Reflective LCD with Retardation Layer for In-Cell Touch Contrast
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Solution Overview
Problem
Current reflective liquid crystal display devices with a transverse electrical field mode, such as FFS mode, have low reflectance, leading to a decreased contrast ratio, making them unsuitable for use as in-cell type touch panels capable of reflection mode display.
Innovation Solution
A liquid crystal display device configuration that includes a first substrate with a reflective layer and electrodes generating a transverse electrical field, a liquid crystal layer with twist alignment, a second substrate, a retardation layer comprising a λ/4 plate, a λ/2 plate, and a positive C plate, and a polarizer, optimized to improve contrast ratio and viewing angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a transverse electrical field mode (FFS mode) is used in a reflective liquid crystal display device, then the device structure is simplified with electrodes only on the active matrix substrate side, but the reflectance becomes low (approximately 60% of VA mode), causing decreased contrast ratio
Solution Approach 1:
The patent changes the electrical field configuration parameter from transverse (FFS mode) to vertical (VA mode), which fundamentally alters the liquid crystal molecule orientation and optical properties. This parameter change enables the liquid crystal layer to achieve higher reflectance while maintaining the simplified electrode structure where only the active matrix substrate side has electrodes.
2Ease of manufacture
If a transverse electrical field mode is adopted for reflective liquid crystal display, then manufacturing is simplified, but the contrast ratio decreases due to low reflectance
Solution Approach 1:
The patent changes the operating mode parameter from transverse electrical field (FFS) to vertical electrical field (VA), which improves the reflectance and contrast ratio while maintaining manufacturing simplicity. The VA mode utilizes the natural orientation of liquid crystal molecules perpendicular to the substrate plane, achieving better optical performance without complex manufacturing processes.
3Length of moving object
If in-cell type touch panel is implemented with reflective display capability, then frame narrowing and thickness reduction are achieved, but such a panel has not yet been realized due to low reflectance in transverse mode
Solution Approach 1:
The patent changes the electrical field mode parameter from transverse to vertical, enabling the in-cell type touch panel to achieve sufficient reflectance for practical use. This parameter change allows the thin-panel structure to maintain both its thickness advantages and adequate optical performance for reflective display applications.
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 proposed configuration enhances the contrast ratio and viewing angle of the liquid crystal display device, making it suitable for use as an in-cell type touch panel capable of performing display in a reflection mode at a lower cost.
Implementation Method 1
liquid crystal display devices, which utilize a liquid crystal material to function as a display device
Implementation Method 2
the first substrate includes a reflective layer that reflects light
Implementation Method 3
the retardation layer includes a λ/4 plate, a λ/2 plate, and a positive C plate
Data Source
AI summary
A liquid crystal display device includes a first substrate, a liquid crystal layer, a second substrate, a retardation layer, and a polarizer in this order from a back face side, and includes a plurality of pixels arrayed in a matrix shape, in which the first substrate includes a reflective layer that reflects light, a first electrode and a second electrode that are capable of generating a transverse electrical field in the liquid crystal layer, and a first horizontal alignment film that is in contact with the liquid crystal layer, the second substrate includes a second horizontal alignment film in contact with the liquid crystal layer, the liquid crystal layer has a twist alignment when no voltage is applied, and the retardation layer includes a λ/4 plate, a λ/2 plate, and a positive C plate.