Block Copolymer Pressure-Sensitive Adhesive for Mobile Devices
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Solution Overview
Problem
Current pressure-sensitive adhesives used in mobile devices lack high bond strength, thermal shear strength, and shock resistance, particularly when exposed to mechanical stress and environmental factors, and often fail to release without leaving residue.
Innovation Solution
A pressure-sensitive adhesive formulation comprising 52% to 65% elastomer component, 30% to 45% adhesive resin, and 0% to 15% soft resin, with the elastomer component consisting of at least 90% polyvinylaromatic-polybutadiene block copolymers, including diblock and tri- or multiblock copolymers, optimized for high molecular weight and vinyl aromatic content to enhance bond strength, thermal shear strength, and shock resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a relatively high proportion of adhesive resin is added to achieve high bond strength, then bond strength is improved, but thermal shear strength and shock resistance deteriorate
Solution Approach 1:
The patent changes the chemical composition parameters of the adhesive formulation by incorporating specific block copolymers (polystyrene-polyisoprene and polystyrene-polybutadiene) with defined molecular weights and ratios. This compositional parameter change enables achieving bond strength ≥5.0 N/cm while simultaneously maintaining thermal shear strength ≥135°C and shock resistance ≥180 cm, resolving the contradiction between bond strength and reliability
Solution Approach 2:
The patent creates a composite adhesive system combining multiple polymer components (synthetic rubber, block copolymers, adhesives) in specific ratios. This composite formulation synergistically provides high bond strength through adhesive components while the block copolymer matrix ensures thermal and shock resistance, thus resolving the contradiction between bond strength and reliability
2Strength
If adhesive formulation is optimized for high bond strength and holding performance, then bonding performance is improved, but ease of removal without residue deteriorates
Solution Approach 1:
The patent utilizes the dynamic mechanical properties of block copolymers with low glass transition temperatures (polyisoprene: -60°C to -100°C, polybutadiene: -90°C to -110°C) that enable the adhesive to transition between bonded and removable states. The formulation achieves strong initial bonding through adhesive components while the elastomeric block copolymer matrix allows easy removal without residue under stretching, resolving the contradiction between bonding performance and ease of removal
3Strength
If adhesive resin content is increased to improve bond strength, then bond strength is improved, but processing behavior and rheological properties deteriorate
Solution Approach 1:
The patent optimizes the molecular weight parameters of block copolymers (Mw ≥80,000 g/mol for diblock, Mw ≥125,000 g/mol for tri- or multiblock) and their ratios in the formulation. This parameter optimization ensures adequate melt viscosity for processing while maintaining high bond strength, resolving the contradiction between bond strength and processing behavior
Data Source
Figure 1
AI summary
The invention relates to a block copolymer-containing pressure-sensitive adhesive comprising e) 52% by weight to 65% by weight, preferably 55% by weight to 62% by weight, of an elastomer component, f) 30% by weight to 45% by weight, preferably 35% by weight to 42% by weight, of at least one bonding resin, g) 0% by weight to 15% by weight, preferably to 10% by weight, of at least one softening resin and h) 0% by weight to 18% by weight, preferably to 10% by weight, of further additives, where the elastomer component (a) consists to an extent of at least 90% by weight of polyvinylaromatic-polybutadiene block copolymers, where the polyvinylaromatic-polybutadiene block copolymers include at least one type of diblock copolymer (a1) and at least one type of tri- or multiblock copolymer (a2), the at least one diblock copolymer (a1) has a vinylaromatic content of 15% by weight to 45% by weight, within the elastomer component (a) the proportion of tri- or multiblock copolymer (a2) is between 25% by weight and 50% by weight, preferably between 30% by weight and 45% by weight, the tri- or multiblock copolymer (a2) has a molar mass of at least 125 000 g/mol and a vinylaromatic content of 15% to 45% by weight, and one kind of the tri- or multiblock copolymer is preferably a multi-arm (radial) block copolymer.