Reflective Polarizer Mirror Display for Higher Rear-View Brightness

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Solution Overview

Problem

Conventional center rear view mirrors with display elements suffer from reflection losses due to non-polarization-dependent reflectors, leading to reduced brightness and efficiency, and require additional layers for mirror-like appearance.

Innovation Solution

Replacing at least one absorbing polarizer with a reflective polarizer in the display stack, allowing for ambient light reflection without additional layers, and using a liquid crystal cell with reflective polarizers adjacent to transparent substrate layers to create a reflective backlit display that enhances brightness and efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Shape

If a non-polarization-dependent reflector is used to create mirror-like appearance, then the mirror function is achieved, but reflection losses occur and brightness is reduced

Engineering Contradiction:

Improvemirror-like appearanceVSAvoidbrightness

Core Design Contradiction:

ShapeVSIllumination intensity

Solution Approach 1:

The patent changes the optical parameter of the polarizer from absorbing to reflective type, which fundamentally alters how light is handled. The reflective polarizer maintains polarization functionality while reflecting light back through the liquid crystal layer, thereby maintaining brightness and efficiency while achieving mirror-like appearance when the display is off.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent converts the previously harmful reflection loss into a beneficial feature. By using a reflective polarizer, the light that would have been lost is now reflected back through the liquid crystal layer, contributing to the mirror effect when the display is off while still enabling display functionality when activated.

Inventive Principle:

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

2Ease of operation

If absorbing polarizers are used in the display stack, then polarization control is achieved, but light is absorbed and brightness is reduced

Engineering Contradiction:

Improvepolarization controlVSAvoidbrightness

Core Design Contradiction:

Ease of operationVSIllumination intensity

Solution Approach 1:

The patent changes the operational parameter of the polarizer from absorption-based to reflection-based polarization control. The reflective polarizer achieves the same polarization function as absorbing polarizers but does so by reflecting light rather than absorbing it, thereby eliminating the brightness penalty associated with absorbing polarizers.

Inventive Principle:

Principle #35Parameter changes

3Shape

If additional layers are added to achieve mirror-like appearance, then the reflective function is improved, but device complexity increases

Engineering Contradiction:

Improvemirror-like appearanceVSAvoidnumber of layers

Core Design Contradiction:

ShapeVSDevice complexity

Solution Approach 1:

The patent makes the polarizer multi-functional by using a reflective polarizer that serves both as a polarization control element and as the mirror-like reflector. This eliminates the need for separate absorbing polarizers and additional mirror layers, reducing device complexity while maintaining both display and mirror functions.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent merges the function of the polarizer with the mirror function into a single component. The reflective polarizer combines polarization control and light reflection capabilities, eliminating the need for separate layers and reducing the overall complexity of the display stack.

Inventive Principle:

Principle #5Merging (Combining)

4Ease of operation

If absorbing polarizers are used, then polarization is controlled, but energy is lost and efficiency is reduced

Engineering Contradiction:

Improvepolarization controlVSAvoidlight absorption loss

Core Design Contradiction:

Ease of operationVSLoss of energy

Solution Approach 1:

The patent changes the energy interaction parameter of the polarizer from absorption to reflection. The reflective polarizer maintains polarization control functionality while changing the energy pathway from lossy absorption to non-lossy reflection, thereby eliminating energy loss and improving overall display efficiency.

Inventive Principle:

Principle #35Parameter changes

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 solution results in a higher brightness and more efficient reflective backlit display that maintains a mirror-like appearance while enabling the display of information without the need for extra layers, improving aesthetic appeal and functionality.

Implementation Method 1

a first reflective polarizer and a second reflective polarizer. The first and second reflective polarizers are each directly adjacent to one of the opposing transparent substrate layers

Methodology Applied

Scientific EffectPolarization: Polarisation

Data Source

PatentUS12065078B2Reflective backlit display with a liquid crystal cell

Publication Date: 2024.08.20 3M INNOVATIVE PROPERTIES CO

AI summary

Mirrors including reflective backlit displays are described. In particular, mirrors including backlit displays with a backlight, a liquid crystal cell including a liquid crystal layer disposed between two opposing transparent substrate layers, a first reflective polarizer, and a second reflective polarizer are described. The first and second reflective polarizers are each directly laminated to one of the opposing transparent substrate layers. Mirrors described herein may be configured as vehicle rear-view mirrors.