Touch Display Module Optics for True Black Light Leakage Control

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Solution Overview

Problem

Display panels fail to meet HDR 500 True Black™ specifications due to dark-state light leakage caused by interaction with touch-sensing layers, leading to increased production costs, power consumption, and stability issues.

Innovation Solution

A touch display module design with a plastic substrate having controlled birefringence and thickness in the touch-sensing layer, combined with optically clear adhesive and primer coating layers, to manage light propagation and reduce dark-state light leakage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the touch-sensing layer is laminated to the display panel, then the touch function is achieved, but dark-state light leakage occurs causing black level luminance to exceed HDR 500 True Black™ specifications

Engineering Contradiction:

Improvetouch functionVSAvoidblack level luminance

Core Design Contradiction:

Adaptability or versatilityVSIllumination intensity

Solution Approach 1:

An optically clear adhesive layer with refractive index of 1.40-1.49 is introduced between the touch-sensing layer and display panel. This intermediary layer manages light propagation by reducing total internal reflection at interfaces, thereby suppressing dark-state light leakage while maintaining touch functionality and achieving HDR 500 True Black™ black level luminance requirements

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The refractive index of the adhesive layer is specifically controlled to be lower (1.40-1.49) than conventional adhesives. This parameter change optimizes light propagation characteristics, reducing unwanted reflections and light leakage in dark states while maintaining optical clarity and touch sensitivity

Inventive Principle:

Principle #35Parameter changes

2Illumination intensity

If light-absorbing materials are deposited to reduce light leakage, then black level luminance is improved, but production complexity increases and display colors are affected

Engineering Contradiction:

Improveblack level luminanceVSAvoidproduction process complexity

Core Design Contradiction:

Illumination intensityVSDevice complexity

Solution Approach 1:

The solution extracts and removes the need for light-absorbing material deposition by using an optically clear adhesive layer instead. This eliminates the harmful light-absorbing materials and their associated production complexity while achieving the desired black level luminance through refractive index optimization

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces complex, expensive light-absorbing material deposition processes with a simpler, more cost-effective optically clear adhesive layer that achieves the same or better performance without affecting display colors or requiring additional production steps

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Illumination intensity

If voltage is adjusted to meet black level luminance requirements, then HDR specification is met, but power consumption increases and display stability deteriorates

Engineering Contradiction:

Improveblack level luminanceVSAvoiddisplay stability

Core Design Contradiction:

Illumination intensityVSReliability

Solution Approach 1:

The patent converts the harmful effect of total internal reflection (which causes light leakage) into a beneficial optical management system. By using an optically clear adhesive layer with optimized refractive index, light propagation is controlled to suppress dark-state leakage without requiring voltage adjustments, thereby maintaining both power efficiency and display stability while meeting HDR specifications

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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

The design achieves low black level luminance, meeting HDR 500 True Black™ standards while reducing production costs and maintaining display stability.

Implementation Method 1

The plastic substrate has a first refractive index and a second refractive index in different directions, and a difference (birefringence, Δn) between the first refractive index and the second refractive index is controlled to be smaller than or equal to 0.0001

Methodology Applied

Scientific EffectBirefringence: Birefringence

Implementation Method 2

A refractive index of the optically clear adhesive layer is 1.40 to 1.49, and is smaller than an average value of the first refractive index and the second refractive index

Methodology Applied

Scientific EffectRefraction: Refraction

Data Source

PatentUS20260082792A1Touch display module and display module

Publication Date: 2026.03.19 TPK ADVANCED SOLUTIONS

AI summary

A touch display module comprises a touch-sensing layer and an organic light-emitting diode display. The touch-sensing layer comprises a plastic substrate, a first metal mesh electrode layer, and a second metal mesh electrode layer. The thickness of the plastic substrate is 10 μm to 400 μm. The plastic substrate has a first refractive index and a second refractive index in different directions, and a difference (birefringence) between the first refractive index and the second refractive index is 0 to 0.0001. The first metal mesh electrode layer is disposed on the first surface. The second metal mesh electrode layer is disposed on a second surface, wherein the second surface is facing away from the first surface. The organic light-emitting diode display is disposed on one side of the touch-sensing layer. The maximum black level luminance of the touch display module is 0.0001 cd/m2 to 0.0005 cd/m2.