Gel-like Resin Adhesive for Optical Module Thermal Stress
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Solution Overview
Problem
Existing optical modules with interference filters face spectral accuracy issues due to thermal expansion coefficient differences between substrates and fixing portions, leading to stress and distortion when exposed to large temperature changes.
Innovation Solution
An optical module design incorporating a gel-like resin adhesive layer between the interference filter and fixing portion, with specific thickness and Young's modulus conditions to alleviate shear stress, and a cured adhesive layer for enhanced fixation, ensuring high spectral accuracy across temperature variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the interference filter is fixed directly to the fixing portion using a conventional adhesive, then the adhesive strength is sufficient for normal conditions, but stress concentration occurs during large temperature changes causing distortion and spectral accuracy degradation
Solution Approach 1:
The patent uses a composite adhesive structure consisting of a gel-like resin layer (with high elasticity and stress absorption capability) combined with a cured adhesive layer (with strong bonding strength). This composite structure simultaneously achieves strong adhesion and stress relief during temperature changes, preventing distortion while maintaining adhesive strength.
Solution Approach 2:
The patent changes the physical and mechanical parameters of the adhesive material by selecting a gel-like resin with specific properties (high elasticity modulus, high elongation at break) that differ from conventional adhesives. This parameter change enables the adhesive to absorb thermal expansion stress while maintaining bonding, resolving the contradiction between strength and reliability under temperature variation.
2Strength
If a rigid adhesive is used to ensure strong bonding, then the adhesive strength is high, but the adhesive cannot absorb thermal expansion stress leading to distortion of the interference filter
Solution Approach 1:
The patent employs a gel-like resin layer that acts as a flexible intermediate film between the fixing portion and the interference filter. This flexible film can deform and absorb thermal expansion stress, preventing stress transmission to the interference filter that would cause distortion, while still maintaining adequate bonding strength.
Solution Approach 2:
The gel-like resin layer serves as a pre-established cushioning element that absorbs thermal expansion stress before it can reach the interference filter. This beforehand cushioning prevents distortion of the reflection films by accommodating dimensional changes during temperature variations.
3Reliability
If the adhesive layer is made thick to absorb stress, then stress absorption capability improves, but light loss increases due to absorption and scattering in the adhesive layer
Solution Approach 1:
The patent divides the adhesive function into two separate layers: a gel-like resin layer (5-20 μm thick) dedicated to stress absorption and a cured adhesive layer dedicated to bonding. This segmentation allows the stress-absorbing layer to be optimized for thinness (reducing light loss) while the bonding layer provides the necessary adhesive strength, achieving both stress absorption and minimal light loss.
Solution Approach 2:
The patent applies different material properties to different layers of the adhesive structure. The gel-like resin layer has high elasticity and is positioned to absorb stress, while the cured adhesive layer has strong bonding properties. This local differentiation of material quality allows each layer to perform its specific function optimally, with the thin gel layer minimizing light loss while effectively absorbing stress.
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 effectively suppresses distortion and maintains high spectral accuracy of the interference filter even in environments with large temperature changes, reducing light loss and enhancing adhesive strength between the filter and fixing portion.
Implementation Method 1
stress is generated due to a difference in the thermal expansion coefficients between the transparent substrate, the light receiving element or the like and the interference filter
Implementation Method 2
shear stress is applied to an adhesive layer disposed between the fixing portion and the interference filter
Implementation Method 3
an interference filter has been proposed which transmits or reflects only light of a predetermined wavelength from incident light
Data Source
AI summary
An optical module (colorimetry sensor) includes an interference filter, and a transparent substrate to which a first substrate of the interference filter is fixed, having a second thermal expansion coefficient which has a value different from a first thermal expansion coefficient. The interference filter is fixed to the transparent substrate through an adhesive layer made of gel-like resin, and the adhesive layer alleviates stress generated due to a difference in the thermal expansion coefficients between the interference filter and the transparent substrate.