Near Infrared Cut Filter Glass Oxidant Process
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Solution Overview
Problem
Conventional near infrared cut filters for digital cameras, especially those with a thickness of 0.15 mm, face issues with color tone deviation due to high CuO concentrations affecting visible light transmittance and chemical durability, leading to reduced spectral transmittance in the visible region.
Innovation Solution
A near infrared cut filter glass is produced with a specific composition including P2O5, AlF3, MgF2, CaF2, SrF2, BaF2, ZnF2, LiF, NaF, KF, CuO, and Sb2O3, with an oxidant, to control Cu+ ion concentration and maintain high transmittance in the visible region, using a process that oxidizes Sb3+ ions to Sb5+ ions to stabilize Cu2+ ions, ensuring effective near infrared cutting characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the concentration of CuO is increased to achieve sufficient near infrared cutting characteristics with a thin filter thickness of about 0.15 mm, then the near infrared cutting performance is improved, but the concentration of Cu+ ions increases which causes the spectral transmittance in the visible region of from 400 to 500 nm to decrease and the glass to turn green, thereby deteriorating the transmitting characteristic in the visible region
Solution Approach 1:
The patent changes the oxidation state parameter of copper ions by adding an oxidant (nitrate compound, sulfate compound, peroxide, perchlorate, or chloric acid) to the glass composition. This transforms Cu+ ions (which absorb visible light and cause green coloration) into Cu2+ ions (which provide near infrared cutting without visible light absorption). The oxidant creates an oxidizing atmosphere during melting that stabilizes copper in the +2 oxidation state, thereby resolving the contradiction between achieving sufficient near infrared cutting with thin filter thickness and maintaining high visible light transmittance.
2Reliability
If a phosphate glass containing CuO is used to cut near infrared light, then the near infrared cutting characteristics are achieved, but the chemical durability is insufficient and weathering is formed on the glass surface, making it difficult to use for long time
Solution Approach 1:
The patent creates a composite glass system by combining phosphate glass (P2O5) with fluorophosphate components (metal fluorides such as AlF3, MgF2, CaF2, SrF2, BaF2, ZnF2, LiF, NaF, or KF) and CuO. This composite structure leverages the near infrared cutting capability of phosphate glass while the fluorophosphate components significantly improve chemical durability and weather resistance. The synergistic combination allows the glass to maintain both functional performance and long-term stability.
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 glass achieves high transmittance in the visible region of 400 to 600 nm with a high CuO concentration, maintaining chemical durability and preventing color tone deviation, making it suitable for thin filters without compromising near infrared cutting efficiency.
Implementation Method 1
a large number of Cu2+ ions coordinated with oxygen ions are formed in an oxidating melting atmosphere, to show a blue green color, whereby the glass shows a near infrared cutting characteristics
Implementation Method 2
it is necessary for the glass to contain a high concentration of CuO. However, when the content of CuO in the above fluorophosphates glass increases, the concentration of Cu+ ions having an absorption wavelength in the vicinity of from 300 to 600 nm in the glass increases
Implementation Method 3
a phosphate glass containing CuO as an additive for selectively absorbing near infrared wavelength
Data Source
AI summary
The present invention provides a process for producing a near infrared cut filter glass by melting and forming a glass material blended; and from 0.1 to 5% as represented by mass percentage of an oxidant of at least of a nitrate compound, a sulfate compound, a peroxide, a perchlorate and chloric acid as well as a near infrared cut filter glass.