Acrylic Resin Sensor Covers for Angle-Stable Near-Infrared Transmission
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Solution Overview
Problem
Existing optical sensor protection covers made from polycarbonate resin lack scratch resistance and heat resistance, and acrylic resin covers do not maintain consistent transmission properties across varying incident angles due to downsizing of optical sensor devices.
Innovation Solution
An acrylic resin composition comprising an acrylic resin and a light absorber, with specific optical properties and a deflection temperature under load of 110°C or more, ensuring high scratch resistance and consistent near-infrared transmission across different angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a bandpass filter with multilayer thin film is used to block visible light and transmit near-infrared rays, then the optical filtering function is achieved, but the transmittance varies greatly depending on the angle of incidence
Solution Approach 1:
The patent changes the material parameter from multilayer thin film to resin material with specific optical absorption characteristics. The resin is formulated to have wavelength-selective absorption that is independent of incident angle, fundamentally changing how optical filtering is achieved from structural interference to material absorption.
Solution Approach 2:
The patent uses a composite resin material containing specific additives (such as carbon black or metal oxide particles) dispersed in a transparent resin matrix. This composite structure provides both the optical filtering function and angle-independent transmittance characteristics that neither component alone could achieve.
2Strength
If polycarbonate resin is used for sensor protection cover, then scratch resistance is improved, but surface hardness is insufficient
Solution Approach 1:
The patent creates a composite resin material by dispersing hard particles (such as alumina, silica, or titania) in a transparent resin matrix. This composite structure provides both scratch resistance from the hard particles and maintains the molding advantages of thermoplastic resin, while also enabling optical filtering functionality.
Solution Approach 2:
The patent applies surface hardening treatment or coating to the sensor protection cover, creating a layer with different properties than the bulk material. The surface layer provides enhanced hardness and scratch resistance, while the bulk material maintains its toughness and optical properties.
3Temperature
If acrylic resin is used for sensor protection cover, then heat resistance is improved, but dimensional stability at high temperatures is insufficient
Solution Approach 1:
The patent modifies the acrylic resin composition by adding crosslinking agents or using copolymers with restricted rotation groups. These compositional changes increase the glass transition temperature and reduce thermal expansion, thereby improving dimensional stability at high temperatures while maintaining heat resistance.
4Volume of moving object
If device size is reduced, then miniaturization is achieved, but the proportion of oblique incident light increases
Solution Approach 1:
The patent changes the optical mechanism from angle-dependent interference (multilayer film) to angle-independent material absorption (resin with wavelength-selective absorbers). This parameter change in the optical filtering mechanism eliminates the harmful effect of oblique incident light that arises from device miniaturization.
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 composition provides excellent visible light blocking and near-infrared transmission with minimal angle dependence, along with high scratch resistance and dimensional stability.
Implementation Method 1
an acrylic resin composition containing an acrylic resin and a light absorber
Implementation Method 2
transmitting near-infrared rays of a specific wavelength
Data Source
AI summary
An acrylic resin composition for sensor protection covers, comprising: an acrylic resin (A); and a light absorber (B), wherein the acrylic resin composition has a deflection temperature under load of 110°C or more, and a 1 mm thick molded article comprising the acrylic resin composition has optical properties that satisfy all of the following conditions (i) to (v): (i) a maximum transmittance of 10% or less when light with a wavelength of 380 nm to 700 nm is incident on the molded article at an incident angle of 0°; (ii) a minimum transmittance of 85% or more when light with a wavelength of 850 nm to 950 nm is incident on the molded article at an incident angle of 0°; (iii) an average transmittance of 85% or more when light with a wavelength of 1500 nm to 1600 nm is incident on the molded article at an incident angle of 0°; (iv) 0.9≤(transmittance when light with a wavelength of 900 nm is incident on the molded article at an incident angle of 60°)/(transmittance when light with a wavelength of 900 nm is incident on the molded article at an incident angle of 0°)≤1.1; and (v) 0.9≤(transmittance when light with a wavelength of 1550 nm is incident on the molded article at an incident angle of 60°)/(transmittance when light with a wavelength of 1550 nm is incident on the molded article at an incident angle of 0°)≤1.1.