Molding Resin Sheet Hard Coat Layering for Thermoforming Stability
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Solution Overview
Problem
Existing molding resin sheets face challenges in achieving high hardness while minimizing appearance abnormalities such as cracks and flow marks during molding, particularly during thermoforming, due to differences in glass transition points and melt viscosity between resin layers.
Innovation Solution
A molding resin sheet with a polycarbonate resin base material layer, a high-hardness resin layer between the base material and hard coat layers, where the high-hardness resin has a pencil hardness of HB or higher and a glass transition point relationship with the polycarbonate resin that ensures stability and reduces the likelihood of cracks and flow marks during thermoforming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a hard coat layer is provided directly on a polycarbonate resin base material, then surface hardness is improved, but appearance abnormalities such as cracks and flow marks occur during thermoforming
Solution Approach 1:
The patent divides the single hard coat layer into multiple layers with different functions: a first hard coat layer (softer, lower Tg) directly on the base material that provides flexibility during thermoforming, and a second hard coat layer (harder, higher Tg) on top that provides the desired surface hardness. This segmentation resolves the contradiction by allowing each layer to perform its specific function without interfering with the other.
Solution Approach 2:
The patent introduces a resin layer with specific glass transition point characteristics as an intermediary between the polycarbonate base material and the hard coat layer. This intermediate layer acts as a buffer that accommodates the thermal and mechanical stresses during thermoforming, preventing cracks and flow marks while still allowing the hard coat layer to achieve high surface hardness.
2Stability of the object's composition
If the glass transition point difference between resin layers is large, then each layer maintains its properties independently, but cracks and flow marks occur during thermoforming
Solution Approach 1:
The patent carefully controls the glass transition point parameters of each layer. The first hard coat layer has a Tg within 10°C of the base material to ensure compatibility and prevent cracking, while the second hard coat layer has a higher Tg to maintain hardness. This parameter optimization resolves the contradiction by finding the optimal balance between property stability and manufacturing quality.
3Strength
If a multilayer structure is used to improve hardness and reduce appearance abnormalities, then manufacturing complexity increases
Solution Approach 1:
The patent applies local quality by giving different properties to different layers: the first hard coat layer is formulated to be softer and more flexible, while the second hard coat layer is formulated to be harder and more rigid. This localized property differentiation achieves high overall hardness and defect reduction without requiring an excessively complex multilayer structure.
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 solution provides a resin sheet with enhanced hardness, reduced likelihood of appearance abnormalities, and improved thermoformability without compromising the hard coat's integrity, making it suitable for curved and complex shapes in applications like touchscreen displays and automotive components.
Implementation Method 1
the glass transition points of the polycarbonate resin (a1) and the high-hardness resin satisfy the following relationship: -10°C ≤ (Glass transition point of high-hardness resin) - (Glass transition point of polycarbonate resin (a1)) ≤ 40°C
Data Source
AI summary
According to an embodiment, provided is a molding resin sheet including: a base material layer containing a polycarbonate resin (a1); a high-hardness resin layer containing a high-hardness resin; and a hard coat layer, wherein the high-hardness resin layer is located between the base material layer and the hard coat layer, the high-hardness resin has a pencil hardness of HB or more, and the glass transition points of the polycarbonate resin (a1) and the high-hardness resin satisfy the following relationship: -10°C ≤ (the glass transition point of the high-hardness resin) - (the glass transition point of the polycarbonate resin (a1)) ≤ 40°C.