Ink Set Viscosity Control via Solvent Ratios and Lithium Content
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Solution Overview
Problem
Inkjet recording methods face issues with ink stains on non-recording surfaces due to viscosity increases when lithium salts in ink compositions are replaced by potassium salts during dummy jetting, leading to impaired image quality and appearance.
Innovation Solution
An ink set comprising yellow, magenta, cyan, and black ink compositions with specific solvent ratios and lithium content, where each ink contains compounds represented by certain formulas and their salts, along with solvents A to D, to maintain low viscosity and prevent ink stains on recording media.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dummy jetting is performed to clear the jetting nozzle, then the jetting nozzle is cleaned and jetting stability is improved, but ink compositions of multiple colors are mixed and stored in the ink disposal unit causing viscosity increase and ink stains on non-recording surfaces
Solution Approach 1:
The patent extracts and removes the harmful mixed ink from the ink disposal unit through a flushing operation. A flushing ink is jetted into the ink disposal unit to displace and remove the mixed ink that caused viscosity increase and staining, thereby eliminating the harmful effect while preserving the beneficial dummy jetting function.
Solution Approach 2:
The patent changes the composition parameters of the flushing ink by controlling the content of specific solvents (solvent A: 5-20 mass%, solvent B: 70-85 mass%, solvent C: 5-20 mass%) to create an ink formulation that effectively reduces viscosity and prevents staining when used for flushing the ink disposal unit.
2Stability of the object's composition
If lithium salts are used in ink compositions, then solubility and precipitation resistance are improved, but viscosity increases when replaced by potassium salts during mixing
Solution Approach 1:
The patent changes the solvent composition parameters to compensate for viscosity increases. By adjusting the ratios of solvent A (0.5-5.0 mass%), solvent B (10.0-40.0 mass%), and solvent C (5.0-20.0 mass%), the ink maintains low viscosity even when lithium salts are replaced by potassium salts during mixing in the ink disposal unit.
Solution Approach 2:
The patent uses a composite solvent system combining multiple solvents (A, B, C) with different properties. This composite solvent composition works synergistically to maintain solubility and prevent precipitation while controlling viscosity, allowing flexible replacement of lithium salts with potassium salts.
3Reliability
If multiple colors of inks are dummy jetted and mixed in the ink disposal unit, then the jetting nozzle is cleared, but the mixed ink accumulates and contacts recording media causing ink stains
Solution Approach 1:
The patent performs a preliminary flushing action by jetting flushing ink into the ink disposal unit before normal recording operations. This preliminary action removes the mixed ink that would otherwise accumulate and stain recording media, preventing the harmful effect in advance.
Solution Approach 2:
The patent introduces a separate flushing operation that quickly removes harmful mixed ink from the ink disposal unit. This rushing through of flushing ink displaces and removes the problematic mixed ink, preventing it from contacting recording media.
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 set effectively suppresses ink stains on non-recording surfaces by maintaining low viscosity and ensuring high lithium content, thereby enhancing image quality and appearance.
Implementation Method 1
each of the yellow ink composition, the magenta ink composition, the cyan ink composition, and the black ink composition contains, with respect to a total mass of each ink composition, 0.5% by mass to 5.0% by mass of a solvent A containing no nitrogen atom and having a solubility parameter value, i.e. an SP value of 22 MPa 1/2
Data Source
AI summary
One embodiment of the present invention provides an ink set including at least an ink including a compound represented by Formula (Y-1) or (Y-2) or the like, an ink including a compound represented by Formula (M) or (MM) or the like, an ink including a compound represented by Formula (C) or the like, and an ink including a compound represented by Formula (B) or the like, in which each ink composition contains, with respect to the total mass of each ink composition, 0.5% to 5.0% of an N-free solvent A having an SP value of 22 to 26 MPa1/2, 0.1% to 5.0% of an N-containing solvent B having an SP value of 24 to 29 MPa1/2, 10% to 50% of an N-free solvent C having an SP value of 29 to 31 MPa1/2, 5% to 30% of an N-free solvent D having an SP value of 32 to 34 MPa1/2, and 30% to 60% of water, and a ratio of the total mass of Li with respect to the total mass of alkali metals included in the entire ink provided by mixing each ink composition at an equal mass ratio is 70% by mass or more, and an application thereof.