LCD Offset Voltage Control for Burn-in Prevention
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Solution Overview
Problem
In liquid crystal display apparatuses with a vertical alignment mode and alignment division structure defined by alignment films, the formation of slits in pixel electrodes leads to DC deviation, causing burn-in due to flexoelectric polarization and variations in the applied voltage, which existing techniques fail to adequately address.
Innovation Solution
A liquid crystal display apparatus configuration where a control circuit generates a display signal voltage by adding a predetermined offset voltage to the original voltage, maintaining the offset voltage consistently for gray levels higher than or equal to a certain intermediate level, thereby minimizing DC deviation and preventing burn-in. This configuration involves a first and second alignment film defining different pretilt directions for liquid crystal domains and slits in the pixel electrode extending parallel to the tilted directions of these domains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If slits are formed in pixel electrode to reduce dark line width and improve transmittance, then transmittance is improved, but DC deviation occurs causing burn-in
Solution Approach 1:
The patent applies parameter changes by introducing a gray level-dependent offset voltage to compensate for DC deviation. Specifically, a first offset voltage is applied for gray levels below a threshold, and a second offset voltage (different from the first) is applied for gray levels at or above the threshold. This dynamic parameter adjustment compensates for the DC deviation caused by slits in the pixel electrode, preventing burn-in while maintaining the transmittance improvement.
2Reliability
If offset voltage is varied across all gray levels to compensate DC deviation, then burn-in is prevented, but polarity nonuniformity in effective voltage occurs
Solution Approach 1:
The patent applies local quality by differentiating the offset voltage application based on gray level regions. Instead of applying a uniform offset across all gray levels, the invention applies a first offset voltage to lower gray levels and a second offset voltage to higher gray levels (at or above a threshold). This localized approach compensates for DC deviation in the relevant gray level range while avoiding polarity nonuniformity in the effective voltage applied to the liquid crystal layer.
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 reduces the occurrence of burn-in caused by DC deviation, ensuring consistent voltage application across varying gray levels and minimizing the impact of flexoelectric polarization, thereby enhancing the display's durability and image quality.
Implementation Method 1
a plurality of liquid crystal domains having different reference alignment directions defined by the first and second alignment films
Implementation Method 2
By forming such slits, the width of a dark line occurring in a pixel can be reduced, resulting in an improvement in transmittance
Implementation Method 3
the formation of slits in pixel electrodes leads to DC deviation, causing burn-in due to flexoelectric polarization and variations in the applied voltage
Data Source
AI summary
A liquid crystal display apparatus includes: a liquid crystal display panel having a first substrate, a second substrate, and a vertical alignment type liquid crystal layer; and a control circuit configured to generate a display signal voltage. The first substrate has pixel electrodes to which the display signal voltage is applied, and a first alignment film. The second substrate has a counter electrode to which a common voltage is applied, and a second alignment film. Each pixel has liquid crystal domains having different reference alignment directions defined by the first and second alignment films. The pixel electrode has slits. The control circuit is configured to generate, as the display signal voltage, a voltage obtained by adding a predetermined offset voltage to an original voltage corresponding to a gray level. The offset voltage is substantially the same for gray levels higher than or equal to a predetermined intermediate gray level.