Optical Adhesive Sheet With Dual-Layer Tg Balance
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Solution Overview
Problem
Existing optical adhesive sheets for electronic devices, such as touch screen panels, face challenges in achieving both excellent step absorbency and weatherability, with current materials often compromising on one property for the sake of the other.
Innovation Solution
A layered optical adhesive sheet structure comprising a first adhesive layer with a glass transition temperature of −50° C. to −30° C. and a modulus of 0.3×105 Pa to 0.6×105 Pa, and a second adhesive layer with a glass transition temperature of −20° C. to −10° C. and a modulus of 0.7×105 Pa to 1.0×105 Pa, formed by curing specific acrylic resin compositions, to enhance step absorbency and weatherability respectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single adhesive layer with low glass transition temperature is used to achieve good step absorbency, then step absorbency is improved, but weatherability deteriorates
Solution Approach 1:
The adhesive sheet is divided into two distinct adhesive layers: a first adhesive layer with low glass transition temperature (−60°C to −40°C) for step absorbency, and a second adhesive layer with high glass transition temperature (0°C to 50°C) for weatherability. This segmentation allows each layer to independently optimize its function without compromising the other.
Solution Approach 2:
Different regions of the adhesive sheet (first and second adhesive layers) are assigned different material properties tailored to their specific functions. The first layer uses soft, low-Tg material for conforming to steps, while the second layer uses rigid, high-Tg material for environmental resistance.
2Reliability
If a single adhesive layer with high glass transition temperature is used to achieve good weatherability, then weatherability is improved, but step absorbency deteriorates
Solution Approach 1:
The adhesive sheet is divided into two distinct adhesive layers: a first adhesive layer with low glass transition temperature (−60°C to −40°C) for step absorbency, and a second adhesive layer with high glass transition temperature (0°C to 50°C) for weatherability. This segmentation allows each layer to independently optimize its function without compromising the other.
3Reliability
If adhesive composition with high crosslinking density is used to improve weatherability, then weatherability is improved, but step absorbency deteriorates
Solution Approach 1:
The adhesive sheet is divided into two distinct adhesive layers: a first adhesive layer with low glass transition temperature (−60°C to −40°C) for step absorbency, and a second adhesive layer with high glass transition temperature (0°C to 50°C) for weatherability. This segmentation allows each layer to independently optimize its function without compromising the other.
Solution Approach 2:
Different regions of the adhesive sheet (first and second adhesive layers) are assigned different material properties tailored to their specific functions. The first layer uses soft, low-Tg material for conforming to steps, while the second layer uses rigid, high-Tg material for environmental resistance.
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 layered structure effectively balances step absorbency and weatherability, allowing the optical adhesive sheet to absorb printing steps and withstand harsh conditions like high temperature and humidity, while maintaining processability and adhesiveness.
Implementation Method 1
the first adhesive layer has a glass transition temperature of about −50° C. to about −30° C. and a modulus of about 0.3×105 Pa to about 0.6×105 Pa
Implementation Method 2
the second adhesive layer has a glass transition temperature of about −20° C. to about −10° C. and a modulus of about 0.7×105 Pa to about 1.0×105 Pa
Implementation Method 3
The first adhesive layer may be formed by UV-curing the first adhesive composition. The second adhesive layer may be formed by thermally curing the second adhesive composition.
Data Source
AI summary
The present invention provides an optical adhesive sheet including a layered structure of a first adhesive layer and a second adhesive layer, in which the first adhesive layer has a glass transition temperature of −50° C. to −30° C. and a modulus of 0.3×105 Pa to about 0.6×105 Pa, and the second adhesive layer has a glass transition temperature of −20° C. to −10° C. and a modulus of 0.7×105 Pa to 1.0×105 Pa.