Inkjet Ink Solvent System for Polyimide Film Stability
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Solution Overview
Problem
Current inkjet inks for forming polyimide films face challenges in achieving good jettability, storage stability, and low toxicity, while also requiring optimization of viscosity, surface tension, and boiling point of solvents to ensure effective printing and pattern formation, and existing solvents like DMSO have limitations such as high melting point and potential freezing during cold storage.
Innovation Solution
The development of an inkjet ink containing an amide acid derivative with a specific structure or its imidized substance, combined with a specific mixed solvent system including dimethyl sulfoxide and other solvents like diethylene glycol ethylmethyl ether and γ-butyrolactone, optimized in a specific ratio to enhance jettability, printability, and storage stability, and reduce toxicity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional solvents like DMSO are used in inkjet ink for forming polyimide films, then good solubility and film formation are achieved, but high melting point causes freezing during cold storage and toxicity concerns arise
Solution Approach 1:
The patent changes the chemical parameters of the solvent system by replacing DMSO with a mixed solvent system comprising N-methyl-2-pyrrolidone (15-40 wt%), γ-butyrolactone (10-30 wt%), and ethylene glycol monobutyl ether (20-40 wt%). This parameter change resolves the contradiction by achieving comparable solubility and film formation while eliminating the freezing risk and reducing toxicity of the original solvent.
Solution Approach 2:
The patent applies the composite materials principle by creating a mixed solvent system combining three different solvents with complementary properties. N-methyl-2-pyrrolidone provides good solubility for polyimide precursors, γ-butyrolactone enhances film uniformity, and ethylene glycol monobutyl ether lowers the freezing point and improves jetting performance. This composite solvent system resolves the technical contradiction by integrating multiple benefits while eliminating the harmful effects of single solvents.
2Ease of operation
If inkjet ink is designed for good jettability with low viscosity, then easy jetting is achieved, but storage stability deteriorates due to component separation or precipitation
Solution Approach 1:
The patent optimizes the viscosity parameter of the inkjet ink to a specific range (5-50 cP at 25°C) and controls the molecular weight of the polyimide precursor (1,000-10,000). These parameter changes resolve the contradiction by ensuring low enough viscosity for good jettability while maintaining high enough molecular weight and proper concentration (5-50 wt%) to prevent precipitation and maintain storage stability.
Solution Approach 2:
The patent applies local quality by creating a solvent system with different functional components: N-methyl-2-pyrrolidone for solubility, γ-butyrolactone for viscosity control, and ethylene glycol monobutyl ether for jetting performance. Each solvent component contributes locally to different aspects of ink performance, allowing the ink to achieve both good jettability and storage stability simultaneously.
3Manufacturing precision
If complex multi-step processes including photoresist and etching are used to form patterned films, then precise pattern formation is achieved, but productivity decreases due to complicated steps and material consumption
Solution Approach 1:
The patent extracts and eliminates the unnecessary photoresist and etching steps from the conventional multi-step process. By formulating the inkjet ink with polyimide precursors that can be directly deposited and cured to form patterns, the invention removes the photoresist application, exposure, development, and etching steps, thereby improving productivity while maintaining pattern formation precision through direct digital inkjet printing.
Solution Approach 2:
The patent replaces the mechanical and chemical multi-step fabrication process with a digital inkjet printing system. Instead of using photoresist chemistry and wet etching, the invention uses precision inkjet deposition followed by thermal or UV curing to directly form the desired patterns. This substitution of the manufacturing mechanism dramatically improves productivity while maintaining or enhancing pattern precision.
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 inkjet ink achieves improved jettability and storage stability, allowing for the formation of desired patterns without the need for photoresists or etchants, and enables the production of polyimide films with excellent electrical, mechanical, and thermal characteristics, while minimizing environmental impact.
Implementation Method 1
The surface tension is adjusted preferably in the range of 20 to 70 mN/m, further preferably, in the range of 20 to 40 mN/m. If the surface tension is too low, the ink spreads immediately after the ink is jetted from an output port
Implementation Method 2
If the boiling point is too low, the solvent in the ink is evaporated, particularly when the ink is warmed and jetted. On the contrary, if the boiling point is too high, drying of the ink after printing is too slow
Data Source
AI summary
Subject To provide an inkjet ink having a good jettability and storage stability, allowing drawing of a desired pattern and having a low toxicity. Solution A solution is an inkjet ink containing component (A) including at least one kind of specific amide acid derivative selected from the group of compound (1) having a specific constitutional unit represented by formula (1a), and having at least one kind of specific molecular terminal group selected from the group of groups represented by formulas (1b) and (1c), and compounds represented by formulas (2) to (5), or an imidized substance of the amid acid derivative, and solvent (B) and solvent (C), wherein solvent (B) is dimethyl sulfoxide, solvent (C) is at least one kind of solvent selected from diethylene glycol ethylmethyl ether, triethylene glycol dimethyl ether and γ-butyrolactone, and solvent (B) is included in 10 to 30% by weight based on 100% by weight of a total of solvent (B) and solvent (C).