Bi-stable Display Stack-up for Mobile Devices

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Solution Overview

Problem

Current display stack-up configurations in clamshell mobile electronic devices are thick and power-intensive due to the use of multiple backlight units and larger internal displays, with external displays having lower visual information content and smaller active areas.

Innovation Solution

Implementing a bi-stable external display device with transmissive and reflective optical states, optically coupled with a single transparent backlight unit, and a high-resolution internal display, along with control circuitry to manage light distribution based on device position, reducing power consumption and thickness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If multiple backlight units are used to illuminate both internal and external displays, then illumination intensity is improved, but power consumption and device thickness increase

Engineering Contradiction:

Improvedisplay illuminationVSAvoidpower consumption

Core Design Contradiction:

Illumination intensityVSUse of energy by moving object

Solution Approach 1:

The external display device dynamically switches between reflective and transmissive optical states based on device usage conditions. In reflective state, ambient light is utilized reducing backlight power consumption. In transmissive state, the single backlight unit provides illumination. This dynamic switching resolves the contradiction by adapting illumination sources to actual needs.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The single backlight unit serves multiple functions: it illuminates the internal display directly and illuminates the external display when in transmissive state. The external display itself serves dual optical functions (reflective and transmissive modes). This multi-functionality eliminates the need for separate backlight units, reducing power consumption while maintaining illumination capability.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Illumination intensity

If multiple backlight units are sandwiched between displays, then illumination is sufficient, but device thickness increases

Engineering Contradiction:

Improvedisplay illuminationVSAvoiddevice thickness

Core Design Contradiction:

Illumination intensityVSLength of moving object

Solution Approach 1:

The patent merges the illumination function for both internal and external displays into a single backlight unit. The backlight unit is positioned to illuminate both displays sequentially or simultaneously depending on the optical state of the external display. This consolidation reduces the number of backlight units from two to one, directly reducing device thickness while maintaining adequate illumination.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The external display utilizes a different optical dimension by switching between reflective and transmissive states. In reflective state, it uses ambient light from the front; in transmissive state, it allows backlight illumination from behind. This dimensional switching capability allows a single backlight unit to suffice, eliminating the need for stacked backlight units and reducing thickness.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Area of stationary object

If external display has smaller active area, then device size is reduced, but visual information content decreases

Engineering Contradiction:

Improveexternal display areaVSAvoidvisual information content

Core Design Contradiction:

Area of stationary objectVSLoss of information

Solution Approach 1:

The patent applies different optical qualities to different usage scenarios. The external display, despite its smaller area, provides sufficient visual information for specific local functions (caller ID, notifications) when in reflective state. The internal display provides comprehensive visual information when the device is open. Each display's optical properties are optimized for its specific functional context, resolving the information content limitation.

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 optimizes power usage and thickness by dynamically switching the external display's optical state to reflect or transmit light, enhancing visual clarity and reducing energy consumption while maintaining effective information display in both open and closed positions.

Implementation Method 1

The optical states of the external display device include a transmissive optical state and a reflective optical state

Methodology Applied

Scientific EffectReflection: Reflection

Implementation Method 2

The external display device is placed in contact, and thus is optically coupled, with the backlight unit

Methodology Applied

Scientific EffectLight transmission: Light

Data Source

PatentUS7768605B2Display stack-up for a mobile electronic device having internal and external displays

Publication Date: 2010.08.03 GOOGLE TECHNOLOGY HOLDINGS LLC

AI summary

A display stack-up (300) is provided for a mobile electronic device (100) having an internal and external display, for example, a clamshell style mobile phone. The display stack-up comprises a backlight unit (114) and an external display device (110) having bi-stable optical states. The external display device (110) is placed in contact with, and is optically coupled to, the backlight unit (114). The display stack-up further comprises an internal display device (106) which is placed in contact with, and is optically coupled to, the external display device (110).