Touch Panel Phase-Difference Plate for Sunglass Visibility

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Solution Overview

Problem

Conventional touch panels with polarizing plates cause visibility issues when users wear polarized sunglasses, especially in bright sunlight conditions, as the polarized sunglasses absorb light waves of the same direction as the polarized light emitted by the polarizing plate, making it difficult to recognize the LCD displays.

Innovation Solution

Incorporating a phase-difference plate with a ¼ wavelength on either the top surface of the upper substrate or the bottom surface of the lower substrate in the touch panel, which changes the polarization characteristics of the light, allowing it to exit with a phase-shift of ¼ wavelength, thereby maintaining visibility even when using polarized sunglasses.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If a polarizing plate is used in the touch panel to control light transmission, then the display visibility is improved under normal conditions, but the visibility deteriorates when users wear polarized sunglasses in bright sunlight

Engineering Contradiction:

Improvedisplay visibilityVSAvoidvisibility blockage by polarized sunglasses

Core Design Contradiction:

Illumination intensityVSObject-affected harmful factors

Solution Approach 1:

The patent applies a phase-difference plate with 1/4 wavelength to change the polarization state of light passing through the display. This modifies the optical parameters of the light beam, transforming linearly polarized light into circularly polarized light, which prevents complete absorption by polarized sunglasses and maintains display visibility under sunlight conditions.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent combines a polarizing plate and a phase-difference plate with 1/4 wavelength in the same optical path. This composite optical structure allows the polarizing plate to control light transmission for normal display operation while the phase-difference plate modifies the polarization state to prevent complete blockage by external polarized filters such as sunglasses.

Inventive Principle:

Principle #40Composite materials

2Illumination intensity

If a phase-difference plate with 1/4 wavelength is added to change light polarization, then visibility with polarized sunglasses is improved, but device complexity increases

Engineering Contradiction:

Improvevisibility with polarized sunglassesVSAvoidtouch panel structure

Core Design Contradiction:

Illumination intensityVSDevice complexity

Solution Approach 1:

The phase-difference plate with 1/4 wavelength is implemented as a thin film structure that can be integrated into the existing touch panel assembly. This thin-film approach minimizes additional thickness and structural complexity while achieving the required optical function of modifying light polarization state.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The phase-difference plate serves multiple functions: it modifies the polarization state of display light to prevent complete absorption by polarized sunglasses, maintains display visibility under various lighting conditions, and can be integrated with the existing polarizing plate structure. This multi-functionality reduces the need for separate components.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 provides a user-friendly input device with improved visibility and operability, ensuring that users can easily recognize the LCD displays even when wearing polarized sunglasses, enhancing usability in various electronic devices.

Implementation Method 1

a phase-difference plate with 1⁄4 wavelength is disposed on the top surface of the upper substrate or on the bottom surface of the lower substrate. By virtue of the phase-difference plate with 1⁄4 wavelength, lamplight that illuminates the LCD element undergoes the change of polarization characteristics

Methodology Applied

Scientific EffectPhase-difference plate effect: Birefringence

Implementation Method 2

polarizing plate 7 disposed on LCD element 8 absorbs Y-directional light wave perpendicular to X-directional light wave

Methodology Applied

Scientific EffectPolarization absorption: Polarisation

Data Source

PatentUS8189127B2Input device

Publication Date: 2012.05.29 PANASONIC HOLDINGS CORP

AI summary

According to the input device of the present invention, phase-difference plate (11) with ¼ wavelength is disposed on the top surface of upper substrate (1) of touch panel (12). As a result of passing through phase-difference plate (11), lamplight 9a that illuminates LCD element (8) goes outside as outgoing-light 9c with a phase-shift of ¼ wavelength. With the structure above, a user wearing polarized sunglasses—even if they have an absorption axis in a direction the same as that of lamplight 9a—can easily recognize the displays shown by LCD element (8) on the back surface of touch panel (12). The structure offers a user-friendly input device with good visibility of LCD element (8).