Release Film Modulus Tuning for Thermoformable PSA Laminate Sheets
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Solution Overview
Problem
Pressure-sensitive adhesive (PSA) sheets applied to non-flat surfaces face issues such as wrinkling during application and damage to release liners during thermoforming, leading to appearance defects and reduced reliability.
Innovation Solution
A laminate sheet with a release film having a Young's modulus between 500 MPa and 500 MPa or less, formed from a solvent-based thermally curable addition-reaction type silicone release agent, allows for easy thermoforming and controlled peel strength, preventing damage and partial lifting of the release film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a general release-lined PSA sheet is molded by hot-pressing into a non-flat shape, then the PSA sheet can be applied to non-flat surfaces, but the release liner may suffer damage such as tearing due to the load during thermoforming
Solution Approach 1:
The invention changes the physical parameters of the release film by controlling its Young's modulus at different temperatures. The release film has a Young's modulus of 50 MPa or less at 100°C, making it sufficiently soft and flexible during thermoforming to conform to non-flat surfaces without tearing, while maintaining adequate strength at room temperature for handling and application.
Solution Approach 2:
The invention applies different mechanical properties to the release film at different temperature conditions. At processing temperature (100°C), the film exhibits low stiffness (50 MPa or less) for easy deformation, while at room temperature it has higher stiffness for structural integrity. This temperature-dependent local quality resolution allows the same material to satisfy conflicting requirements under different conditions.
2Adaptability or versatility
If a release-lined PSA sheet is molded by hot-pressing into a non-flat shape, then the PSA sheet can be applied to non-flat surfaces, but after thermoforming or with subsequent aging, the release liner may partially lift from the adhesive face, causing appearance defects and lowering reliability
Solution Approach 1:
The invention utilizes temperature-dependent parameter changes in the release film's Young's modulus. At 100°C during thermoforming, the modulus is 50 MPa or less allowing easy deformation and conforming to non-flat surfaces. At room temperature (20°C), the modulus increases to 200 MPa or more, providing sufficient stiffness to prevent partial lifting and maintain reliable adhesion stability during storage and application.
Solution Approach 2:
The release film exhibits dynamic mechanical properties that change with temperature. The film transitions from a soft, easily deformable state at processing temperature to a stiffer, more stable state at room temperature. This dynamic behavior allows the film to be easily molded when heated while maintaining structural integrity and preventing lifting when cooled, resolving the contradiction between formability and adhesion stability.
3Strength
If the Young's modulus of the release film at 120°C is high, then the release film maintains strength, but the laminate sheet becomes difficult to thermoform and the release film may be damaged during molding
Solution Approach 1:
The invention exploits parameter changes with temperature by designing a release film with a Young's modulus of 500 MPa or less at 120°C, making it sufficiently soft for easy thermoforming and molding into non-flat shapes without damage. The film's low modulus at processing temperature ensures high ease of manufacture while maintaining adequate strength through controlled material composition and thickness.
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 laminate sheet enables reliable application of PSA sheets to non-flat surfaces by maintaining the integrity of the release film, ensuring smooth thermoforming and adherence to the adherend without defects.
Implementation Method 1
a release layer provided at least to the PSA body side surface of the resin film... The release layer is formed from a solvent-based thermally curable addition-reaction type silicone release agent
Implementation Method 2
a release layer provided at least to the PSA body side surface of the resin film... The release layer is formed from a solvent-based thermally curable addition-reaction type silicone release agent
Implementation Method 3
to facilitate application while preventing wrinkling during the application, a double-faced PSA sheet premolded to have the corresponding non-flat shape be applied to the adherend
Implementation Method 4
When a general release-lined PSA sheet in flat form is molded by the sort of hot-pressing into a non-flat shape
Implementation Method 5
pressure-sensitive adhesive (PSA) exists as a soft solid (a viscoelastic material) in a room temperature range and has a property to adhere easily to an adherend with some pressure applied
Data Source
Figure 1~2
Figure 3~4
AI summary
This invention provides a laminate sheet with release film laminated to an adhesive face that is highly thermoformable and suitable for use in an application where after pre-thermoformed, the release film is removed and the adhesive face is applied to an adherend. Provided is a laminate sheet comprising a sheet of a PSA body as well as first and second films laminated on first and second faces of the PSA body. The second film comprises a resin film and a release layer provided at least to the PSA body side surface of the resin film while satisfying the following conditions: having a Young's modulus at 85 °C of 500 MPa or greater, and having a Young's modulus at 120 °C of 500 MPa or less.