Piezoelectric Element Surface Roughness for Inkjet Discharge Stability
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Solution Overview
Problem
Inkjet recording systems face discharge defects and unevenness due to uneven pressure distribution across nozzles, leading to bubble formation and ink charging issues, which affect continuous discharging properties and speed.
Innovation Solution
The system ensures that the average surface roughness of the piezoelectric element and ink viscosity fall within specific ranges, with relational expressions governing their interaction, and the average inclination of the piezoelectric element is adjusted to optimize ink charging and discharging, using a combination of surface treatments and ink composition to enhance wettability and reduce bubble formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of nozzles is increased to improve printing speed, then productivity increases, but pressure distribution becomes unequal causing bubble formation and discharge defects
Solution Approach 1:
The invention applies local quality by treating the inner wall surface of the ink flow channel with hydrophilic treatment (acid treatment or plasma treatment) to create a specific local property. This localized treatment improves wettability at critical areas where bubbles tend to form and attach, thereby maintaining reliable continuous discharging even when the number of nozzles is increased for higher printing speed.
2Manufacturing precision
If acid treatment or plasma treatment is applied to improve wettability, then ink charging improves, but piezoelectric elements may get corroded or deteriorated
Solution Approach 1:
The invention uses an intermediary approach by applying hydrophilic treatment (acid treatment or plasma treatment) to the inner wall surface of the ink flow channel, which acts as a mediator between the ink and the piezoelectric element. This treatment improves ink wettability and charging without requiring direct treatment of the piezoelectric element itself, thereby avoiding corrosion and deterioration of the piezoelectric materials.
3Strength
If burnt piezoelectric elements are used to increase toughness, then strength improves, but surface becomes bumpy making ink charging difficult
Solution Approach 1:
The invention resolves this contradiction by applying local quality treatment to the inner wall surface of the ink flow channel adjacent to the piezoelectric element. By treating this specific local area with hydrophilic coating or plasma treatment, the invention compensates for the poor wettability caused by the burnt surface, enabling proper ink charging while maintaining the strength benefits of the burnt piezoelectric element structure.
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 improves the initial charging and continuous discharging properties of inkjet recording systems, reducing image unevenness and maintaining high discharging speed by ensuring optimal surface roughness, viscosity, and ink-piezoelectric element interaction.
Implementation Method 1
a part of wall face of a pressure chamber in which a nozzle is provided is formed of a piezoelectric element, and the piezoelectric element is activated and deformed to make pressure wave act on ink in the pressure chamber
Implementation Method 2
a method of imparting hydrophilicity by acid treatment or plasma treatment, or of containing a filler imparted with hydrophilicity by acid treatment has been proposed to improve the wettability of a head constituting member
Implementation Method 3
surface roughness Ra of the piezoelectric element and viscosity of the ink fall within a predetermined range, and a value calculated from a relational expression between surface roughness of the piezoelectric element and physical property value of the ink is larger than or equal to a predetermined value
Data Source
AI summary
An inkjet recording system includes an inkjet recording head in which a part of wall face of a pressure chamber in which a nozzle is provided is formed of a piezoelectric element. Centerline average roughness Ra of the piezoelectric element is 0.05 to 2 μm, viscosity of the ink is 2.0 to 10.0 mPa·s, and the following expression (1) is satisfied;rγcosθ2η≥0.07(1)wherein r represents centerline average roughness (μm) of surface of piezoelectric element forming wall face of the pressure chamber, γ represents surface tension (mN/m) of ink, η represents viscosity of ink (mPa·s), and θ represents contact angle (degree) of ink with respect to piezoelectric element.