Multilayer Optical Film with Absorptive Layers for Color Stability
Solution Overview
Problem
Conventional infrared reflecting optical films exhibit undesirable color shift with incident angle due to the infrared reflection band shifting into or within the visible range, affecting the reflection and transmission of light.
Innovation Solution
Incorporating optically absorptive materials in the multilayer optical film, specifically in the outer layers and alternating layers, to reduce color shift by suppressing harmonics of the infrared reflection band, thereby maintaining consistent reflectance and transmittance across varying angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional infrared reflecting optical films are used to achieve high infrared reflectance, then solar heat gain is reduced, but color shift with incident angle occurs due to infrared reflection band shifting into the visible range
Solution Approach 1:
The patent applies this principle by converting the harmful effect of infrared reflection band harmonics (which cause color shift) into a beneficial effect. By strategically placing optically absorptive material in specific layers, the absorptive material absorbs the harmonic frequencies that would otherwise cause color shift, while allowing the primary infrared reflection function to remain intact. This transforms the problematic harmonic frequencies into absorbed energy, eliminating color shift without sacrificing infrared reflectance.
Solution Approach 2:
The patent applies this principle by making different parts of the optical film have different functions. Specifically, certain layers contain optically absorptive material while others do not, creating a localized functional differentiation. The layers with absorptive material specifically target and absorb harmonic frequencies, while layers without absorptive material maintain the primary infrared reflection function. This local quality differentiation allows the film to simultaneously achieve high infrared reflectance and minimal color shift.
2Stability of the object's composition
If optically absorptive material is added to suppress harmonics and reduce color shift, then color consistency improves, but visible light transmittance may be affected
Solution Approach 1:
The patent applies this principle by segmenting the optical film into multiple layers with different functional properties. Not all layers contain optically absorptive material - only specific layers are designed to absorb harmonics. This segmentation allows the film to selectively absorb only the harmful harmonic frequencies while maintaining high visible light transmittance in the other layers. The functional differentiation between layers enables simultaneous achievement of color consistency and high visible light transmission.
3Stability of the object's composition
If multiple alternating layers are used to achieve precise optical control, then infrared reflectance and color stability improve, but device complexity increases
Solution Approach 1:
The patent applies this principle by designing the alternating layer structure where each layer type serves multiple functions. The layers with optically absorptive material not only absorb harmonics to reduce color shift but also contribute to the overall optical interference pattern that achieves high infrared reflectance. The layers without absorptive material provide the necessary optical path difference and interference effects. This multi-functionality of the layer structure reduces the need for additional specialized components, thereby managing complexity while achieving superior optical performance.
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 minimizes color shift in reflected and transmitted light across different incident angles, achieving high infrared reflectance and low visible light transmittance while maintaining neutral or predetermined colorimetric parameters, suitable for applications like window films and laminated windshields.
Implementation Method 1
optically absorptive material dispersed in at least one layer of the multilayer optical film
Implementation Method 2
average optical reflectance in an infrared wavelength range extending from about 850 nm to about 1200 nm of greater than about 60%
Data Source
AI summary
A multilayer optical film includes a plurality of alternating polymeric first and second layers and optically absorptive material dispersed in at least one layer of the multilayer optical film. The multilayer optical film has an average optical transmittance in a visible wavelength range extending from about 450 nm to about 650 nm of about 0.5% to about 40%, an average optical reflectance in the visible wavelength range of less than about 40%, and an average optical reflectance in an infrared wavelength range extending from about 850 nm to about 1200 nm of greater than about 60%. For illuminant D65 light incident on the multilayer optical film, the multilayer optical film reflects and transmits portions of the incident light as reflected and transmitted lights that have color shifts below specified limits in a CIE L*a*b* color space. A glass laminate includes the multilayer optical film disposed between glass layers.