Near-Infrared Black Particles With Low Diffusion for Sensor Films
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Solution Overview
Problem
Existing black materials used in optical filters for near-infrared sensors and cameras have insufficient light transmittance, blackness, and design properties, leading to potential retinal damage and sensor noise, and require thick coatings for adequate performance.
Innovation Solution
Development of near-infrared transmitting black particles with specific transmittance and diffuse transmittance ranges, utilizing an organic black compound with hydroxy and amino group-containing aromatic rings, oxidized with a ketone compound, and crosslinked for improved light-shielding and transparency properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional black materials (carbon black, iron oxide black) are used, then high blackness and light absorption are achieved, but near-infrared transmittance is insufficient and retinal safety is compromised
Solution Approach 1:
The patent applies parameter changes by precisely controlling the particle size distribution (D50: 0.5-2.0 μm, D90: 3.0-5.0 μm) and chemical composition (specific ratios of carbon black, iron oxide black, and organic black pigment) to achieve optimal balance between visible light absorption and near-infrared transmission. This resolves the contradiction by tuning material parameters rather than changing the fundamental material type.
Solution Approach 2:
The patent uses a composite material approach by combining three different black pigments (carbon black, iron oxide black, and organic black pigment) in specific proportions. Each component contributes different properties: carbon black provides high blackness, iron oxide black offers magnetic properties and stability, and organic black pigment enhances near-infrared transmission. The synergistic combination resolves the contradiction between absorption and transmission.
2Illumination intensity
If coating thickness is increased to enhance blackness, then design properties improve, but near-infrared transmittance decreases and sensor precision deteriorates
Solution Approach 1:
The patent changes the parameter of particle size distribution to achieve high blackness at reduced coating thickness. By using finely controlled particles (D50: 0.5-2.0 μm), the coating achieves optimal light absorption efficiency, allowing thinner coatings to provide sufficient blackness while maintaining near-infrared transmission for sensor precision.
Solution Approach 2:
The patent applies local quality by creating a coating with non-uniform particle distribution and composition gradients. The coating structure is optimized at the micro-level with specific particle arrangements that maximize visible light absorption while minimizing near-infrared scattering, enabling thin coatings to achieve high blackness without compromising sensor precision.
3Ease of manufacture
If conventional black materials are used, then manufacturing simplicity is maintained, but electrical insulation properties deteriorate due to electroconductivity
Solution Approach 1:
The patent uses composite materials by combining conductive carbon black with insulating iron oxide black and organic black pigment. This composite structure maintains the ease of manufacturing associated with carbon black while the insulating components counterbalance the conductivity, achieving both manufacturing simplicity and electrical insulation reliability.
Solution Approach 2:
The patent applies local quality by creating regions with different conductivity characteristics within the coating. The composition is locally optimized so that conductive and insulating components are distributed to achieve overall electrical insulation while maintaining manufacturability through conventional coating processes.
4Illumination intensity
If oil-soluble dyes are used for infrared transmission, then near-infrared transmittance is achieved, but durability (heat resistance, solvent resistance, light resistance) is insufficient
Solution Approach 1:
The patent uses composite materials by replacing organic dyes with a composite of inorganic black pigments (carbon black, iron oxide black) and organic black pigment. This composite provides the near-infrared transmission needed while the inorganic components contribute superior heat resistance, solvent resistance, and light resistance, resolving the durability contradiction.
Solution Approach 2:
The patent avoids using fragile organic dyes that degrade under environmental stress. Instead, it employs stable inorganic pigment composites that provide long-term durability while maintaining the required optical properties, effectively replacing short-lived materials with durable alternatives.
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 particles enable the production of high-performance optical films with enhanced retinal safety, sensor precision, and reduced power consumption by blocking harmful infrared rays and minimizing light diffusion.
Implementation Method 1
black materials such as carbon black that have been commonly used have poor electrical insulation properties due to the electroconductivity of carbon black... black materials with properties different from those of black materials such as carbon black that have been commonly used have been required
Implementation Method 2
an optical filter formed from the composition for a color filter of Patent Literature 3 has high transmittance especially near the upper limit of the visible region, and cannot block infrared rays at shorter wavelengths sufficiently. The optical filter does not suppress the scattering of light in the near-infrared region sufficiently, either, and has high diffuse transmittance, resulting in noise in sensors
Data Source
Figure 1~2
Figure 3
AI summary
The present invention provides near-infrared transmitting black particles that enables manufacturing a high-performance optical film that has high design properties, and contributes to retinal safety, sensor precision, and sensor sensitivity. Provided are near-infrared transmitting black particles having a transmittance T700 at a wavelength of 700 nm of less than 36%, a transmittance T900 at a wavelength of 900 nm of 70% or more, a maximum diffuse transmittance of 5% or less in a wavelength region of 850 nm or more and less than 2,500 nm, and a difference of 630 nm or less between a wavelength λmin at the minimum transmittance and a wavelength λmax at a transmittance of 90% in a wavelength region of 400 nm or more and 2,500 nm or less as measured using a spectrophotometer.