UV-Curable Inkjet Ink Droplet Control and Gloss
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Solution Overview
Problem
Conventional UV-curable inkjet systems suffer from poor image quality due to the combination of neighboring droplets during high-speed recording, leading to surface irregularities and insufficient glossiness in printed images, as the gelling agents used cause the ink to become highly viscous and difficult to level.
Innovation Solution
An actinic radiation-curable inkjet ink comprising a photocurable compound, a photopolymerization initiator, a gelling agent, and a liquid compound with specific properties, including a (meth)acrylate compound with a C Log P value between 4.0 and 7.0, and a liquid compound with an SP value of 8.5 or more and a boiling point between 120° C and 200° C, which prevents droplet combination and enhances glossiness and smoothness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a gelling agent is added to UV-curable inkjet ink to prevent combining of neighboring droplets, then droplet combination is prevented, but the ink becomes highly viscous and difficult to level, producing surface irregularities and insufficient glossiness
Solution Approach 1:
The patent changes the chemical parameters of the ink by introducing a liquid compound with specific properties (SP value of 8.5 or more and boiling point of 120°C or higher and lower than 200°C). This parameter change allows the ink to maintain appropriate viscosity for leveling while preventing droplet combination, thereby resolving the contradiction between droplet separation and surface smoothness
Solution Approach 2:
The patent creates a composite ink formulation combining multiple components: photocurable compound, photopolymerization initiator, gelling agent, and the specially selected liquid compound. This composite material approach allows the ink to exhibit multiple desirable properties simultaneously - preventing droplet combination while maintaining levelability and producing high-gloss surfaces
2Manufacturing precision
If the density of printed image is adjusted by the amount of ink droplets, then image density is controlled, but film thickness varies significantly, causing level differences at boundaries between regions of different density
Solution Approach 1:
The patent modifies the physical parameters of the ink by adding a liquid compound with specific boiling point and SP value characteristics. This enables the ink to maintain consistent flow and leveling properties across different ink amounts, reducing film thickness variation and level differences at density boundaries while preserving image density control
3Productivity
If high-speed recording is performed using line recording head or high speed serial recording, then productivity is improved, but neighboring dots combine together, degrading image quality
Solution Approach 1:
The patent changes the viscosity and flow parameters of the ink through the addition of the liquid compound with specific properties. This allows the ink to resist droplet combination at high recording speeds while maintaining printability, enabling high-speed recording without sacrificing image quality
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 effectively prevents droplet combination, resulting in high-quality images with improved glossiness and reduced surface irregularities, while maintaining stable discharge and adhesion to the recording medium.
Implementation Method 1
curing the droplets landed on the recording medium by irradiating the droplets with actinic radiation
Implementation Method 2
the inkjet ink undergoes gelation quickly after the ink is landed on a recording medium
Data Source
AI summary
An active ray-curable inkjet ink which contains a photocurable compound, a photopolymerization initiator, a gelling agent and a non-polymerizable liquid compound that is in a liquid state at 25° C., with the liquid compound being contained in an amount of 15-50% by mass relative to the mass of the ink. Since droplets of this active ray-curable inkjet ink are prevented from combining with each other after landing, this active ray-curable inkjet ink is capable of providing high quality images. Meanwhile, the surface gloss of printed images is increased, and printed images having less coating film thickness difference (namely, less relief-like texture) can be formed.