Liquid Ejection Substrate Scallop Geometry for Meniscus Stability
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Solution Overview
Problem
The existing liquid ejection technologies face instability in droplet ejection due to large initial scallops in the ejection holes, which lead to meniscus instability and potential oblique setup, resulting in unstable ejection.
Innovation Solution
A substrate for a liquid ejection head with ejection holes featuring a specific configuration of scallops, where the first scallop is narrower and shallower than the second scallop, and the ratio of width to depth in the first scallop is greater than or equal to 4, to stabilize the meniscus and ensure stable ejection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If etching is performed at a high rate to improve productivity, then the initial scallop becomes larger, but the meniscus becomes less likely to be formed and ejection stability deteriorates
Solution Approach 1:
The invention applies different scallop depth characteristics to different positions within the ejection hole. The first scallop (at the opening end) has a depth-to-width ratio of 0.05 or less, while the second scallop (deeper in the hole) has a depth-to-width ratio of 0.15 or less. This local differentiation allows the opening region to maintain meniscus stability while still permitting high-rate etching overall, thus resolving the contradiction between productivity and ejection stability.
2Manufacturing precision
If the opening dimension is reduced to about 100 μm or less, then ions or radicals become less likely to enter the hole, but the scallops gradually become smaller and meniscus formation becomes more difficult
Solution Approach 1:
The invention changes the geometric parameters of the scallops, specifically controlling the depth-to-width ratio to be 0.05 or less at the opening end. This parameter optimization ensures that even when opening dimensions are reduced to 100 μm or less, the meniscus can still be properly formed and maintained, resolving the contradiction between manufacturing precision and meniscus formation stability.
3Ease of manufacture
If the angle of the depressed portion of the scallop is large, then the initial scallop becomes larger, but the meniscus becomes less likely to be formed and may set up obliquely
Solution Approach 1:
The invention creates a localized shallow scallop structure at the opening end of the ejection hole, where the depth-to-width ratio is 0.05 or less. This local quality control ensures proper meniscus formation and vertical orientation, while allowing larger scallops deeper in the hole that are easier to manufacture. This resolves the contradiction between ease of manufacture and meniscus formation precision.
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 proposed substrate configuration enables stable ejection of liquids by maintaining meniscus stability at the ejection hole surface, even under high etching rates, thus improving the reliability of liquid ejection processes.
Implementation Method 1
a piezoelectric element provided on the actuator substrate
Implementation Method 2
the Bosch Process in which a silicon substrate is penetrated... etching and coating are alternately repeated
Data Source
AI summary
A substrate for use in a liquid ejection head has an ejection hole for ejecting a liquid from the inside to the outside of the substrate. A plurality of scallops periodically changing the diameter of an inner circumferential surface of the ejection hole in the penetration direction are formed on the inner circumferential surface. The substrate for a liquid ejection head is characterized in that a width in the penetration direction of a first scallop present on the outermost side among the plurality of scallops is narrower than a width in the penetration direction of a second scallop adjacent to the first scallop on the inward side, and a depth in a radial direction of the ejection hole of the first scallop is shallower than a depth in the radial direction of the ejection hole of the second scallop.