Piezoelectric Touch Sensor Beneath Display for Visibility

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Solution Overview

Problem

Touch panels integrated into display devices often lead to a deterioration in transmittance and visibility, as they are typically placed on top of the display panel, affecting the surface brightness and image clarity.

Innovation Solution

A touch sensor configuration with a piezoelectric device and adhesive layer is placed on a substrate beneath the display unit, allowing the touch sensor to detect pressure without obstructing the display, using polysilicon for the piezoelectric device and signal lines, and an adhesive layer to attach substrates, enhancing adhesion and visibility.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a touch panel is provided on the display panel, then touch sensing function is enabled, but transmittance and visibility of the display panel deteriorate

Engineering Contradiction:

Improvetouch sensing functionVSAvoidtransmittance and visibility

Core Design Contradiction:

Adaptability or versatilityVSIllumination intensity

Solution Approach 1:

The touch sensor is moved from the front surface (2D plane on display) to the back surface (reverse side of display), changing its spatial dimension. This allows the touch sensing function to coexist with the display function without overlapping in the same optical path, thereby maintaining transmittance and visibility while enabling touch input detection

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Adaptability or versatility

If the touch sensor is disposed on the display panel, then touch input detection is enabled, but surface brightness and image clarity are reduced

Engineering Contradiction:

Improvetouch input detectionVSAvoidsurface brightness and image clarity

Core Design Contradiction:

Adaptability or versatilityVSIllumination intensity

Solution Approach 1:

Instead of placing the touch sensor on the front surface where it would block light, the sensor is inverted to the back surface of the display panel. This inversion allows light to pass through the display uninterrupted while still enabling touch detection through the piezoelectric effect that responds to pressure applied to the front surface

Inventive Principle:

Principle #13The other way round (Inversion)

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 improves the visibility and transmittance of the display by positioning the touch sensor beneath the display unit, preventing surface obstruction and maintaining image clarity while effectively detecting touch inputs.

Implementation Method 1

the touch sensor includes a piezoelectric device, which senses an external pressure

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS10540030B2Display device with touch sensing unit

Publication Date: 2020.01.21 SAMSUNG DISPLAY CO LTD

AI summary

A display device may include a first substrate, a touch sensor disposed on the first substrate, a second substrate disposed on the touch sensor, and a display unit disposed on the second substrate and which displays an image. The touch sensor includes a piezoelectric device, which senses a touch thereon, and an adhesive layer, which attaches the first and second substrates to each other. The piezoelectric device and the adhesive layer are disposed in a same layer.