Transflective LCD Inverting Drive Scheme for Mode Matching
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Solution Overview
Problem
Transflective LCD devices employing lateral-direction-electric-field modes face issues with inverted display states between reflective and transmissive areas, leading to mismatched image quality in reflective and transmissive modes.
Innovation Solution
The implementation of an inverting drive scheme that adjusts drive voltages and electrode configurations to match the reflectance and transmittance characteristics between reflective and transmissive areas, ensuring synchronized dark-state and bright-state setups in both modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a transflective type LCD device employs lateral-direction-electric-field mode (IPS or FFS) with a single common electrode, then the device structure is simplified and manufacturing is easier, but the display states (black and white) become inverted between reflective and transmissive areas
Solution Approach 1:
The common electrode is segmented into a first common electrode for the reflective area and a second common electrode for the transmissive area. This segmentation allows independent voltage control of each area, enabling separate optimization of display characteristics and correction of the inverted display state issue without complicating the overall device structure
Solution Approach 2:
Different common electrodes are provided for different display areas (reflective and transmissive) to achieve locally optimized display characteristics. The first common electrode is optimized for reflective mode while the second common electrode is optimized for transmissive mode, allowing each area to have the appropriate electrical characteristics for its specific function
2Device complexity
If the reflective area and transmissive area share the same common electrode and cell gap, then device complexity is reduced, but the voltage-luminance characteristics and image quality become mismatched between the two modes
Solution Approach 1:
The common electrode is divided into separate first and second common electrodes for reflective and transmissive areas respectively. This enables independent voltage control and optimization of each area's electrical characteristics, allowing matching of voltage-luminance characteristics between modes
Solution Approach 2:
Different cell gaps are established in the reflective area and transmissive area through the segmented common electrode structure. By adjusting the cell gap parameter independently in each area, the optical characteristics and voltage-luminance curves can be optimized to match between reflective and transmissive modes
3Manufacturing precision
If separate common electrodes are provided for reflective and transmissive areas, then image quality and voltage-luminance characteristics can be matched between modes, but device complexity and manufacturing complexity increase
Solution Approach 1:
The common electrode is segmented into first and second common electrodes that can be formed using the same manufacturing process steps as the pixel electrodes. This segmentation approach maintains manufacturing simplicity while achieving the benefit of independent voltage control and matched image quality between modes
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 enables the image quality in reflective mode to match the image quality in transmissive mode, resolving the issue of inverted display states and improving overall display performance.
Implementation Method 1
The LCD device of the lateral-direction-electric-field mode such as the IPS mode and FFS mode has a pixel electrode and a common electrode which are formed on the same substrate, and applies an electric field of the lateral direction to an LC layer
Implementation Method 2
Due to the configuration wherein the LCD device of the lateral-direction-electric-field mode displays an image by rotating LC molecules in a direction parallel to the substrate
Implementation Method 3
The reflective area has a reflection film, and the light incident from the outside and reflected by the reflection film is used as a display light source
Implementation Method 4
The transmissive area transmits light from a backlight source, and sets the backlight source as a display light source
Implementation Method 5
A polarizing film (first polarizing film) 51 on the viewer side, or front side, and a polarizing film (second polarizing film) 52 on the rear side are arranged such that the polarizing axes thereof are perpendicular to each other
Data Source
AI summary
An LCD device has a reflective area that reflects light incident from a polarizing film side using a reflection film, and a transmissive area that transmits light of a backlight incident from a TFT substrate side. The drive voltages of the reflective area and transmissive area are Vr and Vt, the black voltage in the reflective area is Vr (K), the black voltage in the transmissive area is Vt (K). The reflectance R, the transmittance T, characteristics of R with respect to drive voltage [Vr (K)−Vr] and characteristics of T with respect to drive voltage [Vt−Vt (K)] substantially match each other.