Optical Element Bonding with Low Tg Resin to Reduce Warpage
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Solution Overview
Problem
The warpage of optical elements composed of glass substrates and resin lenses due to thermal expansion differences leads to degraded optical characteristics, particularly when the resin is on one side of the glass or when the glass is thin and the resin is thick, causing peeling issues with integrated optical filters.
Innovation Solution
An optical element with a glass substrate, an optical function portion made of resin, and a bonding portion with a glass transition point of 85° C. or lower and a Young's modulus of less than 100 MPa to reduce warpage caused by temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a laminate of glass substrate and resin lens is manufactured, then the optical element can be formed, but warpage occurs due to thermal expansion difference between glass and resin
Solution Approach 1:
A bonding portion made of resin material is introduced as an intermediary layer between the glass substrate and the optical function portion. This bonding portion acts as a stress buffer that absorbs thermal expansion differences between the glass substrate and the resin lens, preventing warpage while maintaining the structural integrity of the optical element.
Solution Approach 2:
The patent controls the thickness of the bonding portion as a critical parameter to manage warpage. By optimizing the bonding portion thickness to be within a specific range (0.1-1.0 times the glass substrate thickness), the thermal stress is effectively distributed, preventing both warpage and peeling issues.
2Volume of moving object
If the resin is present only on one side of the glass substrate, then the optical system can be compactified, but warpage becomes conspicuous
Solution Approach 1:
The bonding portion serves as a stress buffer that compensates for the asymmetric structure. Even though the resin optical function portion is only on one side, the bonding portion on both sides of the glass substrate balances the thermal stress distribution, preventing warpage in the compactified optical system.
3Volume of moving object
If the glass substrate is thin and the resin is thick, then the optical element can be made compact, but warpage is especially conspicuous
Solution Approach 1:
The patent establishes specific parameter relationships to control warpage in compact optical elements. The bonding portion thickness is set within a specific range (0.1-1.0 times the glass substrate thickness), and the glass substrate thickness is controlled (0.2-1.0 mm), creating an optimal parameter combination that prevents warpage even when the resin portion is thick.
4Manufacturing precision
If the optical filter is pasted all over the surface of the lens, then the lens and optical filter can be stacked, but the optical filter peels off due to volume expansion difference
Solution Approach 1:
Instead of uniformly pasting the optical filter across the entire lens surface, the patent applies the optical filter only to the optical effective region. The bonding portion extends beyond this region to provide additional bonding area, creating a local quality differentiation that ensures both stacking functionality and peeling 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 solution effectively minimizes warpage and peeling issues, maintaining optical integrity by adjusting the bonding properties to match the thermal expansion coefficients of the glass and resin, ensuring reduced aberrations and improved imaging quality.
Implementation Method 1
the bonding portion has a glass transition point of 85° C. or lower
Implementation Method 2
warpage occurs in accordance with a change in temperature due to a difference between the linear thermal expansion coefficient of the glass and the linear thermal expansion coefficient of the resin
Implementation Method 3
the bonding portion has a Young's modulus of less than 100 MPa
Data Source
AI summary
An optical element includes: a glass substrate; an optical function portion made of a resin; and a bonding portion that bonds the glass substrate and the optical function portion to each other. The bonding portion has a glass transition point of 85° C. or lower. The glass transition point of the bonding portion may be 50° C. or lower.