One-Sheet Polarizing Plate Crack Resistance via Modulus Ratios
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Solution Overview
Problem
One-sheet-type polarizing plates with triacetyl cellulose (TAC) films on one surface of the polarizer exhibit significant crack phenomena due to contraction and expansion, which is more pronounced than in two-sheet-type plates with TAC films on both surfaces.
Innovation Solution
A polarizing plate design with a specific ratio of tensile modulus and thickness of the polarizer and protective film, where the polarizer is bonded to a protective film with a polyethylene terephthalate (PET)-based film and a primer layer, optimizing the refractive indices and in-plane retardation to improve mechanical strength and reduce cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a TAC film is laminated on one surface of the polarizer in a one-sheet-type polarizing plate, then the structure is simplified and manufacturing is easier, but crack phenomenon occurs due to contraction and expansion of the polarizer
Solution Approach 1:
The patent uses a composite structure consisting of a polarizer layer and a polarizer protective film layer. The polarizer protective film is made from a specific polymer material with controlled physical properties (tensile modulus between 30-100 MPa, elongation at break between 15-30%) that forms a composite system capable of absorbing expansion forces and preventing crack propagation while maintaining manufacturing simplicity.
Solution Approach 2:
The patent controls specific physical parameters of the polarizer protective film to resolve the contradiction: tensile modulus is controlled within 30-100 MPa, elongation at break within 15-30%, and thickness within 5-20 μm. By optimizing these parameters, the film becomes sufficiently flexible to accommodate polarizer expansion without cracking, while remaining simple to manufacture.
2Strength
If the tensile modulus of the polarizer protective film is increased to improve strength, then mechanical strength improves, but the film becomes too rigid and cannot accommodate polarizer expansion
Solution Approach 1:
The patent precisely controls the tensile modulus of the polarizer protective film within the range of 30-100 MPa. This parameter optimization creates a balance where the film has sufficient mechanical strength to maintain structural integrity while remaining flexible enough to accommodate the expansion and contraction of the polarizer during temperature changes and manufacturing processes.
Solution Approach 2:
The patent applies a protective film with specifically tailored local mechanical properties (tensile modulus 30-100 MPa, elongation 15-30%) that matches the expansion characteristics of the polarizer. This localized optimization of mechanical properties allows the film to provide strength where needed while maintaining flexibility to accommodate dimensional changes.
3Reliability
If the thickness of the polarizer protective film is increased to prevent cracking, then crack resistance improves, but the overall thickness and device size increase
Solution Approach 1:
The patent optimizes the thickness of the polarizer protective film within the range of 5-20 μm. This thin-film design achieves adequate crack resistance through careful selection of material composition and mechanical properties (tensile modulus 30-100 MPa, elongation 15-30%) rather than relying on increased thickness, thereby maintaining a compact overall device structure.
Solution Approach 2:
The patent creates a composite system where a thin polarizer protective film (5-20 μm) with specially engineered mechanical properties provides sufficient crack resistance. The composite structure of the polarizer and protective film together achieves the required durability without needing excessive film thickness, maintaining device compactness.
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 improved design enhances the mechanical strength and reduces crack formation in the polarizing plate, thereby enhancing the polarization characteristics and durability of the display device.
Implementation Method 1
a crack phenomenon in a stretching direction, which is caused by the contraction and expansion of the polarizer
Implementation Method 2
a polarizer, which performs a polarization function
Data Source
AI summary
A polarizing plate includes: a bonding layer; a polarizer on a first surface of the bonding layer; and a polarizer protective film on a second surface of the bonding layer, and a ratio (β1/α3) of a measured tensile modulus (β1), in a transverse direction (TD), of the polarizing plate to a sum (α3) of a measured thickness (α1) of the polarizer and a measured thickness (α2) of the polarizer protective film is greater than 0.27 and less than 0.50, and a ratio (β2/β3) of a measured tensile modulus (β2), in the TD, of the polarizer to a measured tensile modulus (β3), in the TD, of the polarizer protective film is greater than 0 and less than 0.2.