Uncoated Inkjet Substrate Sizing via Cationic Polymers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current uncoated inkjet substrates lack optimal printing properties such as water fastness, optical density, and color gamut, especially when used with high-speed inkjet printing devices, due to limitations in their sizing layers.
Innovation Solution
An uncoated inkjet substrate with an unpigmented sizing layer composed of a combination of cationic inorganic polyaluminium hydroxychloride and organic cationic polydimethylammonium compounds, applied at a pH of less than 6, forming a solution and dispersion respectively, to create a final dried layer with improved printing properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a strong pigmented layer is used as ink receiving layer, then water fastness and optical density are improved, but the substrate becomes coated rather than uncoated, losing the natural feel and increasing complexity
Solution Approach 1:
The patent changes the chemical parameters of the sizing layer by using a specific pH range (4-6) and combining cationic starch with cationic polymeric compounds. This creates an uncoated substrate that achieves water fastness equivalent to coated substrates through chemical modification rather than adding coating layers.
Solution Approach 2:
The patent creates a composite sizing layer combining cationic starch (0.5-5% dry weight) with cationic polymeric compounds. This composite structure provides both the water fastness of pigmented layers and maintains the uncoated character by integrating functionality into the sizing layer itself.
2Reliability
If a thick pigmented ink receiving layer is applied, then optical density and color gamut are improved, but drop spreading becomes excessive and printing precision deteriorates
Solution Approach 1:
The patent optimizes the pH parameter of the sizing layer to range between 4 and 6, which controls the charge density and interaction with ink droplets. This parameter optimization allows achieving high optical density while maintaining precise drop spreading control, preventing both excessive spreading and insufficient absorption.
3Ease of manufacture
If conventional sizing layers are used, then manufacturing simplicity is maintained, but printing properties such as water fastness and color gamut are insufficient for high-speed inkjet printing
Solution Approach 1:
The patent modifies conventional sizing by adjusting the pH to 4-6 and incorporating cationic starch with cationic polymeric compounds. This parameter change maintains the simplicity of the sizing process (applied at the paper machine) while dramatically improving printing properties for high-speed inkjet printing.
Solution Approach 2:
The patent creates a composite sizing layer combining cationic starch (0.5-5% dry weight) with cationic polymeric compounds. This composite approach maintains manufacturing simplicity by applying the mixture in a single sizing operation at the paper machine, while achieving superior water fastness, optical density, and color gamut.
4Device complexity
If the sizing layer is made thinner to maintain uncoated character, then natural feel is preserved, but ink receiving capacity and optical density decrease
Solution Approach 1:
The patent changes the chemical composition and pH of the sizing layer to maximize ink interaction efficiency. By using cationic starch with cationic polymeric compounds at pH 4-6, the thin sizing layer achieves high ink receiving capacity and optical density without needing to be thick, preserving the uncoated character.
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 substrate exhibits high water fastness, exceptional optical densities, and excellent color gamut, along with sufficient drop spreading, making it suitable for a wide range of printer devices.
Implementation Method 1
sizing layer essentially consists of a combination of a cationic inorganic polyaluminium hydroxychloride compound with at least one organic cationic polydimethylammonium compound
Implementation Method 2
sizing formulation is applied as an aqueous formulation at a pH of less than 6 in which the cationic inorganic polyaluminium hydroxychloride is in solution and the cationic polydimethylammonium compound is in dispersion
Data Source
Figure 1
AI summary
An inkjet printable substrate (1) with an essentially unpigmented sizing layer (3) on at least one surface of a raw cellulosic substrate (2) is proposed, wherein the sizing layer (3) essentially consists of a combination of a polyaluminium hydroxychloride compound with at least one organic cationic polydimethylammonium compound, applied as an aqueous formulation at a pH of less than 6 in which the polyaluminium hydroxychloride is in solution and the cationic polydimethylammonium compound is in dispersion.