Embedded Touch Display Using Ferroelectric Liquid Crystal
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Solution Overview
Problem
Embedded touch display devices using nematic liquid crystals in TN mode suffer from significant variations in permittivity due to large rotational angles, affecting the sensitivity of touch electrodes.
Innovation Solution
Replacing nematic liquid crystals with ferroelectric liquid crystals, such as Semi-V shaped or twisted ferroelectric liquid crystals, which exhibit smaller rotation angles and reduced permittivity variations, and using a capacitive touch unit with parallel driving and sensing electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If nematic liquid crystals in TN mode are used, then the liquid crystal panel can be manufactured with standard TFT LCD processing, but the large rotational angles cause significant variations in permittivity, affecting touch electrode sensitivity
Solution Approach 1:
The patent changes the material parameter from nematic liquid crystal to ferroelectric liquid crystal, which fundamentally alters the rotational behavior and permittivity characteristics. This parameter change resolves the contradiction by maintaining manufacturing compatibility while eliminating the large rotational angle-induced permittivity variations that degrade touch sensitivity.
Solution Approach 2:
The patent employs a composite structure combining ferroelectric liquid crystal with specific alignment layers and electrode configurations. This composite approach enables the system to leverage the advantages of ferroelectric materials (small rotation angles, stable permittivity) while maintaining compatibility with existing TFT LCD manufacturing processes.
2Adaptability or versatility
If separated touch screens are assembled by bonding touch panels and liquid crystal panels, then touch functionality can be added to display devices, but the device becomes thicker and light transmittance decreases
Solution Approach 1:
The patent merges the touch sensor functionality directly into the liquid crystal panel structure by using the liquid crystal layer itself as the sensing medium. This integration eliminates the need for separate touch panels and bonding processes, thereby reducing device thickness while maintaining touch functionality.
Solution Approach 2:
The liquid crystal layer serves dual functions: display function through standard TFT LCD operation and touch sensing function through capacitive detection. This multi-functionality eliminates the need for separate touch screen components, reducing overall device thickness and improving light transmittance.
3Adaptability or versatility
If multiple layers of glass and film are added for separated touch screens, then touch functionality is achieved, but light transmittance and contrast gradient are observably decreased
Solution Approach 1:
By merging the touch sensing function into the liquid crystal panel's existing layers, the patent eliminates multiple additional glass and film layers required for separate touch screens. This reduction in layers directly improves light transmittance and contrast gradient while preserving touch functionality.
Solution Approach 2:
The liquid crystal panel's existing structure and materials are made to serve dual purposes: display and touch sensing. The liquid crystal layer itself performs both optical modulation and capacitive sensing functions, eliminating the need for additional protective and functional layers that would reduce light transmittance.
4Ease of operation
If nematic liquid crystals with large rotational angles are used, then the liquid crystal can respond to touch input, but the significant variations in permittivity reduce touch electrode sensitivity
Solution Approach 1:
The patent changes the liquid crystal material parameter from nematic to ferroelectric type, which fundamentally alters the rotational characteristics. Ferroelectric liquid crystals exhibit small rotation angles with applied voltage, maintaining touch response capability while eliminating the large permittivity variations that degrade electrode sensitivity.
Solution Approach 2:
The patent leverages the inherent properties of ferroelectric liquid crystals that provide stable electrical characteristics during operation. This material choice ensures consistent permittivity throughout the touch detection process, maintaining high electrode sensitivity without requiring additional compensation mechanisms.
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
Improves the sensitivity and reliability of touch electrodes by minimizing parasitic capacitance effects, enhancing the overall performance and display quality of embedded touch display devices.
Implementation Method 1
the liquid crystal in the liquid crystal layer comprises Semi-V shaped ferroelectric liquid crystals, which are obtained by performing asymmetrical anchoring on the ferroelectric liquid crystal
Implementation Method 2
the push position can be determined by detecting an electromotive force generated when the ferroelectric liquid crystal is pushed
Implementation Method 3
the touch technology of the touch panel may be implemented by a capacitive touch control
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
An embedded touch display device includes a first substrate (100) and a second substrate (200) which are opposite; a liquid crystal display unit and a capacitive touch unit located between the first substrate and the second substrate. The liquid crystal display structure includes a pixel electrode layer (120), a common electrode layer and a liquid crystal layer (30), the pixel electrode layer (120) and the common electrode layer are located on two sides of the liquid crystal layer (30), and liquid crystal (30) in the liquid crystal layer (30) is ferroelectric liquid crystal. Nematic liquid crystal is replaced with ferroelectric liquid crystal in the embedded touch display device, thereby solving a problem that in a TN mode embedded touch display device, liquid crystal molecules rotate from a horizontal direction to a vertical direction or from a vertical direction to a horizontal direction, thus the rotational angle is large, which results a great variation of permittivity of the liquid crystal layer, and thus seriously affects the sensitivity effect of the touch electrodes.