Inkjet Ink Set Using Sol-Gel Phase Transition for Dot Separation and Gloss
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Solution Overview
Problem
Conventional UV-curable inkjet systems suffer from poor image quality due to dot combination during high-speed recording and inability to achieve sufficient glossiness, as inks with gelling agents either prevent dot combination but introduce surface irregularities or fail to provide adequate gloss.
Innovation Solution
An inkjet ink set comprising a color ink and a clear ink, both undergoing temperature-induced sol-gel phase transition, where the color ink has a higher viscosity at 25°C to prevent dot combination and the clear ink has a lower viscosity to ensure leveling, ensuring high image quality and glossiness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a gelling agent is added to UV-curable inkjet ink to prevent combining of neighboring dots, then dot combination is prevented, but fine irregularities are produced on the surface and glossiness is insufficient
Solution Approach 1:
The invention divides the ink system into two separate inks: a color ink containing a gelling agent for dot separation, and a clear ink without gelling agent for surface smoothing. This segmentation allows each ink to perform its specific function independently, resolving the contradiction between preventing dot combination and maintaining surface smoothness.
Solution Approach 2:
The clear ink acts as an intermediary substance applied after the color ink. It mediates between the irregular surface created by the color ink and the final smooth, glossy surface requirement. The clear ink fills in the fine irregularities and provides the desired surface quality without interfering with the dot separation function of the color ink.
2Shape
If clear ink is applied to smooth the surface and the recording medium is heated to make the clear ink surface uniform, then surface smoothness is improved, but additional processing steps and energy consumption are required
Solution Approach 1:
The invention extracts the heating step from the necessary processing sequence by formulating the clear ink with appropriately selected viscosity and composition. The clear ink achieves surface smoothing through its inherent properties and the natural gelation process, eliminating the need for additional heating equipment and processing steps while still achieving the desired surface smoothness.
3Productivity
If high-speed recording is performed using line recording head or high speed serial recording, then productivity is improved, but neighboring dots combine and image quality deteriorates
Solution Approach 1:
The color ink is formulated with a gelling agent that causes rapid gelation upon deposition. This preliminary action of gelation occurs before the ink can spread or combine with neighboring dots, even during high-speed recording. The rapid gelation locks the dots in place, preserving image quality while allowing high productivity.
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 set effectively prevents dot combination while achieving high-resolution images with enhanced glossiness and surface smoothness, addressing the limitations of conventional UV-curable inkjet systems.
Implementation Method 1
a color ink that undergoes temperature-induced sol-gel phase transition
Implementation Method 2
a radically photocurable compound, a photopolymerization initiator
Implementation Method 3
attaching droplets of the color ink in the inkjet ink set according to the invention to a recording medium by discharging the droplets from an inkjet recording head
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
An inkjet ink set comprising: a color ink including a photocurable compound, a photopolymerization initiator, a gelling agent, and a colorant, the color ink undergoing a sol-gel phase transition depending on the temperature; and a clear ink including a photocurable compound, a photopolymerization initiator, and a gelling agent, the clear ink undergoing a sol-gel phase transition depending on the temperature. The viscosity (η) (CL) of the clear ink at 25°C is less than 1/2 the viscosity (η) (CO) of the color ink at 25°C, and the viscosity (η) (CL) of the clear ink is 1 × 103 mPa·s or greater. Provided is an inkjet ink set by which a printed image offering both high image quality and surface gloss can be formed.