Optical Film Tilt Structure for TN-Mode Display Compensation
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Solution Overview
Problem
Conventional optical films for TN-mode liquid crystal display devices fail to achieve sufficient viewing angle compensation and suffer from peripheral unevenness issues, such as light leakage, due to inadequate internal structure and production methods.
Innovation Solution
An optical film with a specific internal structure is produced by leading a thermoplastic resin melt between nip-pressing surfaces and laterally stretching it within a temperature range of (Tg−40)° C. to (Tg+5)° C., where the slow axis direction differs from the film tilt direction, and the birefringence varies in the thickness direction, optimizing the angle between slow axis and tilt directions and the distribution of retardation values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a shearing force is imparted to a solid film to create a tilt structure, then the optical axis in the thickness direction becomes tilted, but the uniformity of optical properties deteriorates
Solution Approach 1:
The invention changes the physical state parameter of the material from solid to melt during the shearing process. By imparting shearing force to a melt rather than a solid film, the material can be more uniformly deformed, creating a consistent tilt structure throughout the film thickness while maintaining uniform optical properties.
Solution Approach 2:
The invention utilizes the phase transition of the material from solid to melt state. The material is heated above its melting point during the tilt structure formation process, allowing for uniform molecular orientation under shear stress, and then cooled to solidify the tilted structure uniformly throughout the film.
2Ease of manufacture
If an optical film with a tilt structure is stretched in the machine direction, then the film can be processed, but the internal structure becomes insufficient for adequate viewing angle compensation
Solution Approach 1:
The invention inverts the conventional approach by first creating the tilt structure through shearing in the melt state, and then performing stretching in the solid state. This reversed sequence allows the tilt structure to be established before stretching, ensuring that the internal structure maintains its integrity and provides adequate viewing angle compensation while still allowing for necessary film processing.
Solution Approach 2:
The invention performs the tilt structure formation as a preliminary action before stretching. By establishing the tilted molecular orientation in the melt state first, and then solidifying and stretching the film, the internal structure is pre-configured to provide the necessary optical compensation properties that are maintained through the subsequent stretching process.
3Productivity
If conventional optical films are used in TN-mode liquid crystal display devices, then the devices can be manufactured, but peripheral unevenness such as light leakage occurs
Solution Approach 1:
The invention creates a position-dependent optical structure where the tilt angle and birefringence vary through the film thickness. This local variation in optical properties is specifically designed to compensate for the viewing angle-dependent phase differences that cause peripheral unevenness and light leakage in TN-mode display devices.
Solution Approach 2:
The invention creates a composite optical structure within the film by combining regions with different tilt angles and birefringence values through the thickness. This internal composite structure, with its gradient of optical properties, provides viewing angle compensation that eliminates peripheral unevenness while maintaining manufacturability.
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 resulting optical film enhances viewing angle compensation and reduces peripheral unevenness in TN-mode liquid crystal display devices, providing improved optical properties and stability.
Implementation Method 1
leading a thermoplastic resin melt between nip-pressing surfaces
Implementation Method 2
leading a thermoplastic resin melt between nip-pressing surfaces
Implementation Method 3
laterally stretching it
Implementation Method 4
the birefringence varies in the thickness direction
Data Source
AI summary
An optical film comprising a thermoplastic resin, which is such that the slow axis direction in the film plane differs from the film tilt direction and the birefringence of a sliced section of the film that contains the tilt direction and the thickness direction in the plane varies in the thickness direction of the film.