Optical Film with Tilted Inner Alignment for LCD Viewing Angle
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Solution Overview
Problem
Liquid crystal displays face challenges with viewing angle and light leakage due to the anisotropic refractivity of liquid crystals, particularly in vertical alignment modes, where existing compensation films cause degradation of contrast ratio by forming tilted alignment from the surface to the interior of the film.
Innovation Solution
A single optical film made of non-liquid crystalline thermoplastic resin with tilted alignment only in its inner part, formed without separate coatings, using a method that involves melt extrusion and passing the resin between rolls with controlled surface temperatures and shear forces to create different alignments on the surface and interior, thereby improving viewing angle and preventing light leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a compensation film with tilted alignment from surface to interior is used to improve viewing angle, then viewing angle is improved, but contrast ratio is degraded
Solution Approach 1:
The patent applies local quality by creating different alignment characteristics in different regions of the film. The surface region (0-10μm from surface) has no tilted alignment while the inner region (10-50μm from surface) has tilted alignment with a film β angle of 5-35°. This localized differentiation allows the surface to maintain good contrast ratio while the interior provides viewing angle compensation.
2Device complexity
If a single film structure is used to simplify manufacturing, then manufacturing complexity is reduced, but achieving both surface and interior alignment control becomes more difficult
Solution Approach 1:
The patent uses parameter changes by controlling the temperature distribution during the film forming process. The surface temperature is maintained below the glass transition temperature of the thermoplastic resin while the interior temperature is above the glass transition temperature, allowing different alignment states to be achieved in different regions of the single film.
Solution Approach 2:
The patent introduces temperature as an additional dimension of control in the film forming process. By creating a temperature gradient through the film thickness (surface cooler than interior), the process achieves spatially differentiated alignment control within a single film structure.
3Adaptability or versatility
If tilted alignment is formed from surface to interior to compensate for liquid crystals, then viewing angle is improved, but light leakage such as moiré occurs
Solution Approach 1:
The patent eliminates light leakage by ensuring the surface region (0-10μm) has no tilted alignment, while only the inner region (10-50μm) has tilted alignment for viewing angle compensation. This local differentiation prevents the surface from generating moiré patterns while maintaining the interior's viewing angle improvement function.
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 optical film significantly enhances viewing angle and prevents light leakage such as moiré in liquid crystal displays, while simplifying the manufacturing process and reducing costs by eliminating the need for additional coatings.
Implementation Method 1
melt extruding a non-liquid crystalline thermoplastic resin; and passing the melt extruded thermoplastic resin between a first roll and a second roll to form a film
Implementation Method 2
impart a tilt angle to an inner part of the film by generating different shear force on a surface of the film and in an interior of the film depending on operation of the first and second rolls
Implementation Method 3
the first and second rolls have a surface temperature less than a glass transition temperature of the thermoplastic resin
Implementation Method 4
generating different shear force on a surface of the film and in an interior of the film depending on operation of the first and second rolls
Data Source
AI summary
Disclosed are an optical film, a method for preparing the same, and a liquid crystal display including the same. The optical film is a single film of a non-liquid crystalline thermoplastic resin, and includes: first and second surface part placed on both surfaces of the film in a thickness direction; and an inner part of the film placed between the first and second surface part, wherein the first and second surface part are not aligned with a tilt in the thickness direction, and the inner part of the film is aligned with a tilt in the thickness direction.