IPS LCD Driving Method Using Compensation Voltage
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Solution Overview
Problem
In-Plane Switching (IPS) mode LCD panels face limitations in brightness due to the aperture ratio reduction caused by pixel and common electrodes on the same substrate, leading to insufficient light transmission and slow response times, making it difficult to display moving images effectively.
Innovation Solution
A driving method for IPS mode LCD panels using a ferroelectric alignment film, where a compensation voltage is applied to reduce the rising and falling times of liquid crystal cells by over-driving or under-driving them, altering the alignment direction of liquid crystal molecules with an electric field oriented perpendicularly to the substrates, and employing ferroelectric liquid crystal polymer (FLCP) for faster response speeds and improved light transmittance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If pixel and common electrodes are formed on the same substrate in IPS mode LCD, then viewing angle is improved, but aperture ratio is reduced leading to insufficient brightness
Solution Approach 1:
The patent separates the pixel electrode and common electrode onto different substrates (upper and lower substrates respectively), transforming the electrode configuration from a single-plane arrangement to a three-dimensional distributed arrangement. This dimensional change allows both electrodes to be positioned without occupying the same physical space, thereby maintaining a high aperture ratio while preserving the IPS mode's wide viewing angle characteristics.
2Speed
If electrodes are formed on the same substrate, then transverse electric field is achieved for parallel liquid crystal movement, but light transmission is blocked reducing brightness
Solution Approach 1:
By positioning the pixel electrode on one substrate and the common electrode on the opposing substrate, the patent creates a three-dimensional electrode configuration that generates the necessary transverse electric field for IPS operation while minimizing light blocking. The spatial separation in the third dimension (thickness direction of the panel) allows light to pass through the liquid crystal layer more efficiently.
Solution Approach 2:
The patent employs thin film transistor (TFT) technology to create transparent or semi-transparent pixel electrodes that minimize light absorption and reflection. The thin film structure allows maximum light transmission while still providing the necessary electrical functionality for liquid crystal control.
3Device complexity
If conventional IPS driving method is used, then simple drive circuit is maintained, but response time is slow making moving image display difficult
Solution Approach 1:
The patent applies a compensation voltage before the main drive voltage to pre-align the liquid crystal molecules in the desired direction. This preliminary action reduces the time required for the liquid crystal to respond to the subsequent drive signal, thereby improving response speed without requiring complex drive circuits or additional hardware components.
Solution Approach 2:
The patent modifies the voltage application parameters by introducing a compensation voltage with specific magnitude and timing characteristics. This parameter change optimizes the liquid crystal's response behavior, enabling faster switching speeds while maintaining compatibility with conventional IPS drive circuit architectures.
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 method enhances the IPS mode LCD panel's ability to display images over a wider range of viewing angles with faster response speeds and improved contrast ratio by reducing the time required to achieve predetermined brightness levels, thereby addressing the issues of low brightness and slow response times.
Implementation Method 1
a first alignment film 26A and a second alignment film 26B may be formed of a material having molecules whose orientation can be altered in the presence of an electric field
Implementation Method 2
an electric field generated between first and second electrodes 24A and 24B may alter an orientation of FLCP molecules
Implementation Method 3
a liquid crystal layer 28 may be formed between the first and second alignment films 26A and 26B
Data Source
AI summary
A method of driving an IPS mode LCD includes applying a common voltage to a common electrode of the LCD panel, the LCD panel including a liquid crystal (LC) cell and driving the LC cell to express light at a predetermined brightness level associated with a predetermined data signal voltage applied to a pixel electrode, the driving including applying a compensation voltage to the LC cell prior to applying the predetermined data signal voltage, wherein a voltage difference between a previously applied data signal voltage and the compensation voltage is greater than a voltage difference between a previously applied data signal voltage and the predetermined data signal voltage.