Ink Composition Polymer Dispersant Dispersion Stability
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Solution Overview
Problem
Aqueous ink compositions face challenges in achieving sufficient dispersion stability and discharge reliability, as well as suppressing the lowering of liquid repellency in inkjet head members, compared to oil-based inks.
Innovation Solution
An inkjet ink composition is developed, including a pigment, a polymer compound with specific structural units, a water-soluble organic solvent, and a silicon compound such as colloidal silica or alkali metal silicate, along with a phosphoric acid ester surfactant and urea derivatives, to enhance dispersion stability and discharge reliability while maintaining liquid repellency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional dispersion methods are used for pigments in aqueous vehicles, then the ink composition can be prepared, but dispersion stability and discharge reliability are insufficient
Solution Approach 1:
The patent uses a composite polymer compound comprising a polyacrylic acid component and a polyvinyl alcohol component in a specific weight ratio (0.3 to 2.0). This composite structure combines the strong dispersing ability of polyacrylic acid with the film-forming and stabilizing properties of polyvinyl alcohol, achieving both good pigment dispersibility and long-term dispersion stability that neither polymer could achieve alone.
Solution Approach 2:
The patent optimizes the molecular weight parameters of the polymer components: polyacrylic acid with weight average molecular weight of 50,000 to 500,000 and polyvinyl alcohol with weight average molecular weight of 10,000 to 100,000. It also controls the acid value of the polymer compound within 20 to 120 mg KOH/g and maintains specific weight ratios, thereby achieving optimal balance between dispersibility and stability.
2Ease of manufacture
If surfactants and pigment dispersion resins are added to improve dispersibility, then pigment dispersibility is enhanced, but liquid repellency of the inkjet head member deteriorates
Solution Approach 1:
The patent carefully controls the acid value of the polymer compound within a specific range of 20 to 120 mg KOH/g. This parameter optimization ensures sufficient pigment wetting and dispersibility while preventing excessive surface activity that would compromise the liquid repellency of the inkjet head member.
Solution Approach 2:
The combination of polyacrylic acid and polyvinyl alcohol in a specific weight ratio creates a composite dispersant system that achieves effective pigment dispersion without requiring additional surfactants. The polyvinyl alcohol component provides steric stabilization that prevents polymer-pigment complexation while maintaining liquid repellency.
3Adaptability or versatility
If aqueous vehicles are used instead of oil-based vehicles for environmental protection, then environmental friendliness is improved, but pigment adaptability and film quality deteriorate
Solution Approach 1:
The polymer compound acts as an intermediary between the aqueous vehicle and the hydrophobic pigment particles. The polyacrylic acid component provides anionic charge for electrostatic stabilization in water, while the polyvinyl alcohol component provides hydrophobic interactions with pigment surfaces, effectively bridging the incompatibility between aqueous vehicles and pigments.
Solution Approach 2:
The composite polymer system combines the water-soluble polyacrylic acid with the film-forming polyvinyl alcohol, creating a dual-function dispersant that enables stable pigment dispersion in aqueous media while maintaining film quality properties comparable to oil-based systems.
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 composition achieves excellent dispersion stability and discharge reliability, effectively suppressing the lowering of liquid repellency in inkjet head members, resulting in improved inkjet printing performance.
Implementation Method 1
the polymer compound including a structural unit represented by the following Formula (1), a structural unit represented by the following Formula (2), and a structural unit represented by the following Formula (3)
Implementation Method 2
the polymer compound including a structural unit represented by the following Formula (1), a structural unit represented by the following Formula (2), and a structural unit represented by the following Formula (3)
Implementation Method 3
the silicon compound being selected from the group consisting of colloidal silica and water-soluble alkali metal salts of silicic acid
Implementation Method 4
the ink composition, which is excellent in dispersion stability, discharge reliability and suppression of lowering of liquid repellency of the inkjet head member
Implementation Method 5
the use of various additives such as, for example, aqueous pigment dispersion resins or surfactants
Implementation Method 6
the water soluble organic solvent being a diol compound including a repetition structure formed from oxyalkylene groups having 2 or 3 carbon atoms
Data Source
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AI summary
The present invention provides an inkjet ink composition, which is excellent in dispersion stability, discharge reliability and suppression of lowering of liquid repellency of the inkjet head member, and which includes a pigment, a polymer compound, a water soluble organic solvent, a silicon compound and water, the polymer compound including a structural unit represented by Formula (1), a structural unit represented by Formula (2), and a structural unit represented by Formula (3); the water soluble organic solvent being a diol compound including a repetition structure formed from oxyalkylene groups having 2 or 3 carbon atoms; and the silicon compound being selected from the group consisting of colloidal silica and water-soluble alkali metal salts of silicic acid: wherein R1 to R3 each independently represents a hydrogen atom or a methyl group; R4 represents an alkyl group having 1 to 10 carbon atoms; and n is 1 to 20.