Retardation Plate Nz Coefficient Optimization for LCD Viewing Angles
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Solution Overview
Problem
Liquid crystal displays (LCDs), particularly in the IPS mode, face challenges with viewing angle dependency due to the limited productivity and high cost of retardation plates with negative uniaxiality, which are necessary for improving viewing angle characteristics, and the limited types of resins that can be used for these plates.
Innovation Solution
Incorporating at least one retardation plate with negative uniaxiality and an optical axis in a plane direction between the liquid crystal cell and a polarizing plate in the LCD, where the Nz coefficient is between -1.0 and +0.2, and using uniaxially stretched polymers or liquid crystal discotic compounds to produce these plates, which can be easily integrated into the LCD structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a retardation plate with negative uniaxiality is used to improve viewing angle characteristics, then the viewing angle dependency is reduced, but the productivity decreases and cost increases
Solution Approach 1:
The patent changes the material parameters by using polymers with specific refractive index relationships (nx>ny and nx≈nz, or nz>nx>ny) and controlling the Nz coefficient within -1.0 to +0.2. This parameter optimization allows standard uniaxially stretched polymer films to achieve the desired optical compensation effect without requiring specialized negative uniaxiality materials, thereby improving productivity while maintaining viewing angle characteristics
Solution Approach 2:
The patent employs composite optical structures by combining the liquid crystal layer with retardation plates made from specific polymer compositions. The use of copolymers and terpolymers with carefully selected monomer ratios creates composite materials that exhibit the required optical properties, enabling mass production with conventional materials while achieving wide viewing angles
2Reliability
If a retardation plate with negative uniaxiality is used to improve viewing angle characteristics, then the viewing angle dependency is reduced, but the manufacturing cost increases
Solution Approach 1:
The patent optimizes optical parameters by selecting polymers with specific refractive index relationships and controlling the Nz coefficient range. This allows the use of conventional uniaxially stretched polymer films that can be manufactured using existing processes, avoiding the need for expensive specialized negative uniaxiality materials and reducing manufacturing costs while maintaining wide viewing angle performance
Solution Approach 2:
The patent replaces expensive, difficult-to-manufacture negative uniaxiality retardation plates with cheaper, easily manufactured uniaxially stretched polymer films. These standard polymer materials can be produced through conventional stretching processes, significantly reducing material costs and manufacturing complexity while achieving the same optical compensation function
3Ease of manufacture
If uniaxially stretched polymers are used to produce retardation plates, then the ease of manufacture improves, but the types of available resins are limited
Solution Approach 1:
The patent expands resin versatility by utilizing composite polymer systems including copolymers and terpolymers with various monomer combinations. By combining different polymer components with specific refractive index characteristics, the patent enables use of diverse resin types that can be processed through uniaxial stretching, thus increasing material selection flexibility while maintaining ease of manufacture
Solution Approach 2:
The patent creates universal applicability by developing a methodology that works with multiple polymer types (copolymers, terpolymers, and other polymers) through a common uniaxial stretching process. The specified refractive index relationships and Nz coefficient range serve as universal criteria that can be applied across different resin systems, enabling broad material selection without complicating the manufacturing process
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 enhances the viewing angle characteristics of LCDs by reducing light leakage across various angles, improving the display's performance without increasing production complexity or costs, and allowing for the use of more versatile polymer materials.
Implementation Method 1
at least one retardation plate placed between either one of said substrates and said polarizing plate arranged outside said substrate, wherein said at least one retardation plate has a negative uniaxiality and an optical axis in a plane direction
Data Source
AI summary
A liquid crystal display comprising a liquid crystal cell having a pair of substrates and a liquid crystal layer which is sandwiched between the pair of substrates and oriented substantially in parallel with the substrates in regions near the substrates in the absence of an applied voltage, a first polarizing plate arranged outside one of the substrates of the liquid crystal cell, a second polarizing plate arranged outside the other of the substrates of the liquid crystal cell, and at least one retardation plate placed between either one of the substrates and the polarizing plate arranged outside the substrate, in which at least one retardation plate has a negative uniaxiality and an optical axis in a plane direction thereof, and a Nz coefficient is from −1.0 to +0.2.