Heat-Sensitive Paper Imaging Liquid for Rapid Low-Temperature Drying
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Solution Overview
Problem
Existing image forming methods on heat-sensitive paper using water-based ink face challenges such as prolonged drying times due to hydrophobic coat layers and potential discoloration from reactions between leuco dye and color developer when heated, which can lead to ink adherence issues and discoloration.
Innovation Solution
A liquid composition with specific solubility parameters for organic solvents and resin particles is used, where the first organic solvent has a higher content than the second, ensuring the ink penetrates and dries quickly while minimizing leuco dye solubility, combined with controlled heating processes to prevent discoloration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If water-based ink is used on heat-sensitive paper, then the ink can be applied to the coat layer, but the drying time is prolonged due to the hydrophobic nature of the coat layer
Solution Approach 1:
The patent changes the chemical composition parameters of the ink by incorporating specific organic solvents (first organic solvent with solubility parameter 12.0-20.0 and second organic solvent with solubility parameter 9.0-12.0) in controlled ratios. This parameter modification enables the ink to penetrate the hydrophobic coat layer more effectively and dry faster, resolving the contradiction between adequate coat layer coverage and prolonged drying time.
2Productivity
If heating is applied to dry the ink quickly, then the drying speed increases, but discoloration occurs due to reaction between leuco dye and color developer
Solution Approach 1:
The patent modifies the chemical parameters of the ink system by selecting organic solvents with specific solubility parameters that prevent leuco dye dissolution. The first organic solvent (solubility parameter 12.0-20.0) and second organic solvent (solubility parameter 9.0-12.0) are formulated in specific ratios to create an environment where the leuco dye remains insoluble even at elevated drying temperatures, thus preventing discoloration while enabling faster drying.
Solution Approach 2:
The organic solvents act as intermediary substances that mediate between the need for rapid drying and the prevention of discoloration. By carefully selecting solvents with appropriate solubility parameters and controlling their ratios, the system enables heat drying without causing leuco dye to dissolve and react with the color developer, thus resolving the contradiction between drying speed and discoloration prevention.
3Quantity of substance
If the solubility parameter of the organic solvent is close to that of the leuco dye, then the leuco dye dissolves in the liquid, but this causes reaction with color developer and discoloration
Solution Approach 1:
The patent strategically selects organic solvents whose solubility parameters (first: 12.0-20.0, second: 9.0-12.0) are deliberately kept away from the leuco dye's solubility parameter range (8.0-9.0). This parameter selection ensures the leuco dye remains insoluble in the ink formulation, preventing unwanted reactions with the color developer and subsequent discoloration, while still achieving adequate ink flow and drying performance.
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 method effectively suppresses discoloration and accelerates drying on heat-sensitive paper, reducing ink adherence and ensuring high-quality image formation without discoloration.
Implementation Method 1
the solubility parameter of the second organic solvent in the liquid has a value close to the solubility parameter of the polymer in the coat layer. Due to this, the liquid applied to the coat layer can easily penetrate into the coat layer by the effect of the second organic solvent
Implementation Method 2
the liquid comprises the first organic solvent having the solubility parameter significantly different from the solubility parameter of the leuco dye, and the content of the first organic solvent is greater than that of the second organic solvent. Due to this, the leuco dye can be suppressed from dissolving in the liquid by the effect of the first organic solvent
Implementation Method 3
a drying process of drying the medium with the liquid applied thereon at a second temperature which is lower than the first temperature
Data Source
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AI summary
An image forming method may comprise: feeding a medium (2) including a heat-sensitive layer (L) and a coat layer (M) on the heat-sensitive layer (L), in which the heat-sensitive layer (L) may comprise a color developer (P) and a leuco dye (Q) which reacts with the developer at a first temperature, and the coat layer (M) may comprise a polymer; applying liquid onto the coat layer (M) of the medium, in which the liquid may comprises first and second organic solvents; and drying the medium at a second temperature lower than the first temperature. A solubility parameter of the leuco dye may be 8.0 or more and 9.0 or less. A solubility parameter of the polymer may be 11.0 or less. A solubility parameter of the first organic solvent may be 12.0 or more and 20.0 or less. A solubility parameter of the second organic solvent may be 9.0 or more and less than 12.0. A content of the first organic solvent to a total liquid amount may be higher than that of the second organic solvent to the total liquid amount. A sum of the content of the first organic solvent to the total liquid amount and the content of the second organic solvent to the total liquid amount may be less than 25 weight %.