Plastic Glass Mirror Frame Structure for Distortion Control
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Solution Overview
Problem
Conventional rearview mirrors for automotive vehicles face issues with distortion and vibration in plastic glass mirrors due to cooling effects and ejection pin-induced distortions, as well as interference from hard coating layers, which affect the optical quality and reliability of the mirror image.
Innovation Solution
A plastic glass mirror design that incorporates a frame structure in the moulding tool to slow down cooling and minimize distortion, combined with optimized metallization and hard coating processes, including a specific thickness and radius for the frame and hard coat layers, and a unique heater design with a C-shaped resistive layer for even current distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If plastic glass is used to replace silica glass in rearview mirrors, then weight is reduced and safety is improved, but distortion and vibration occur due to cooling effects and ejection pin-induced defects
Solution Approach 1:
The patent applies preliminary action by designing a frame structure in the moulding tool that proactively compensates for cooling-induced distortion before the mirror glass is ejected. The frame structure is positioned to provide support during the critical cooling phase, preventing distortion from occurring in the first place rather than attempting to correct it afterward.
Solution Approach 2:
The patent utilizes parameter changes by optimizing the thickness and radius of the frame structure based on the specific geometry of the mirror glass. By adjusting these parameters, the cooling rate and thermal stress distribution are controlled, minimizing distortion while maintaining the weight and safety advantages of plastic glass.
2Strength
If hard coating layers are applied to plastic glass mirrors, then durability is improved, but optical interference occurs affecting image quality
Solution Approach 1:
The patent applies local quality by varying the thickness of the hard coating layer in different regions of the mirror surface. The coating is applied more thinly in areas where optical clarity is critical while maintaining sufficient thickness in less critical areas for protection, thus balancing durability and optical performance locally across the mirror surface.
3Adaptability or versatility
If conventional heating circuits are deposited on mirror glass, then heating function is achieved, but additional manufacturing steps and complexity are required
Solution Approach 1:
The patent merges the heating circuit deposition with the existing metallization process for the mirror glass. By integrating the heating circuit into the same sputtering or vapor deposition step used for creating the reflective coating, the heating function is achieved without adding separate manufacturing steps, thereby reducing overall process complexity.
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 reduces distortion and vibration in the mirror, enhances optical clarity by minimizing interference, and ensures reliable heating without hotspots, resulting in a more accurate and durable automotive rearview mirror.
Implementation Method 1
a heating layer (52) of heat conducting alloy, for example nickel- and titanium-based, which is resistively heated
Implementation Method 2
In the first process station 43 the support drum with the mirror substrates is loaded. In the following stations plasma for a plasma vapour deposition process 44 is activated and the layers are applied.
Data Source
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AI summary
The invention related to a rear view mirror (1) using a plastic glass material to combine several functions as fixing and heating.