Touch Screen Privacy Display With Switchable Liquid Crystal Retarder
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Solution Overview
Problem
Existing privacy displays lack electrically switchable off-axis privacy control and are limited to privacy functions, while touch screens do not integrate seamlessly with directional displays for enhanced privacy and stray light management.
Innovation Solution
A touch input display device incorporating a spatial light modulator (SLM), linear polarizers, a switchable liquid crystal retarder, and passive retarders, along with touch electrode arrays, allows for high contrast and luminance in wide viewing angles and low luminance for off-axis positions, enabling switchable privacy and stray light control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If micro-louvre optical films are used to provide privacy function, then off-axis luminance is reduced, but the display loses electrically switchable control capability
Solution Approach 1:
The patent applies dynamics by using a switchable liquid crystal retarder that can dynamically change its optical properties when voltage is applied. The liquid crystal molecules reorient in response to electric fields, enabling the display to switch between privacy mode (reduced off-axis luminance) and normal mode (full viewing angle) electrically, thus providing adaptability while maintaining privacy control capability
2Object-affected harmful factors
If contrast reduction is used to control off-axis privacy, then liquid crystal out-of-plane tilt is adjusted, but viewing angle flexibility is limited
Solution Approach 1:
The patent applies parameter changes by controlling the tilt angle of liquid crystal molecules through applied voltage. By adjusting the voltage magnitude, the liquid crystal out-of-plane tilt is precisely controlled, which modulates the off-axis luminance and contrast. This enables flexible privacy control while maintaining ease of operation through electrical parameter adjustment rather than mechanical constraints
3Object-affected harmful factors
If switchable backlights are used for luminance reduction, then off-axis luminance is controlled, but device complexity increases
Solution Approach 1:
The patent applies merging by integrating the privacy control function directly into the liquid crystal display layer itself, rather than using a separate switchable backlight system. The liquid crystal retarder is positioned between the backlight and the viewing side, combining the display and privacy control functions into a single integrated structure, thus reducing device complexity while achieving off-axis luminance reduction
4Adaptability or versatility
If touch electrode arrays are added to directional displays, then touch sensing capability is provided, but manufacturing cost and thickness increase
Solution Approach 1:
The patent applies universality by making the liquid crystal layer serve multiple functions simultaneously: it provides both the privacy control function (through its switchable optical properties) and the touch sensing function (by incorporating transparent conductive electrodes within the liquid crystal cell structure). This multi-functionality eliminates the need for separate touch screen layers, thereby reducing manufacturing cost and overall device thickness while maintaining full touch sensing capability
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 touch-sensitive display with high sensitivity, accuracy, and low lag, offering switchable privacy and stray light management with minimal thickness and cost, suitable for various optical systems.
Implementation Method 1
a switchable liquid crystal retarder comprising a layer of liquid crystal material arranged between the display polariser and the additional polariser, wherein the switchable liquid crystal retarder is a polar control retarder that is arranged, in a switchable state of the switchable liquid crystal retarder, simultaneously to introduce no net relative phase shift to orthogonal polarisation components of light passed by the display polariser along an axis along a normal to the plane of the switchable liquid crystal retarder and introducing a relative phase shift to orthogonal polarisation components of light passed by the display polariser along an axis inclined to a normal to the plane of the switchable liquid crystal retarder
Implementation Method 2
a display polariser arranged on the output side of the SLM, wherein the display polariser is a linear polariser; an additional polariser arranged on the output side of the display polariser, wherein the additional polariser is a linear polariser
Data Source
AI summary
A touch input display device includes a spatial light modulator (SLM), a display polariser, an additional polariser, a switchable liquid crystal retarder including a layer of liquid crystal material, switchable retarder control electrodes arranged to apply a voltage for controlling a state of the switchable liquid crystal retarder, at least one touch electrode array arranged in a layer on an output side of the switchable retarder control electrodes, and an output transparent support substrate where the at least one touch electrode array is arranged between the switchable retarder control electrodes and the output transparent support substrate.