Variable Thickness ITO for Touch Sensor Panels
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Solution Overview
Problem
Large touch screens with mutual capacitance touch sensor panels face slow response times due to high RC time constants, which can be mitigated by increasing ITO thickness, but this introduces visual artifacts like color shift and reduced light transmission.
Innovation Solution
Implementing variable thickness ITO in non-regular, semi-random, or sparse arrangements on the touch sensor panel, along with conductive interconnects and dummy sections to reduce parasitic capacitance and maintain visual uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If uniformly thicker ITO coating is used to reduce RC time constant, then response speed is improved, but visual artifacts such as color shift and reduced light transmission are introduced
Solution Approach 1:
The patent applies different ITO coating thicknesses to different regions of the touch sensor panel. Thicker ITO coatings (e.g., 50-100 nm) are applied to drive and sense lines where electrical conductivity is critical for reducing RC time constant, while thinner ITO coatings (e.g., 10-30 nm) are applied to pixel regions where optical clarity is paramount. This spatial variation in coating thickness allows simultaneous optimization of electrical performance and visual quality.
Solution Approach 2:
The ITO coating is segmented into functionally distinct regions: conductive line regions with thicker coating for low resistance, and pixel regions with thinner coating for high transparency. The coating thickness is segmented to range from 10 nm in pixel areas to 100 nm in line areas, creating electrically optimized pathways without compromising overall visual appearance.
2Illumination intensity
If thinner ITO layer is used to maintain visual quality, then light transmission is improved, but RC time constant increases reducing scan rate
Solution Approach 1:
The patent implements local quality optimization by applying thin ITO coating (10-30 nm) specifically to pixel regions to maximize light transmission and minimize color shift, while applying thick ITO coating (50-100 nm) to drive and sense lines to minimize electrical resistance. This creates a dual-optimized structure where optical and electrical requirements are satisfied in their respective locations.
Solution Approach 2:
The patent resolves the contradiction by transitioning from a uniform one-dimensional thickness parameter to a two-dimensional thickness distribution map across the touch panel. The thickness varies continuously or discretely across the surface, allowing the system to optimize both light transmission (in pixel zones) and electrical conductivity (in line zones) simultaneously.
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 reduces the RC time constant without introducing visual artifacts, enhancing touch screen responsiveness and maintaining optical clarity.
Implementation Method 1
a substantially transparent conductive material, with a second resistivity that is lower than the first resistivity, can be deposited over at least part of at least one of the plurality of substantially transparent conductive sections
Implementation Method 2
the thickness of the ITO layer must be less than the thickness threshold where negative visual effects such as color shift become apparent
Implementation Method 3
At least one dummy section can be disposed in an area of the touch sensor panel around the conductive sections of at least one of the plurality of drive lines and the plurality of sense lines, in order to reduce parasitic capacitance and provide uniformity
Data Source
AI summary
A touch sensor panel including a plurality of drive lines crossing a plurality of sense lines, forming an array, is disclosed. The plurality of drive lines and the plurality of sense lines are formed by interconnecting a plurality of substantially transparent conductive sections having a first resistivity. A substantially transparent conductive material, with a second resistivity that is lower than the first resistivity, is deposited over at least part of at least one of the plurality of substantially transparent conductive sections of at least one of the plurality of drive lines and the plurality of sense lines. A second layer of the substantially transparent conductive material, with the second resistivity, can be deposited thereafter. At least one dummy section is disposed in an area of the touch sensor panel around the conductive sections of at least one of the plurality of drive lines and the plurality of sense lines.