Photoconductive Touch LCD With Light Shielding Layer
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Solution Overview
Problem
Conventional touch screen technologies for LCDs, such as resistive and capacitive types, often reduce transmittance and brightness, and are vulnerable to external damage, while methods using optical sensors or capacitance detection increase production costs and decrease aperture ratio.
Innovation Solution
A liquid crystal display (LCD) with a touch screen function using a photoconductive material deposited between an insulating substrate and a light shielding layer, where photoconductive strips sense touch positions by varying current or voltage in response to external light, effectively preventing light leakage and enhancing signal detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional touch screen technologies (resistive or capacitive) are attached as modules to the outside of the display, then touch screen function is achieved, but transmittance is reduced and displayed images are degraded
Solution Approach 1:
The patent merges the touch sensing function with the existing pixel structure by integrating photoconductive materials into the pixel electrode or color filter layer, eliminating the need for separate external touch screen modules and maintaining high transmittance
Solution Approach 2:
The photoconductive material serves dual functions: as part of the pixel structure for display and as the sensing element for touch detection, allowing one component to perform multiple functions without adding external modules
2Reliability
If optical sensor devices such as photodiode or photo thin film transistor are placed in a pixel of panel, then touch detection is achieved, but aperture ratio decreases and transmittance is lowered
Solution Approach 1:
The patent changes the material parameter of the pixel electrode or color filter layer to photoconductive material, which changes its electrical conductivity in response to light, enabling touch detection without requiring additional sensor structures that would reduce aperture ratio
3Illumination intensity
If photoconductive material is deposited between insulating substrate and light shielding layer, then touch position detection is achieved with high transmittance, but light leakage may occur without proper light shielding
Solution Approach 1:
The patent introduces a light shielding layer as an intermediary component between the photoconductive material and the external environment, which blocks unwanted light while allowing the photoconductive material to detect touch-induced light variations, thus preventing light leakage without compromising transmittance
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 approach allows for effective touch position detection without reducing transmittance or brightness, simplifying construction and reducing production costs by eliminating the need for external optical devices, while offering flexible response times with various photoconductor materials.
Implementation Method 1
a photoconductive material is deposited between an insulating substrate provided in a color filter substrate of a liquid crystal panel and a light shielding layer so that a touch position can be effectively found by variation in current or voltage due to a change in characteristics of the photoconductor in response to light supplied from outside
Data Source
AI summary
Provided is a liquid crystal display (LCD) having a touch screen function using a photoconductor, which includes first and second substrates and a liquid crystal layer filled therebetween. The first substrate includes a touch sensing layer formed under a substrate and sensing a position by variation in current or voltage due to change in characteristics of the photoconductor in response to light supplied from outside, a light shielding layer formed under the touch sensing layer and preventing leakage of light, and a color filter layer including red (R), green (G) and blue (B) color filter patterns to express a color between the light shielding layer, thereby effectively finding a touch position according to a current variation depending on a change in characteristics of the photoconductor by the light supplied from outside.