Fingerprint Sensing Electrode Layer with Composite Protection

Solution Overview

Problem

Conventional capacitive fingerprint identification in display devices faces a tradeoff between protection layer durability and accurate sensing, with glass protection layers being prone to breakage under inappropriate pressure and increasing thickness leading to inaccurate sensing due to reduced signal differentiation. Additionally, integrating capacitive fingerprint identification with flat display devices is challenging due to different manufacturing processes.

Innovation Solution

A display device with a thin-film-transistor-and-sensing-electrode layer that forms multiple macro sensing electrode blocks at different positions, allowing for fingerprint image detection and touch sensing directly on the viewing area without occupying additional space, using sensing electrodes made of materials like indium tin oxide, zinc tin oxide, conductive polymers, nano silver, or graphene.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the thickness of the protection layer is decreased to improve fingerprint sensing accuracy, then the sensing precision is improved, but the protection layer becomes prone to breakage under inappropriate pressure

Engineering Contradiction:

Improvefingerprint sensing accuracyVSAvoidprotection layer durability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent applies composite materials by combining multiple protective layers with different properties. Specifically, it uses a first protection layer (50-100 μm thick) made of a first material and a second protection layer (3-10 μm thick) made of a second material, where the second layer has higher hardness than the first. This composite structure allows the softer first layer to absorb stress and prevent breakage while the harder second layer maintains fingerprint sensing accuracy by providing appropriate rigidity and surface characteristics.

Inventive Principle:

Principle #40Composite materials

2Reliability

If the thickness of the protection layer is increased to prevent breakage, then the protection layer durability is improved, but the fingerprint sensing accuracy deteriorates due to reduced signal differentiation

Engineering Contradiction:

Improveprotection layer durabilityVSAvoidfingerprint sensing accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent applies composite materials by combining multiple protective layers with different properties. Specifically, it uses a first protection layer (50-100 μm thick) made of a first material and a second protection layer (3-10 μm thick) made of a second material, where the second layer has higher hardness than the first. This composite structure allows the softer first layer to absorb stress and prevent breakage while the harder second layer maintains fingerprint sensing accuracy by providing appropriate rigidity and surface characteristics.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent applies segmentation by dividing the protection layer into multiple distinct layers with different thicknesses and material properties. The first protection layer (50-100 μm) and second protection layer (3-10 μm) are segmented to perform different functions: the thicker first layer provides mechanical strength and breakage resistance, while the thinner second layer ensures accurate capacitive sensing by maintaining appropriate distance from the sensing elements.

Inventive Principle:

Principle #1Segmentation

3Reliability

If a sapphire material is used for the protection layer to prevent breakage, then the protection layer durability is improved, but the manufacturing cost increases

Engineering Contradiction:

Improveprotection layer durabilityVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent applies this principle by replacing expensive sapphire material with more cost-effective materials that can achieve the same protective function. Instead of using a single thick sapphire layer, the patent uses a composite structure with a first protection layer (50-100 μm) and a second protection layer (3-10 μm) made of materials that are cheaper than sapphire but provide equivalent durability through their combined properties.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent applies composite materials by combining multiple protective layers with different properties. Specifically, it uses a first protection layer (50-100 μm thick) made of a first material and a second protection layer (3-10 μm thick) made of a second material, where the second layer has higher hardness than the first. This composite structure allows the softer first layer to absorb stress and prevent breakage while the harder second layer maintains fingerprint sensing accuracy by providing appropriate rigidity and surface characteristics.

Inventive Principle:

Principle #40Composite materials

4Adaptability or versatility

If conventional capacitive fingerprint identification is integrated into flat display devices, then the device functionality is improved, but the integration is challenging due to different manufacturing processes

Engineering Contradiction:

Improvedevice functionalityVSAvoidintegration difficulty

Core Design Contradiction:

Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

The patent applies universality by designing a protection layer structure that serves multiple functions: it protects the fingerprint sensing elements, enables accurate capacitive sensing, and is compatible with the display device manufacturing process. The first protection layer (50-100 μm) and second protection layer (3-10 μm) together provide mechanical protection, electrical insulation, and appropriate capacitive coupling, allowing the same structure to fulfill multiple requirements of both fingerprint sensing and display manufacturing.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 accurate fingerprint identification of multiple fingers simultaneously while preventing protection layer breakage and integrating fingerprint detection seamlessly with touch sensing, suitable for narrow-border handheld devices.

Implementation Method 1

the capacitive finger identification sensor has a plurality of sensing elements 11, and the fingerprint 13 presses on a non-conductive protection layer 12

Methodology Applied

Scientific EffectCapacitance sensing: Capacitance

Implementation Method 2

the thin-film-transistor-and-sensing-electrode layer having a plurality of sensing electrodes for performing fingerprint identification sensing and touch sensing

Methodology Applied

Scientific EffectCapacitance sensing: Capacitance

Data Source

PatentUS10048795B2Display device with fingerprint identification and touch detection

Publication Date: 2018.08.14 SUPERC TOUCH CORP

AI summary

A display device with fingerprint identification and touch detection includes a first substrate, a second substrate parallel to the first substrate, a display material layer configured between the first substrate and the second substrate, and a thin-film-transistor-and-sensing-electrode layer. The thin-film-transistor-and-sensing-electrode layer is disposed at one surface of the first substrate facing the display material layer. The thin-film-transistor-and-sensing-electrode layer has a plurality of sensing electrodes for performing fingerprint identification sensing and touch sensing at the same time.