Multilayer Film Warpage Control via Tg Parameter Optimization
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Solution Overview
Problem
Conventional multilayer films face challenges in suppressing warpage deformation, particularly after moisture and heat treatment, which affects their transparency, color tone, and appearance, while also being inadequate in terms of retardation and handling properties.
Innovation Solution
A method involving a multilayer film structure with specific glass transition temperature relationships between acrylic and aromatic polycarbonate resin layers, combined with controlled molding conditions, to achieve a film with improved transparency, color tone, and reduced retardation, while suppressing warpage deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a multilayer film is made by directly laminating acrylic resin layers and aromatic polycarbonate resin layer, then surface hardness and cutting processability are improved, but warpage deformation occurs after moisture and heat treatment
Solution Approach 1:
The patent applies parameter changes by precisely controlling the glass transition temperatures of the resin layers. Specifically, the aromatic polycarbonate resin layer is designed with Tg of 100-140°C, while the acrylic resin layers have Tg values that satisfy specific relational expressions (Tβ-Tα1)≤30 and (Tβ-Tα2)≤30. This temperature parameter optimization ensures coordinated thermal expansion and contraction behavior, preventing warpage while maintaining surface hardness and cutting processability.
2Stability of the object's composition
If conventional cooling roll methods are used to suppress warpage, then some warpage control is achieved, but the method is not fully satisfactory and transparency and color tone deteriorate
Solution Approach 1:
The patent replaces conventional cooling roll methods with a parameter-based approach that controls the glass transition temperatures of the resin layers. By optimizing Tg values to satisfy specific relational expressions, the film achieves dimensional stability without requiring aggressive cooling that would compromise transparency and color tone. This fundamental parameter optimization eliminates the need for post-processing cooling interventions.
3Illumination intensity
If the multilayer film structure is optimized for transparency, then light transmittance increases, but warpage deformation becomes more difficult to suppress
Solution Approach 1:
The patent resolves this contradiction by optimizing the glass transition temperature parameters of the resin layers. The aromatic polycarbonate resin layer is designed with Tg of 100-140°C, and the acrylic resin layers are configured to satisfy (Tβ-Tα1)≤30 and (Tβ-Tα2)≤30. This parameter optimization enables the film to maintain high light transmittance while achieving dimensional stability, as the coordinated thermal behavior prevents warpage without requiring opacity-increasing additives or structures.
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 method effectively reduces warpage deformation and enhances the multilayer film's transparency, color tone, and appearance, making it suitable for applications in image display devices with improved surface hardness and cutting processability.
Implementation Method 1
a glass transition temperature of an aromatic polycarbonate resin constituting the aromatic polycarbonate resin layer (β) is 100-140° C., and the following formulae (4-1) and (4-2) are satisfied: (Tβ−Tα1)≤30 (4-1) and (Tβ−Tα2)≤30 (4-2)
Data Source
AI summary
Embodiments provide a multilayer film, including: a first acrylic resin layer (α1), an aromatic polycarbonate resin layer (β), and a second acrylic resin layer (α2), where the first acrylic resin layer (α1), the aromatic polycarbonate resin layer (β), and the second acrylic resin layer (α2) are directly laminated in the stated order, where a glass transition temperature of an aromatic polycarbonate resin constituting the aromatic polycarbonate resin layer (β) is 100-140° C., and where the following formulae (4-1) and (4-2) and the following properties (i) and (ii) are satisfied: (Tβ−Tα1)≤30 . . . (4-1), (Tβ−Tα2)≤30 . . . (4-2), (i) a total light transmittance of the multilayer film is 85% or more, and (ii) a retardation of the multilayer film is 75 nm or less; and where Tai is a glass transition temperature of an acrylic resin constituting the first acrylic resin layer (α1), Tae is a glass transition temperature of an acrylic resin constituting the second acrylic resin layer (α2), and Tβ is a glass transition temperature of an aromatic polycarbonate resin constituting the aromatic polycarbonate resin layer (β), and all temperature units are ° C.