduces an emulsifier as an intermediary substance that mediates between the incompatible first liquid (photopolymerizable compound) and second liquid (low-boiling point solvent). The emulsifier forms a stable emulsion structure where the second liquid is dispersed as fine droplets throughout the first liquid, preventing phase separation while maintaining the porous structure needed for whiteness. This resolves the contradiction by allowing the ink to maintain both its whitening function and storage stability simultaneously.
Solution Approach 2:
The patent creates a composite ink system combining two incompatible liquids (first liquid containing polymerizable compound and second liquid being low-boiling point solvent) that would normally separate. By using an emulsifier to form a stable emulsion, the patent creates a composite material that maintains the beneficial properties of both components (porosity for whiteness from the second liquid, and curability from the first liquid) while preventing the harmful separation effect.
2Illumination intensity
If the second liquid forms droplets dispersed in the first liquid, then voids are created that enhance light scattering and whiteness, but the interface between liquids creates instability leading to layer separation
Solution Approach 1:
The emulsifier acts as an intermediary at the interface between the first and second liquids, reducing interfacial tension and forming a protective layer around droplets of the second liquid. This prevents coalescence of droplets and stabilizes the emulsion structure, allowing the ink to maintain its porous whitening structure without separating into layers during storage.
3Illumination intensity
If particles are added to enhance whiteness through flocculation, then the degree of whiteness improves, but the device complexity increases due to multiple components and interfaces
Solution Approach 1:
The patent merges multiple functions into the emulsifier component: it stabilizes the emulsion, controls droplet size, prevents coalescence, and can also serve as a dispersant for particles. By combining these functions into a single key component, the patent reduces overall system complexity while achieving enhanced whiteness through controlled flocculation of particles within the stable emulsion structure.
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 ink achieves a higher degree of whiteness and improved storage stability by controlling void size and particle flocculation, preventing layer separation and maintaining physical properties over time.
Implementation Method 1
a first liquid containing a polymerizable compound and a photopolymerization initiator
Implementation Method 2
since the low-boiling point solvent is volatilized during the curing of the photocurable ink, a cured film obtained by curing the photocurable ink becomes a porous film in which many voids are present in the film
Implementation Method 3
By scattering light by these many voids, the cured film represents a white color
Data Source
AI summary
A photocurable ink containing a first liquid containing a polymerizable compound and a photopolymerization initiator, and a second liquid that is incompatible with the first liquid, in which droplets formed by the second liquid are dispersed in the first liquid, wherein the photocurable ink contains first particles and second particles having higher hydrophilicity than that of the first particles, wherein the first particles are adsorbed on an interface between the first liquid and the second liquid, and the second particles are present in the second liquid.