Vertical Alignment LCD Driving Waveform for Display Uniformity
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Solution Overview
Problem
Mono domain and multi domain vertical alignment type liquid crystal display devices face issues with display uniformity and transmissivity when the pretilt angle approaches 90°, leading to degraded performance and the formation of dark areas in the display.
Innovation Solution
Implementing a liquid crystal display apparatus with a driver apparatus that applies a specific driving waveform, such as waveform A, at a sufficiently high frame frequency to maintain display uniformity, particularly for pretilt angles between 88.5° and 89.9°, and using oblique electric field alignment control with high frequency components in the driving waveform to suppress dark area formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the pretilt angle is set close to 90° to improve alignment control, then the black level and alignment uniformity are improved, but the transmissivity decreases and dark areas form in the display
Solution Approach 1:
The patent applies periodic voltage reversal (frame reversal or N-line reversal) to switch the polarity of the driving waveform periodically. This periodic action prevents charge accumulation and ion migration that cause display non-uniformity, while maintaining the high pretilt angle configuration for good alignment control
Solution Approach 2:
The patent changes the driving parameters by using waveform A with specific duty ratios (1/16 to 1/64) and adjusting the frame frequency based on pretilt angle. This parameter optimization allows maintaining display uniformity while achieving high transmissivity with pretilt angles of 89.5° or more
2Manufacturing precision
If the frame frequency is increased to suppress dark area formation, then the display uniformity is improved, but the power consumption increases
Solution Approach 1:
The patent applies partial action by using N-line reversal where only every N lines reverse polarity, rather than full frame reversal. This reduces the frequency of polarity switching compared to complete frame reversal, thereby lowering power consumption while still effectively suppressing display non-uniformity and dark area formation
Solution Approach 2:
The patent optimizes the frame frequency parameter based on the pretilt angle to achieve the minimum necessary frequency for display uniformity, avoiding excessive frequency increases that would unnecessarily raise power consumption
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 approach effectively improves display uniformity and suppresses the formation of dark areas, maintaining a stable display state across various duty ratios and pretilt angles, thereby enhancing the electro-optic characteristics of the liquid crystal display devices.
Implementation Method 1
an electro-optic response of a liquid crystal display is determined by an effective voltage value
Implementation Method 2
liquid crystal molecules in a liquid crystal layer of a liquid crystal cell are aligned vertical to a substrate
Data Source
AI summary
A mono domain vertical alignment type liquid crystal display apparatus to be multiplex driven is provided whose display uniformity at a large pretilt angle (near 90°) is improved. Waveform A is applied to a liquid crystal cell of a mono domain vertical alignment type, the waveform A having a duty not lower than 4 and a frame frequency of f. The frame frequency f is determined from a pretilt angle θp, and is a frequency not lower than 60 Hz at a pretilt angle of 88.5°≦θp<89.6° or a frequency not lower than [120×(θp−89.6)+60] Hz at a pretilt angle of 89.6°≦θp≦89.9°.