Reflective Display Using Phase Change Material for Color and Luminance

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Solution Overview

Problem

Reflective color liquid crystal displays (LCDs) suffer from low luminance due to the inefficiency of reflecting ambient light, as individual RGB pixels require three sub-pixels, resulting in significant light loss and inability to produce a full RGB color spectrum with existing refractive index modulation techniques.

Innovation Solution

A reflective display apparatus utilizing a textured sub-micron metal film and a phase change material (PCM) layer, where the PCM switches between distinct phases to change the reflection properties of the metal film, enabling a larger refractive index modulation and color variation, thereby enhancing luminance and color capability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If individual RGB sub-pixels are used to achieve full color display, then color capability is improved, but luminance is reduced due to light loss from unused sub-pixels

Engineering Contradiction:

Improvecolor capabilityVSAvoidluminance

Core Design Contradiction:

Adaptability or versatilityVSIllumination intensity

Solution Approach 1:

The patent changes the refractive index parameter of the metal film by switching the PCM between phases, enabling a single sub-pixel to reflect different colors (RGB) by controlling the refractive index state, thus eliminating the need for multiple sub-pixels and improving luminance while maintaining full color capability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent utilizes phase transitions of the phase change material (PCM) between crystalline and amorphous phases to switch the reflection properties of the metal film. This phase transition mechanism enables dynamic color switching in a single sub-pixel, resolving the contradiction between color versatility and luminance

Inventive Principle:

Principle #36Phase transitions

2Adaptability or versatility

If LC layer is used to modify refractive index for color switching, then color variation is improved, but the shift in color is limited due to small refractive index change

Engineering Contradiction:

Improvecolor variationVSAvoidrefractive index modulation range

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The patent replaces the LC layer with a phase change material that undergoes phase transitions between crystalline and amorphous states, producing a much larger refractive index change (up to 0.5-1.0) compared to LC materials. This enables full RGB color spectrum production in individual sub-pixels while maintaining manufacturability through standard PCM fabrication processes

Inventive Principle:

Principle #36Phase transitions

Data Source

PatentUS11537002B1Full color reflective display including a phase change material

Publication Date: 2022.12.27 SHARP KK

AI summary

A reflective display apparatus is provided. The reflective display apparatus includes a textured sub-micron metal film textured in a periodic manner, a phase change material (PCM) layer, and a phase change control layer that is configured to change reflection properties of the textured sub-micron metal film by causing the PCM to switch between at least two of a plurality of phases.