Photocurable Adhesive Sheet Balancing Flexibility and Shape Stability
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Solution Overview
Problem
Adhesive sheets for flexible image display devices face challenges in achieving both high flexibility and shape stability while maintaining sensitivity to active energy rays.
Innovation Solution
An adhesive sheet composed of a (meth)acrylic copolymer that includes a monomer excited by active energy rays to generate active species, with specific storage shear modulus, strain values, and glass transition temperature properties, along with a mold release film, to enhance flexibility and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the adhesive sheet is made more flexible to satisfy flexible image display device requirements, then flexibility is improved, but sensitivity to active energy rays decreases and shape stability deteriorates
Solution Approach 1:
The adhesive sheet uses a composite polymer composition comprising a first polymer component and a second polymer component with different glass transition temperatures. The first polymer component (with Tg of -80°C to -20°C) provides flexibility and low-temperature performance, while the second polymer component (with Tg of 0°C to 100°C) provides shape stability and high-temperature resistance. This composite structure resolves the contradiction by combining materials with complementary properties.
Solution Approach 2:
The invention controls the glass transition temperature (Tg) distribution of the polymer composition by selecting polymers with specific Tg ranges and controlling their weight ratios. By adjusting the Tg parameters of the constituent polymers and their proportions, the adhesive sheet achieves optimal balance between flexibility (low Tg contribution) and shape stability (high Tg contribution).
2Ease of operation
If the adhesive sheet is made more flexible, then flexibility is improved, but sensitivity to active energy rays decreases
Solution Approach 1:
The composite polymer system incorporates photocurable functional groups in both polymer components, enabling the adhesive to maintain high sensitivity to active energy rays (UV or visible light) for curing. The first polymer provides flexibility while the second polymer enhances shape stability, and both contribute to photocurable functionality, resolving the contradiction between flexibility and curing sensitivity.
3Ease of operation
If the storage shear modulus at -20°C is increased to improve low-temperature flexibility, then flexibility is improved, but the maximum strain value increases excessively affecting shape stability
Solution Approach 1:
The invention precisely controls the storage shear modulus at -20°C to be within 10 kPa to 1,000 kPa by selecting polymers with appropriate Tg values and controlling their weight ratios. This parameter optimization ensures the adhesive remains flexible at low temperatures while preventing excessive strain deformation. The dual-polymer system allows independent optimization of low-temperature flexibility and high-temperature shape stability.
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 adhesive sheet exhibits high sensitivity to active energy rays, efficient curing, and excellent shape stability, with a mold release film ensuring easy removal and maintaining flexibility.
Implementation Method 1
a constitutional unit derived from a monomer M which is excited by irradiation with an active energy ray to generate an active species
Implementation Method 2
the adhesive composition containing a (meth)acrylic copolymer (A)... a constitutional unit derived from a monomer M which is excited by irradiation with an active energy ray to generate an active species
Data Source
AI summary
An adhesive sheet is formed of an adhesive composition containing a (meth)acrylic copolymer (A), in which the (meth)acrylic copolymer (A) has a constitutional unit derived from a monomer M which is excited by irradiation with an active energy ray to generate an active species