Curable Adhesive Mixture for Heat-Sensitive Substrate Bonding
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Solution Overview
Problem
Conventional UV-curable structural bonding tapes exhibit high cold flow properties, leading to dimensional instability and requiring special storage and packaging, which complicates their use in applications where substrates are sensitive to heat.
Innovation Solution
A curable mixture comprising a first curable composition with a (meth)acrylate copolymer and a second curable composition with an epoxy resin and polyether polyol, which are sequentially cured using different wavelengths of actinic radiation, allowing for the formation of a pressure-sensitive adhesive that transitions to a structural adhesive, enabling bonding without heat exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional UV-curable structural bonding tapes are used, then curing without heat is achieved, but cold flow properties increase causing dimensional instability
Solution Approach 1:
The patent uses a composite adhesive system combining UV-curable acrylate components with heat-curable epoxy components. This composite formulation allows the adhesive to exhibit pressure-sensitive adhesive properties at room temperature with controlled cold flow, while achieving complete structural cure through sequential UV and heat treatment. The composite nature enables both low-temperature application and stable dimensional performance.
2Temperature
If conventional UV-curable structural bonding tapes are used, then heat-free curing is enabled, but special storage and packaging are required to maintain stability
Solution Approach 1:
The patent modifies the adhesive composition parameters by incorporating epoxy resins and hardeners in specific ratios, along with reactive diluents and initiators. This parameter optimization allows the adhesive to maintain stable properties at room temperature without requiring special storage conditions like refrigeration or protective atmospheres, while still enabling UV-curable application.
3Strength
If heat-curable structural adhesives are used, then strong bonding is achieved, but substrates susceptible to heat damage cannot be bonded
Solution Approach 1:
The patent segments the curing process into two distinct stages: first, UV-light curing to achieve initial bonding and positioning without heat exposure; second, optional heat curing to enhance bond strength. This segmentation allows substrates sensitive to heat to be bonded using only the UV-curing stage, while heat-sensitive applications can still benefit from the two-stage process if needed.
4Ease of operation
If UV-curable adhesives with high cold flow properties are used, then pressure-sensitive adhesive behavior is achieved, but dimensional stability during storage deteriorates
Solution Approach 1:
The patent creates local quality differentiation within the adhesive system by having different components cure at different rates and stages. The acrylate components provide initial pressure-sensitive adhesive behavior for easy application, while the epoxy components remain relatively uncured during storage, providing structural stability. This local quality differentiation between fast-curing and slow-curing components resolves the contradiction between ease of operation and storage 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 solution provides a curable mixture that maintains dimensional stability and can be printed or dispensed easily, bonding substrates effectively without heat, thus addressing the cold flow issues and substrate sensitivity challenges of conventional UV-curable adhesives.
Implementation Method 1
a free radical photoinitiator that is sensitive to actinic radiation of a first wavelength
Implementation Method 2
a photo-acid generator that is sensitive to actinic radiation of a second wavelength and that is not sensitive to actinic radiation of the first wavelength
Data Source
AI summary
A curable mixture, a partially cured composition, a cured composition, an article containing either the partially cured composition or the cured composition, and a method of bonding two substrates are provided. The partially cured composition functions as a pressure-sensitive adhesive while the cured composition functions as a structural or semi-structural adhesive. The curable mixture can be applied to a first substrate by printing or dispensing, if desired.