Ink composition, ink-jet recording apparatus, ink-jet recording method, and ink container
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Solution Overview
Problem
Existing erasable inks using pH indicators in glycerin solvents suffer from poor solubility, leading to clogging and limited initial OD value, making it difficult to achieve both good solubility and erasing ability.
Innovation Solution
Incorporating a water-soluble organic solvent with an SP value of 16 or less and a blending amount of 15 wt% or more, along with a pH indicator concentration of 0.1 wt% to 0.8 wt%, to enhance solubility and erasing ability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If glycerin is used as the solvent for the pH indicator, then the ink has good erasing ability, but the pH indicator has poor solubility causing clogging and limited initial OD value
Solution Approach 1:
The patent changes the chemical composition parameters of the solvent system by introducing water-soluble organic solvents with specific SP values (16 or less, preferably 11 or more) such as polyethylene glycol, propylene glycol, and butylene glycol. This parameter change enables the pH indicator to achieve both adequate solubility (0.1-0.8 wt%) and maintains the alkaline pH (9.0-13.0) necessary for erasing ability, resolving the contradiction between solubility and erasing performance
Solution Approach 2:
The patent creates a composite solvent system combining water, glycerin, and water-soluble organic solvents with specific SP values. This composite material approach allows the ink to leverage the erasing ability of glycerin while the added water-soluble organic solvents enhance pH indicator solubility, achieving both good solubility and erasing ability simultaneously
2Illumination intensity
If the pH indicator concentration is increased to improve the initial OD value, then the OD value increases, but more sodium hydroxide is required raising the pH and making it difficult to erase the ink
Solution Approach 1:
The patent changes the solvent system parameters by incorporating water-soluble organic solvents with SP values of 16 or less. This enables the pH indicator to dissolve effectively at lower concentrations (0.1-0.8 wt%) while maintaining adequate alkalinity through controlled sodium hydroxide addition, achieving both sufficient initial OD value and erasing ability without the trade-off
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 results in an ink composition with improved solubility, initial OD value, and effective erasing ability, ensuring clear visibility on the day of printing and complete erasure within 72 hours.
Implementation Method 1
the water-soluble organic solvent includes at least one water-soluble organic solvent having a SP value of 16 or less, and a blending amount of the water-soluble organic solvent having a SP value of 16 or less is 15 wt% or more
Implementation Method 2
An erasable ink using a pH indicator which develops color in an alkaline state, for example, with phenolphthalein or the like, and erases color in a neutral state is known
Data Source
Figure 1
AI summary
A first ink composition includes: water; a water-soluble organic solvent; and a color developing agent, wherein the color developing agent contains a pH indicator, the water-soluble organic solvent includes at least one water-soluble organic solvent having a SP value of 16 or less and 11 or more, and a blending amount of the water-soluble organic solvent having a SP value of 16 or less and 11 or more is 15 wt% or more. A second ink composition includes: water; a water-soluble organic solvent; and a color developing agent, wherein the color developing agent contains a pH indicator, the water-soluble organic solvent includes at least one water-soluble organic solvent having a SP value of 16 or less, a blending amount of the water-soluble organic solvent having a SP value of 16 or less is 15 wt% or more, and the ink is a water-based ink for ink-jet recording.