Cover Plate Refractive Index Design for Electrophoretic Display Light Leakage

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

In electrophoretic display devices, light leakage occurs due to light passing from the light guide plate into the cover plate and optical adhesive, reducing display quality.

Innovation Solution

A cover plate structure with a first light transmitting layer having a higher refractive index than the second light transmitting layer and optical adhesive layer, combined with a light shielding layer, enables total internal reflection and absorption of light in non-display regions, reducing side surface light leakage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If light guide plate and cover plate are adhered by optical adhesive, then light transmission is enabled, but light leakage occurs at the interface

Engineering Contradiction:

Improvelight transmissionVSAvoidlight leakage

Core Design Contradiction:

Illumination intensityVSObject-generated harmful factors

Solution Approach 1:

The patent changes the refractive index parameter of the cover plate material. The first light transmitting layer is configured with a refractive index greater than both the second light transmitting layer and the optical adhesive layer, creating conditions for total internal reflection at the interfaces, thereby preventing light leakage while maintaining light transmission functionality

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent converts the harmful light leakage into beneficial total internal reflection. By designing the refractive index relationship appropriately, the light that would otherwise leak out is reflected back into the display structure, where it can be redirected to non-display regions and absorbed, turning a defect into a functional feature

Inventive Principle:

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

2Loss of energy

If first light transmitting layer is thinned, then total internal reflection efficiency increases, but structural strength may decrease

Engineering Contradiction:

Improvelight leakage reductionVSAvoidstructural strength

Core Design Contradiction:

Loss of energyVSStrength

Solution Approach 1:

The patent uses a composite structure with multiple light transmitting layers having different refractive indices. The first light transmitting layer with higher refractive index is positioned to create total internal reflection interfaces, while the overall structure maintains mechanical strength through the layered composite design

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent applies different refractive index properties to different layers locally. The first light transmitting layer has a specifically engineered refractive index greater than the other layers, creating localized optical functionality for total internal reflection at specific interfaces without requiring the entire structure to be optimized for the same function

Inventive Principle:

Principle #3Local quality

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 reduces light leakage by 25% to 35% from the side surfaces of the display apparatus, enhancing display quality by effectively directing and absorbing stray light.

Implementation Method 1

By a configuration of a first light transmitting layer having a refractive index greater than a refractive index of a second light transmitting layer and greater than a refractive index of the optical adhesive layer, total internal reflection can occur at an interface between the first light transmitting layer and the second light transmitting layer and at an interface between the first light transmitting layer and an optical adhesive layer

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Implementation Method 2

by thinning the first light transmitting layer, the light undergone total internal reflection can pass to the non-display region on two sides of the display apparatus and gives an increased possibility of being absorbed by the light shielding layer

Methodology Applied

Scientific EffectLight absorption: Absorption (EM radiation)

Data Source

PatentUS11042070B2Cover plate structure and display apparatus

Publication Date: 2021.06.22 E INK HLDG INC

AI summary

A cover plate structure includes a first light transmitting layer, a second light transmitting layer, and a light shielding layer. The first light transmitting layer includes a top surface and a bottom surface opposite the top surface. The second light transmitting layer is on the top surface of the first light transmitting layer. A refractive index of the first light transmitting layer is greater than a refractive index of the second light transmitting layer. The light shielding layer is on the bottom surface of the first light transmitting layer.