Zigzag Metal Wiring for Touch Screen Parasitic Capacitance Reduction

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Solution Overview

Problem

Conventional Projected Capacitive Touchscreens face challenges in increasing size due to high resistance of transparent conductive layers, leading to reduced display quality, visibility issues, and parasitic capacitances, which affect sensitivity and response speed, and cause display unevenness and moires.

Innovation Solution

The design incorporates a touch screen with detection column and row wirings formed by metal conductive wires arranged in zigzag patterns with sloped and parallel portions, interconnected to reduce parasitic capacitances and increase wiring density, while minimizing visibility and maintaining high sensitivity and response speed.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If transparent conductive layers are used as detection wirings, then display quality is maintained, but resistance increases and touch panel size cannot be increased

Engineering Contradiction:

Improvedisplay qualityVSAvoidresistance

Core Design Contradiction:

Illumination intensityVSReliability

Solution Approach 1:

The patent uses a composite structure combining transparent conductive layer and metal wiring layer. The transparent conductive layer (ITO) provides optical transparency for display quality, while the metal wiring layer (Aluminum) provides low resistance for reliable signal transmission. This composite approach resolves the contradiction between maintaining display quality and reducing resistance.

Inventive Principle:

Principle #40Composite materials

2Reliability

If metal layers are used as detection wirings, then resistance is reduced, but reflected light increases and detection wirings become visible

Engineering Contradiction:

ImproveresistanceVSAvoiddisplay quality

Core Design Contradiction:

ReliabilityVSIllumination intensity

Solution Approach 1:

The patent combines transparent conductive layer with metal wiring layer in a composite structure. The metal layer provides low resistance while the transparent conductive layer above it reduces light reflection and makes the wirings invisible. This composite material approach resolves the contradiction between reducing resistance and maintaining display quality.

Inventive Principle:

Principle #40Composite materials

3Reliability

If thin metal conductive wires with increased wiring density are used, then resistance is reduced and touch panel size can be increased, but parasitic capacitances increase and wiring delays occur

Engineering Contradiction:

ImproveresistanceVSAvoidparasitic capacitances

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent segments the metal wiring into multiple independent linear portions connected by zigzag-shaped connection portions. This segmentation reduces the continuous metal area, thereby reducing parasitic capacitances between adjacent wirings while maintaining low resistance through the metal material. The zigzag connection portions electrically connect the linear portions while minimizing overlapping area.

Inventive Principle:

Principle #1Segmentation

4Illumination intensity

If conductor elements are made from transparent materials, then viewability is improved, but response speed decreases due to high electric resistance

Engineering Contradiction:

ImproveviewabilityVSAvoidresponse speed

Core Design Contradiction:

Illumination intensityVSSpeed

Solution Approach 1:

The patent creates a composite conductor system where the transparent conductive layer (ITO) provides optical transparency for viewability, while the metal wiring layer (Aluminum) provides high electrical conductivity for fast response speed. The two materials work together to resolve the contradiction between viewability and response speed.

Inventive Principle:

Principle #40Composite materials

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 a larger touch panel with improved capacitance detection sensitivity, reduced display unevenness, and minimized moires, enabling a higher response speed and better viewability without degrading display quality.

Implementation Method 1

detection column and row wirings formed by metal conductive wires arranged in zigzag patterns

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Implementation Method 2

interconnected to reduce parasitic capacitances and increase wiring density

Methodology Applied

Scientific EffectParasitic capacitance reduction: Parasitic Capacitance

Data Source

PatentUS8390598B2Touch screen, touch panel and display device

Publication Date: 2013.03.05 MITSUBISHI ELECTRIC CORP

AI summary

A detection column wiring includes a set of a first metal wiring having a zigzag pattern and a second metal wiring having a structure axisymmetric with the first metal wiring about a column direction. The first metal wiring includes first sloped portions obliquely sloped by an inclination angle of 45° with respect to the column direction, and first parallel portions parallel with the column direction and continuous with the first sloped portions; the first sloped portions and the first parallel portions being repeatedly placed in a zigzag shape along the column direction. Each detection row wiring has the same structure. A sloped portion of the first sloped portions of the first metal wiring is always orthogonally and spatially intersected, at its middle point, with a sloped portion of the second sloped portions of the third metal wiring at its middle point. Other portions have the same orthogonal relationship.