IPS Liquid Crystal Display Optical Film for Wide Viewing Angle
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Solution Overview
Problem
Conventional IPS mode liquid crystal displays suffer from narrow viewing angles due to optical leakage caused by the birefringence of triacetyl cellulose (TAC) films used in polarizing plates, which limits the realization of a wide viewing angle and high contrast ratio.
Innovation Solution
The use of optical films comprising polarizing plates and retardation films, where the absorption axis of the polarizing plate and the slow axis of the retardation film are perpendicular or parallel to each other, with specific refractive index and thickness conditions, to compensate for light leakage and enhance contrast across a wide range of viewing angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional polarizing plate with TAC protective film is used in IPS mode liquid crystal display, then the display achieves good black view in normal direction, but the viewing angle is narrowed due to optical leakage caused by birefringence of TAC film in oblique directions
Solution Approach 1:
A retardation film is introduced as an intermediary layer between the polarizing plate and the liquid crystal layer. This retardation film compensates for the phase difference caused by the TAC film's birefringence, thereby reducing optical leakage in oblique directions and expanding the viewing angle while maintaining black view quality
Solution Approach 2:
The optical film is constructed as a composite structure combining a polarizing plate with a retardation film having specific refractive index characteristics (Nz value between 0.3-0.7). This composite material approach allows the system to simultaneously achieve good black view and wide viewing angle by leveraging the complementary optical properties of the two materials
2Adaptability or versatility
If a retardation film is used as protective film for polarizer to compensate geometric axis shift, then some viewing angle improvement is achieved, but it is difficult to realize a sufficiently wide viewing angle in IPS mode liquid crystal display
Solution Approach 1:
The invention specifies precise parameter ranges for the retardation film, particularly the Nz value (nozzle parameter) between 0.3-0.7 and in-plane retardation Re between 200-300 nm. By optimizing these parameters, the retardation film effectively compensates for oblique viewing effects while maintaining high contrast ratio, achieving both wide viewing angle and reliable display quality
3Reliability
If the absorption axis of the polarizing plate and the slow axis of the retardation film are arranged perpendicular or parallel to each other with specific refractive index conditions, then light leakage is canceled and contrast ratio is improved, but the device structure becomes more complex
Solution Approach 1:
The polarizing plate and retardation film are merged into a single integrated optical film assembly with predetermined axis orientations (absorption axis perpendicular or parallel to slow axis). This merging simplifies the overall device structure by pre-configuring the optical components as a unit, reducing assembly complexity despite the increased functional integration
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 cancels light leakage in oblique directions, achieving a high contrast ratio and wide viewing angle, thereby improving the display quality of IPS mode liquid crystal displays.
Implementation Method 1
a retardation film with an Nz value represented by Nz=(nx1−nz1)/(nx1−ny1) in the range of from 0.3 to 0.7 and an in-plane retardation Re1=(nx1−nym1)×d1 in the range of from 200 to 300 nm
Implementation Method 2
optical leakage caused by characteristics of a polarizing plate in a direction shifted from an optical axis of the polarizing plates placed on upper and lower sides of the liquid crystal cell
Implementation Method 3
an absorption axis of the polarizing plate and a slow axis of the retardation film are perpendicular or parallel to each other
Data Source
AI summary
An IPS mode liquid crystal display comprising a liquid crystal cell, an optical film (F1) provided on a cell substrate on one side of the liquid crystal cell and comprises a polarizing plate comprising a transparent protective film having an in-plane retardation Re 10 nm or less and a thickness direction retardation Rth in the range of from 30 to 100 nm, a retardation film having an Nz value in the range of from 0.3 to 0.7 and an in-plane retardation Re1 in the range of from 200 to 300 nm, and an optical film (F2) provided on a cell substrate on the other side of the liquid crystal cell and comprises the polarizing plate and a retardation film having an Nz value in the range of from 0.9 to 1.2 and an in-plane retardation Re2 in the range of from 150 to 280 nm, and the absorption axes of the polarizing plates of the optical film (F1) and the optical film (F2) are perpendicular to each other, and both films are disposed so that the retardation film sides face the liquid crystal cell. The IPS mode liquid crystal display has a high contrast ratio across a wide range, and capable of realizing a better view.