Anisotropic Scattering Sheet for Moiré Reduction in Anti-Eavesdropping Displays

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Solution Overview

Problem

Conventional display devices with anti-eavesdropping features suffer from significant moiré interference between pixels and anti-eavesdropping layers, leading to reduced display quality and inadequate eavesdropping prevention.

Innovation Solution

Incorporating a light-direction restricting element with alternating transparent and light-absorbing areas and an anisotropic scattering unit that scatters light more in the arrangement direction of moiré than in the first direction, reducing moiré visibility without compromising light directionality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a light-direction restricting element with alternating transparent and light-absorbing areas is used to increase display directivity and prevent eavesdropping, then eavesdropping prevention and display directivity are improved, but moiré interference increases and display quality deteriorates

Engineering Contradiction:

Improveeavesdropping preventionVSAvoidmoiré interference

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

An isotropic scattering layer is introduced as an intermediary between the light-direction restricting element and the display panel. This scattering layer diffuses light in all directions, interrupting the periodic pattern that causes moiré interference, while the light-direction restricting element maintains its function of controlling light transmission angles for eavesdropping prevention.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The scattering layer is positioned specifically at the interface where moiré interference occurs (between the light-direction restricting element and display panel), providing localized light diffusion exactly where needed to eliminate moiré patterns without affecting the overall light-direction restricting function.

Inventive Principle:

Principle #3Local quality

2Illumination intensity

If the width of transparent silicone rubber sheets is increased to improve parallel light transmittance, then transparency is improved, but the range of viewing angles increases which reduces eavesdropping prevention effectiveness

Engineering Contradiction:

Improveparallel light transmittanceVSAvoideavesdropping prevention

Core Design Contradiction:

Illumination intensityVSReliability

Solution Approach 1:

The width of transparent silicone rubber sheets is optimized to a specific range (100-200 μm, preferably 120-150 μm) to achieve the desired balance. This parameter adjustment ensures sufficient parallel light transmittance for display quality while maintaining narrow viewing angles for effective eavesdropping prevention.

Inventive Principle:

Principle #35Parameter changes

3Ease of operation

If the thickness of the anti-eavesdropping device is reduced to enable attachment to thin terminal devices, then ease of attachment is improved, but manufacturing precision and assembly difficulty increase

Engineering Contradiction:

Improveattachment to thin devicesVSAvoidassembly precision

Core Design Contradiction:

Ease of operationVSManufacturing precision

Solution Approach 1:

The anti-eavesdropping device is designed as a thin, layered structure where multiple functional layers (transparent silicone rubber sheets, colored silicone rubber sheets, adhesive layers) are nested together. This nested configuration achieves the required thinness for attachment to thin terminal devices while maintaining structural integrity through precise layer integration.

Inventive Principle:

Principle #7Nested doll (Nesting)

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 effectively reduces moiré interference while maintaining high display directivity and eavesdropping prevention, enhancing display quality and user comfort.

Implementation Method 1

a light-direction restricting element which is interposed in the path of the light incident on the display panel or the light exiting from the display panel, and which is provided with a plurality of transparent areas and a plurality of light-absorbing areas arranged in alternating fashion

Methodology Applied

Scientific EffectLight absorption: Absorption (EM radiation)

Implementation Method 2

anisotropic scattering unit for scattering incident light to a greater degree in the arrangement direction of moiré created between the display panel and the light-direction restricting element than in the first direction

Methodology Applied

Scientific EffectAnisotropic light scattering: Scattering

Data Source

PatentUS8339538B2Display device, terminal device, light source device, and optical member having a light-direction restricting element and a transparent/scattering state switching element

Publication Date: 2012.12.25 NEC CORP

AI summary

A display device comprising a light source and having an optical waveguide, a louver, an anisotropic scattering sheet, and a transmissive liquid crystal panel disposed along the path of light emitted from the light source. The light-restricting direction of the louver is tilted at an angle α from the Y-axis direction. The value of the angle α is set so that the arrangement direction of moiré created between the louver and the liquid crystal panel approaches the X-axis direction. A plurality of belt-shaped convex portions extending in the Y-axis direction are formed on the surface of the anisotropic scattering sheet, and are configured so that the scattering direction of the light has anisotropy. Specifically, scattering in the X-axis direction is increased, and scattering in the Y-axis direction is reduced. Moiré can thereby be reduced in a display device having increased directivity of the display.