NPEC Compensation Films for IPS LCD Light Leakage
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Solution Overview
Problem
In-plane switching (IPS) mode LCD devices experience light leakage due to retardation caused by stress applied to the display screen, particularly in normal black mode, leading to white spots when black is displayed.
Innovation Solution
The use of compensation films with negative photo-elastic constants (NPEC) is implemented outside the substrates to minimize retardation and prevent light leakage by combining layers with positive and negative photo-elastic properties without an intervening anisotropic medium, such as a liquid crystal layer, to counteract the photo-elastic effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a normal black type IPS mode LCD device is used, then wide viewing angle is achieved, but light leakage occurs when stress is applied to the display screen
Solution Approach 1:
The patent applies composite materials by combining compensation films with different photo-elastic constants (positive and negative) to create a multi-layer structure. This composite film structure compensates for stress-induced retardation in the glass substrate, preventing light leakage while preserving the wide viewing angle characteristics of IPS mode displays.
Solution Approach 2:
The patent changes the optical parameters of the compensation films by selecting materials with specific photo-elastic constants. By adjusting the thickness and material composition of each layer, the overall retardation compensation is optimized to counteract stress effects without compromising viewing angle performance.
2Ease of operation
If stress is applied to the display screen, then touch panel functionality is enabled, but retardation occurs causing white spots when black is displayed
Solution Approach 1:
The compensation films are pre-configured with specific photo-elastic properties to counteract the stress-induced retardation before it affects display quality. When stress is applied during touch operation, the compensation films generate opposing optical effects that prevent white spot formation, enabling touch functionality without compromising display uniformity.
3Strength
If glass substrates are used, then structural strength is provided, but photo-elastic effect causes retardation under stress
Solution Approach 1:
The compensation films act as intermediary elements between the glass substrates and the liquid crystal layer. These films mediate the optical effects by compensating for the photo-elastic retardation generated by the glass substrates under stress, allowing the use of strong glass materials without suffering from their photo-elastic drawbacks.
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 solution effectively reduces light leakage and maintains minimal luminance variations across viewing angles, improving the display quality by controlling retardation when stress is applied to the LCD device.
Implementation Method 1
at least one compensation film having a negative photo-elastic constant (NPEC) disposed outside at least one of the first and second substrates. The compensation film minimizes retardation of light when stress is applied to one of the first and second substrates.
Data Source
AI summary
Described herein is an LCD device in which retardation may be removed from a glass substrate when stress is applied to a display screen, thereby minimizing light leakage from the display screen. In the LCD device, a film having a negative photo-elastic constant (NPEC) is arranged to adjoin glass substrates so as to remove photo-elasticity. Specifically, in the LCD device, the NPEC films having negative photo-elasticity are respectively arranged at upper and lower sides of a liquid crystal cell, wherein the liquid crystal cell includes opposing glass substrates with a liquid crystal layer disposed therebetween.