LED Print Heads for Uniform Jetting and Energy Efficiency
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Solution Overview
Problem
Existing print head technologies using resistive heating for inkjet printing face issues such as non-uniform jetting, high energy consumption, and compatibility limitations due to heat dissipation and material reactions with resistor surfaces, leading to inconsistent print quality and restricted material usage.
Innovation Solution
The use of Light Emitting Diodes (LEDs) emitting ultraviolet light to heat the print fluid, where colorants absorb energy and radiate heat, reducing energy loss and allowing for lower working temperatures, increased efficiency, and broader compatibility with print agents, while beam shaping elements focus energy away from the print head surfaces to prevent deposits and extend nozzle life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If resistive heating is used to heat print fluid, then printing function is achieved, but energy consumption increases and heat dissipation causes non-uniform jetting
Solution Approach 1:
The patent replaces the resistive heating system with an optical heating system using LEDs. The LED emits light that is absorbed by the print fluid, converting optical energy directly to thermal energy at the fluid location rather than through resistive heating of a substrate. This substitution eliminates the heat dissipation issues and energy loss associated with resistive heating, achieving both lower energy consumption and more uniform heating.
Solution Approach 2:
The patent introduces light as an intermediary between the power source and the print fluid. The LED converts electrical energy to optical energy, which then transfers energy to the print fluid through absorption. This intermediary approach allows precise control of where and how heat is generated in the fluid, avoiding the heat dissipation problems of direct resistive heating while maintaining efficient energy transfer.
2Speed
If high temperature heating is used to eject print agent, then droplet ejection is achieved, but material reactions with resistor surfaces occur and deposits form
Solution Approach 1:
The patent replaces contact-based resistive heating with contactless optical heating. The LED emits light that heats the print fluid without physical contact, eliminating the chemical reactions and deposit formation that occur when hot print fluid contacts resistor surfaces. This maintains the ability to achieve high temperatures for droplet ejection while avoiding the harmful material interactions.
Solution Approach 2:
The patent extracts the heating function from the substrate/resistor and relocates it to the print fluid itself through optical absorption. By using LEDs to illuminate the fluid and having the fluid absorb the energy directly, the harmful interaction between heated material and resistor surface is completely removed, while the temperature elevation needed for droplet ejection is preserved.
3Ease of manufacture
If resistive heating is used, then printing function is achieved, but compatibility with print agents is restricted
Solution Approach 1:
The patent changes the heating mechanism parameter from resistive (contact-based) to optical (contactless). This parameter change fundamentally alters the interaction between the heating system and print agents, removing chemical compatibility constraints. Different print agents can be used based on their optical absorption properties rather than their chemical reactivity with resistors, greatly expanding material versatility.
Solution Approach 2:
By substituting optical heating for resistive heating, the patent eliminates the chemical interface between the heating element and print agent. This substitution removes the compatibility restrictions that arise from material reactions, allowing a broader range of print agents to be used without concern for chemical interactions with heating surfaces.
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
This approach results in improved print quality, reduced energy consumption, increased print speed, and extended apparatus lifespan by minimizing heat-related issues and allowing for a wider range of print agents, despite initial complexity and cost, offset by increased efficiency and performance.
Implementation Method 1
A Light Emitting Diode (LED) 106 which, in use of the print head 100, emits light to heat printing fluid in the fluid channel 104
Implementation Method 2
causing localised vaporisation of the printing fluid and ejection of a fluid drop
Implementation Method 3
beam shaping elements focus energy away from the print head surfaces to prevent deposits
Data Source
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Figure 6
AI summary
In an example, a print head includes a nozzle, a fluid channel to provide printing fluid to the nozzle and a Light Emitting Diode (LED). The LED may emit light to heat printing fluid in the fluid channel causing localised vaporisation of the printing fluid and ejection of a fluid drop through the nozzle.