Thermoforming Sheet with Matched Elongation to Reduce Layer Floating
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Solution Overview
Problem
Thermoforming sheets with hard coat layers face issues of floating protection films during handling and heat treatment, leading to appearance failures like wrinkles or scratches due to inadequate adhesion forces, which affect handleability and thermoformability.
Innovation Solution
A thermoforming sheet comprising at least three layers: a thermoplastic resin layer, an uncured (meth)acrylate-based active energy ray-curable resin layer, and a releasable layer, with specific elongation differences and release forces to minimize floating and enhance handleability and thermoformability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the adhesion force of the protection film to the hard coat layer is increased, then the protection film can be easily handled without floating, but the protection film cannot be easily released from the hard coat layer, deteriorating operating efficiency
Solution Approach 1:
The patent applies dynamics by making the adhesion force temperature-dependent. The protection film is designed to exhibit strong adhesion at low temperatures (room temperature) for easy handling and stacking, while showing weak adhesion at high temperatures (above glass transition temperature) for easy release. This temporal and conditional change in adhesion properties resolves the contradiction between maintaining strong adhesion and enabling easy release.
Solution Approach 2:
The patent changes the physical parameter of temperature to control adhesion force. By selecting a protection film with a specific glass transition temperature (Tg), the adhesion force transitions from strong (below Tg) to weak (above Tg). This parameter change allows the same film to satisfy both strong adhesion for handling and weak adhesion for release under different temperature conditions.
2Ease of operation
If the adhesion force of the protection film to the hard coat layer is weakened, then the protection film can be easily released, but the protection film substantially floats from the hard coat layer during stacking, causing appearance failures
Solution Approach 1:
The protection film's adhesion force dynamically adjusts based on temperature conditions during different process stages. During stacking and handling at room temperature, the film maintains strong adhesion to prevent floating. During release at elevated temperatures, the film exhibits weak adhesion for easy removal. This dynamic behavior eliminates the need to choose between strong and weak adhesion.
Solution Approach 2:
The patent utilizes the glass transition temperature (Tg) of the protection film as a critical parameter to control adhesion force. By designing the film with a Tg between -50°C and 150°C, the adhesion force naturally transitions from strong (below Tg) to weak (above Tg), enabling the film to prevent floating during handling while allowing easy release during heat treatment.
3Ease of operation
If a protection film is applied to the uncured hard coat layer, then handleability is improved, but the protection film may float during heat treatment causing wrinkles or scratches
Solution Approach 1:
The patent changes the temperature parameter during the process to control the adhesion state of the protection film. At room temperature during handling and stacking, the film exhibits strong adhesion to prevent floating and maintain appearance quality. During heat treatment, the temperature exceeds the film's Tg, causing the adhesion force to weaken and enabling easy release without causing wrinkles or scratches.
Solution Approach 2:
The protection film's adhesion properties are made dynamic through temperature variation. The film transitions from a high-adhesion state during handling to a low-adhesion state during heat treatment, allowing it to serve dual functions: protecting the surface during handling and enabling clean release during manufacturing.
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 sheet reduces or suppresses the occurrence of floating layers, ensuring excellent handleability and thermoformability while maintaining a smooth appearance, even after heat treatment.
Implementation Method 1
a layer (B layer) formed from an uncured product of a (meth)acrylate-based active energy ray-curable resin composition
Data Source
Figure 1
AI summary
It is to provide a thermoforming sheet which can be reduced or suppressed in the occurrence of floating of a releasable layer in stacking of a functional layer, a design layer, or the like, and which is excellent in handleability and thermoformability. A thermoforming sheet of the present disclosure is obtained by stacking at least three layers of a layer (A layer) comprising a thermoplastic resin, a layer (B layer) formed from an uncured product of a (meth)acrylate-based active energy ray-curable resin composition (composition B), and a layer (C layer) releasable from the B layer in the listed order, wherein β1 - α1 is -0.5% or more and 5.0% or less when a percentage of elongation in an MD direction at 100°C of the C layer is defined as β1 (%) and a percentage of elongation in an MD direction at 100°C of a stacked product obtained by releasing the C layer from the thermoforming sheet is defined as α1 (%).