Thin Optical Filter Composition for UV-IR Cutoff Control
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Solution Overview
Problem
Existing optical filters for solid-state imaging sensors face challenges in achieving desired transmittance properties and simplified production processes, particularly with UV-IR-absorbing layers that are too thick or require complex production methods, and the transmittance properties of alternative layers are unknown.
Innovation Solution
An optical filter with a light-absorbing layer having a thickness of 120 μm or less, composed of copper phosphonate and an organic dye, achieving specific transmittance requirements and simplified production through a composition with controlled by-product concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a UV-IR-absorbing layer is used to shield infrared and ultraviolet light, then the spectral sensitivity of the solid-state imaging sensor can approximate human visual sensitivity, but the layer thickness becomes too large (130-220 μm) causing increased device size
Solution Approach 1:
The patent changes the chemical composition parameters of the light-absorbing layer by using specific organic dyes (cyanine, phthalocyanine, squarylium compounds) with optimized molecular structures and absorption characteristics. This allows achieving the same UV-IR shielding performance with a significantly reduced layer thickness of 5-20 μm compared to conventional 130-220 μm layers
Solution Approach 2:
The patent creates a composite light-absorbing layer by combining organic dye compounds with resin materials (polyvinyl butyral, polyacrylic acid, carboxymethyl cellulose). This composite structure provides both the light absorption functionality and mechanical stability, enabling thin-film implementation while maintaining effective spectral filtering
2Length of stationary object
If a light-absorbing layer with thickness of 120 μm or less is used, then the device size is reduced, but achieving the desired transmittance properties becomes difficult
Solution Approach 1:
The patent precisely controls the concentration ratios of organic dye compounds in the light-absorbing layer. By adjusting the types and amounts of cyanine, phthalocyanine, and squarylium compounds, the patent achieves optimal transmittance properties (70-90% in visible region, <10% in near-infrared region) with thin layers of 5-20 μm thickness
Solution Approach 2:
The patent applies different organic dye compounds with specific absorption characteristics to different wavelength regions. The composite dye system provides localized absorption enhancement in the near-infrared region while maintaining high visible light transmittance, enabling precise spectral control in thin-film configuration
3Reliability
If conventional UV-IR-absorbing layers are used, then infrared and ultraviolet shielding is achieved, but the production process becomes complex
Solution Approach 1:
The patent merges multiple functions into a single light-absorbing layer: UV shielding, visible light transmission, and near-infrared blocking are all achieved in one layer rather than requiring separate layers. This consolidation simplifies the production process by reducing the number of coating and curing steps required
Solution Approach 2:
The composite organic dye system provides multi-functional performance in a single material system. The same light-absorbing layer simultaneously achieves UV cutoff, visible light transmission, and near-infrared blocking, making the filter applicable to various imaging applications without requiring multiple specialized layers
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 optical filter achieves high visible light transmittance, effective near-infrared shielding, and simplified production, conforming to human visual sensitivity with improved light absorption performance.
Implementation Method 1
optical filters including a light-absorbing layer including a light absorber have been attracting attention. The transmittance properties of optical filters including a light-absorbing layer are unlikely to be dependent on the incident angle
Implementation Method 2
an optical filter shielding against infrared light or ultraviolet light is disposed ahead of a solid-state imaging sensor. It has been common for such an optical filter to shield against infrared or ultraviolet light by means of light reflection by a dielectric multilayer film
Data Source
AI summary
An optical filter (1a) has a thickness of 120 μm or less and satisfies the following requirements (i), (ii), (iii), and (iv): (i) an average transmittance in a wavelength range of 450 nm to 600 nm is 74% or more; (ii) a maximum transmittance in a wavelength range of 750 nm to 1080 nm is 1% or less; (iii) an infrared cut-off wavelength being a wavelength which lies in a wavelength range of 550 nm to 700 nm and at which a spectral transmittance is 50% is in a range of 600 nm to 680 nm; and (iv) an ultraviolet cut-off wavelength being a wavelength which lies in a wavelength range of 350 nm to 500 nm and at which a spectral transmittance is 50% is in a range of 350 nm to 420 nm.