Electro-Optic Element With Capacitive Touch Decoupling
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Solution Overview
Problem
Integrating capacitive touchscreen functionality into electro-optic elements is challenging due to the mismatch in electrical current types (DC for electro-optic devices and AC for touchscreens) and increased capacitive load, which reduces sensitivity and increases response time.
Innovation Solution
An electro-optic element with integrated capacitive touchscreen functionality is designed using a first and second electro-optic conductive layer, a capacitive touchscreen conductive layer, and circuitry that drives these layers with in-phase AC voltages and a DC voltage offset, decoupling the touchscreen from ground to reduce capacitive loading and improve Signal-to-Noise Ratio (SNR).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conductive layer of the touchscreen element is placed over a conductive layer of the electro-optic element with only a thin insulating layer separating them, then touchscreen functionality is integrated, but the sensitivity of the touchscreen functionality is significantly reduced
Solution Approach 1:
A thick insulating layer is introduced as an intermediary between the touchscreen conductive layer and the electro-optic conductive layer. This thick insulating layer acts as a mediator that blocks the electrical field from being directed to the DC ground, thereby maintaining touchscreen sensitivity while allowing the two functional layers to remain in close proximity for integration.
2Strength
If the substrate covering the conductive layer of the touchscreen element is significantly thicker than the insulating layer, then structural support is provided, but the DC ground of the electro-optic portion directs the electrical field emitted by the touchscreen conductive layer, reducing sensitivity
Solution Approach 1:
The thick insulating layer serves as an effective intermediary that prevents the electrical field from penetrating through to the DC ground, even when the substrate is thick. This intermediary layer ensures that the substrate can be thick for structural support while the touchscreen sensitivity is maintained by blocking the harmful electrical field direction.
3Adaptability or versatility
If the electro-optic element is integrated with touchscreen functionality, then a unified device is created, but the capacitive load upon the touchscreen device increases, increasing the intrinsic sensor time constant and response time
Solution Approach 1:
The thick insulating layer acts as a capacitive barrier that reduces the total capacitive load on the touchscreen sensor. By increasing the insulation thickness, the parasitic capacitance between the touchscreen conductive layer and the electro-optic conductive layer is reduced, thereby decreasing the intrinsic sensor time constant and improving touchscreen response time while maintaining integration.
4Ease of operation
If AC voltage is used to drive the touchscreen conductive layer, then touchscreen operation is enabled, but the electro-optic device requires DC voltage for stable reference potential, creating a voltage type mismatch
Solution Approach 1:
The voltage supply system is segmented into separate AC and DC voltage sources. The touchscreen conductive layer is driven by AC voltage for touchscreen operation, while the electro-optic conductive layers are driven by DC voltage to maintain stable reference potential. This segmentation allows each subsystem to operate with its optimal voltage type without interfering with the other.
Solution Approach 2:
The electro-optic element structure is designed to support multiple voltage types simultaneously. The device can handle both AC voltage for touchscreen functionality and DC voltage for electro-optic operation, making it a multi-functional system that accommodates different electrical requirements within a single integrated 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 configuration allows for seamless integration of touchscreen functionality into electro-optic elements, enhancing sensitivity and reducing response time while maintaining electrochromic performance.
Implementation Method 1
A user's touch can thus be more easily determined as a function of the impedance change on the capacitive touchscreen conductive layer
Implementation Method 2
an electrochromic medium
Data Source
AI summary
An electro-optic element including: (i) an electrochromic medium; (a) a first electro-optic conductive layer that is substantially transparent disposed to one side of the electrochromic medium; (b) a second electro-optic conductive layer disposed to another side of the electrochromic medium; (c) a capacitive touchscreen conductive layer disposed on an opposite side of the first electro-optic conductive layer as the electrochromic medium, the capacitive touchscreen conductive layer comprising a pattern and being substantially transparent; (d) a capacitive touchscreen insulating layer disposed between the capacitive touchscreen conductive layer and the first electro-optic conductive layer; and (e) electrical circuitry configured (i) to drive the capacitive touchscreen conductive layer and at least one of the first electro-optic conductive layer and the second electro-optic conductive layer together with substantially in-phase AC voltage and (ii) to provide an input DC voltage difference between the first electro-optic conductive layer and second electro-optic conductive layer is substantially constant.