IPS LCD Insulation Layer Thickness for Chromaticity Shift
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Solution Overview
Problem
IPS LCD devices experience chromaticity shift and leakage light when viewed from a slanted angle due to differences in wavelength characteristics between normal and slanted viewing directions, which degrade image quality.
Innovation Solution
The IPS LCD device incorporates an insulation layer with a specific thickness relationship (d=(100+170×k)±30, where k is an integer from 0 to 5, and a refractive index of 1.8 to 2.0, sandwiched between substrates with lower refractive indices, to control transmittance and reduce chromaticity shift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an IPS LCD device uses a lateral electric field to rotate LC molecules for wider viewing angle, then viewing angle is improved, but chromaticity shift and leakage light occur in slanted viewing directions
Solution Approach 1:
The patent applies parameter changes by precisely controlling the thickness of the insulation layer to satisfy a specific mathematical relationship (d=(100+170×k)±30 nm). This thickness parameter modification changes the optical path difference and interference conditions, thereby suppressing chromaticity shift and leakage light while preserving the wide viewing angle characteristic of IPS LCD devices.
Solution Approach 2:
The insulation layer acts as an intermediary element between the substrate and the liquid crystal layer. By introducing this intermediate layer with specific optical properties (refractive index and thickness), the patent mediates the optical interaction to reduce harmful effects. The insulation layer functions as an optical compensator that modifies the overall optical characteristics of the LCD device.
2Object-affected harmful factors
If optical compensation layers are added to reduce leakage light and suppress chromaticity shift, then image quality is improved, but device complexity increases
Solution Approach 1:
The patent makes the insulation layer multi-functional by designing it to simultaneously serve as both an electrical insulation layer (for TFT operation) and an optical compensation layer (for reducing chromaticity shift and leakage light). This eliminates the need for separate optical compensation layers, thereby reducing device complexity while maintaining image quality.
Solution Approach 2:
The patent merges the function of the insulation layer with the function of an optical compensation layer. By combining these two functions into a single layer, the patent reduces the total number of layers and simplifies the device structure, while still achieving the desired optical performance improvement.
3Object-affected harmful factors
If the insulation layer thickness is increased to suppress chromaticity shift, then optical performance is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent segments the possible thickness values into discrete intervals defined by the formula d=(100+170×k)±30 nm, where k is an integer. This segmentation allows manufacturers to target specific thickness ranges rather than requiring precise control of a continuous variable, thereby reducing manufacturing precision requirements while still achieving the desired optical performance.
Solution Approach 2:
By defining the thickness parameter within specific intervals rather than as a single precise value, the patent transforms a high-precision parameter control problem into a lower-precision interval selection problem. This parameter change in the approach (from point value to interval range) significantly eases manufacturing requirements.
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 configuration effectively reduces leakage light and suppresses chromaticity shift between normal and slanted viewing directions, improving image quality by maintaining color accuracy across different viewing angles.
Implementation Method 1
the wavelength characteristic of the transmittance of the light is changed, due to the interference of light, depending on the thickness of the layer sandwiched between the layers having the lower refractive index
Implementation Method 2
the insulation layer 107 has an apparent thickness (d′) as observed in the slanted viewing direction, which is different from the thickness (d) thereof as observed in the normal viewing direction
Implementation Method 3
the LC layer 203 has a birefringence as viewed in the slanted viewing direction
Data Source
AI summary
An in-plane-switching-mode (IPS) LCD device includes a TFT substrate and a CF substrate sandwiching therebetween a liquid crystal (LC) layer, and a pair of polarizing films sandwiching therebetween the TFT and CF substrates and LC layer. The TFT substrate includes a SiNx insulation layer having a higher refractive index compared to the TFT substrate and LC layer. The thickness (d) of the SiNx layer is expressed by d=(100+170×k)±30 where k is an integer not smaller than zero and not larger than 5. The protective layer of the light-incident-side polarizing film near the insulation film has a thickness larger than zero and not larger than 57 μm.