Ultra-Thin Touch Sensor Stack-Up Without Flex Circuits

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Solution Overview

Problem

Conventional touch screens have a thick stack-up structure due to the inclusion of flex circuits and separate substrates for touch sensor panels and polarizers, which increases device thickness, weight, and reduces optical image quality by increasing the display-to-cover glass distance.

Innovation Solution

The implementation of an ultra-thin touch screen stack-up design that eliminates flex circuits and integrates the touch sensor panel with the polarizer using a flexible substrate, allowing routing of touch electrodes and shield layers to reduce thickness and weight, and improves optical image quality by minimizing the display-to-cover glass distance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If flex circuits and separate substrates are used for touch sensor panels and polarizers, then the touch screen can be assembled with standard components, but the device thickness and weight increase

Engineering Contradiction:

Improveassembly with standard componentsVSAvoiddevice thickness

Core Design Contradiction:

Ease of manufactureVSLength of stationary object

Solution Approach 1:

The patent combines the touch sensor panel and polarizer onto a single substrate, eliminating the need for separate substrates and flex circuits. This integration directly reduces the device thickness by removing redundant layers and interfaces while maintaining the functionality of both components.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent extracts and eliminates the flex circuit from the stack-up by routing touch electrodes and shield layers directly on the substrate. This removal of the flex circuit component directly reduces both thickness and weight while the routing is reconfigured to achieve the same electrical connections.

Inventive Principle:

Principle #2Taking out (Extraction)

2Ease of manufacture

If flex circuits and separate substrates are used for touch sensor panels and polarizers, then the touch screen can be assembled with standard components, but the device weight increases

Engineering Contradiction:

Improveassembly with standard componentsVSAvoiddevice weight

Core Design Contradiction:

Ease of manufactureVSWeight of stationary object

Solution Approach 1:

The patent merges the touch sensor panel and polarizer onto one substrate, eliminating duplicate substrate materials and adhesive layers. This consolidation reduces the total material mass, directly decreasing device weight while maintaining structural integrity and component functionality.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent removes the flex circuit from the assembly by integrating its routing function directly into the substrate. This extraction eliminates the additional weight of the flex circuit while the routing is reconfigured to provide the same electrical connections more efficiently.

Inventive Principle:

Principle #2Taking out (Extraction)

3Ease of manufacture

If the display to cover glass distance is increased, then the assembly process is easier, but the optical image quality deteriorates

Engineering Contradiction:

Improveassembly processVSAvoidoptical image quality

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent integrates the touch sensor panel and polarizer onto the same substrate, reducing the overall stack-up thickness. This integration minimizes the display-to-cover glass distance, improving optical image quality by reducing light scattering and reflection interfaces while the precise routing maintains assembly feasibility.

Inventive Principle:

Principle #5Merging (Combining)

4Adaptability or versatility

If separate substrates are used for touch sensor panel and polarizer, then each component can be optimized independently, but the overall device complexity increases

Engineering Contradiction:

Improvecomponent optimizationVSAvoidstack-up structure

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent combines the touch sensor panel and polarizer onto a single substrate, simplifying the stack-up structure by reducing the number of layers and interfaces. This integration reduces device complexity while the routing is designed to maintain the functional optimization of both components through proper electrical connections and shielding.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS12197684B2Ultra-thin touch sensors

Publication Date: 2025.01.14 APPLE INC

AI summary

Touch screens with ultra-thin stack-ups can provide for a lower profile device, can improve the optical image on the display by reducing the display to cover glass distance, and can reduce the weight of the device. In some examples, the thickness of the touch screen stack-up can be reduced and/or the border region reduced, by removing the flex circuit connection from the stack-up. A flexible substrate can be used to enable routing of touch electrodes to touch circuitry. In some examples including a shield layer, the thickness of the touch screen stack-up can be reduced by routing the shield layer to a shield electrode on the touch sensor panel. The shield layer can then be routed to touch sensing circuitry via the flexible substrate. In some examples, the touch sensor panel or a portion of thereof can be integrated with the polarizer.