Touch LCD Anti-Static Layer for Capacitive Sensing
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Solution Overview
Problem
Touch sensing capabilities are hindered in IPS and FFS mode LCD devices due to the anti-static layer made of transparent conductive materials like ITO and IZO, which discharge static electricity, preventing the detection of capacitance changes generated by user touch.
Innovation Solution
Incorporating an anti-static layer on the outer side of the upper substrate comprising an organic material and carbon nano-tubes, offering a sheet resistance of 106 to 109 ohms per square, allowing for effective static electricity dissipation without obstructing touch sensing by functioning as a dielectric layer between the finger and the common electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an anti-static layer made of transparent conductive materials (ITO, IZO) is used, then static electricity is dissipated effectively, but touch sensing capability is hindered because the layer discharges static electricity and prevents detection of capacitance changes
Solution Approach 1:
The patent uses a composite anti-static layer comprising carbon nanotubes dispersed in a transparent resin material. This composite structure combines the high electrical conductivity of carbon nanotubes for static dissipation with the electrical insulation properties of the resin, allowing simultaneous achievement of static protection and touch sensing capability. The carbon nanotubes form conductive pathways for static electricity while the resin matrix prevents these pathways from interfering with touch capacitance detection.
Solution Approach 2:
The patent optimizes the concentration of carbon nanotubes in the anti-static layer to achieve the desired balance between static dissipation and touch sensing. By controlling the amount of carbon nanotubes and their distribution, the layer provides sufficient conductivity for static protection while maintaining enough electrical insulation to allow capacitance change detection for touch sensing.
2Device complexity
If a conventional transparent conductive anti-static layer is used, then the device structure is simple, but the touch sensing signal is obstructed by the conductive nature of the layer
Solution Approach 1:
The composite anti-static layer maintains structural simplicity as a single layer while achieving dual functionality. The combination of carbon nanotubes and transparent resin in one layer provides both static dissipation and touch sensing transparency, eliminating the need for additional layers or complex structures while preserving touch detection accuracy.
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
Enables the detection of touch input by forming a capacitor between the finger and the common electrode, allowing for accurate position sensing while preventing damage from static electricity, as the anti-static layer serves as a conductive path for static electricity and an insulating layer for touch-related currents.
Implementation Method 1
an anti-static layer on an outer side of the second substrate and including an organic material and a carbon nano-tube
Implementation Method 2
Enables the detection of touch input by forming a capacitor between the finger and the common electrode
Implementation Method 3
the anti-static layer serves as a conductive path for static electricity and an insulating layer for touch-related currents
Data Source
AI summary
A touch sensing type liquid crystal display device includes an array substrate includes a first substrate, a common electrode, a pixel electrode, and a touch sensing unit; a color filter substrate including a second substrate and facing the array substrate; an anti-static layer on an outer side of the second substrate and including an organic material and a carbon nano-tube; and a liquid crystal layer between the first substrate and an inner side of the second substrate.