Colorless Inkjet Coating for Durability and Gloss Control
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Solution Overview
Problem
Pigment-based inkjet inks face challenges with durability and gloss control, particularly in continuous inkjet systems, where wax particles can cause instability and aggregation, leading to issues like plugged filters and crooked jets, while existing solutions may compromise on image quality or durability.
Innovation Solution
Aqueous colorless inkjet ink compositions comprising anionic polyether polyurethane and anionic acrylic or styrene-acrylic polymers, without UV curable components or wax particles, are used to provide a visible colorant-free, non-UV curable coating that can be digitally applied over colored images, enhancing durability and adjustability of glossiness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wax particles are added to pigment-based inkjet inks to improve durability and gloss control, then image durability and gloss control are improved, but system stability deteriorates due to particle aggregation and clogging
Solution Approach 1:
The invention extracts and removes wax particles from the inkjet ink composition entirely, replacing them with a polymer-based system consisting of polyurethane and acrylic/ styrene-acrylic polymers. This elimination of solid particles resolves the clogging and aggregation problems while maintaining the desired durability and gloss control properties through the polymer matrix.
Solution Approach 2:
The invention changes the fundamental compositional parameters of the ink by transitioning from a wax-particle-based system to a polymer-based system. Specifically, it uses polyurethane polymers with controlled molecular weights (1,000-100,000 Daltons) and acrylic/styrene-acrylic polymers with carboxy groups, creating a particle-free composition that maintains durability without the instability associated with wax particles.
2Illumination intensity
If pigment-based inks are used to improve color density and light-fastness, then optical quality is improved, but water fastness and smear resistance deteriorate
Solution Approach 1:
The invention creates a composite ink system that combines pigment particles for optical properties with a polymer matrix (polyurethane and acrylic/styrene-acrylic polymers) for protective properties. The polymer coating that forms upon drying provides water fastness and smear resistance while the pigment maintains color density and light-fastness, achieving both sets of properties through material composition.
3Reliability
If UV curable components are included in the ink composition to enhance durability, then image durability is improved, but complexity and potential harmful effects increase
Solution Approach 1:
The invention extracts and removes UV curable components from the ink composition entirely, creating a non-UV curable formulation. The durability is achieved through the polymer matrix (polyurethane and acrylic/styrene-acrylic polymers) that forms a protective coating upon drying, eliminating the need for UV curing chemistry and associated complexity while maintaining durability performance.
Data Source
AI summary
Colorless coatings can be ink jetted onto part or all of colored images as spaced colorless drops to provide a colorless image over at least 50% of colored areas of the colored image and on a predetermined areal percentage of non-colored areas of the colored image. The aqueous colorless inkjet ink composition has a viscosity of less than 0.005 N-sec at 25° C., and comprises an anionic polyether polyurethane and an anionic acrylic or styrene-acrylic polymer, each having an acid number of at least 50, and such polymeric materials are present in unique amounts. Use of the aqueous colorless inkjet ink composition can be adjusted to provide increased gloss on the colored image in either or both of the colored area or non-colored areas.