Embedded Microstructures for Daylight Redirecting Window Films

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Solution Overview

Problem

Existing light directing sheet materials have limited bend angles, typically below 60 degrees, and are prone to soiling and damage, with exposed micro-prismatic surfaces also redirecting normal incidence rays, impeding views.

Innovation Solution

A sheet-form light control material with a layered structure featuring a soft and elastic polymeric core sandwiched between rigid outer sheets, incorporating internal total internal reflection (TIR) surfaces to redirect off-normal light rays at high bend angles without external texturing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If prismatic surface microstructures are used to redirect light, then light redirection is achieved, but the bend angle is limited to below 60 degrees

Engineering Contradiction:

Improvelight redirection capabilityVSAvoidbend angle range

Core Design Contradiction:

Illumination intensityVSAdaptability or versatility

Solution Approach 1:

The patent transitions from surface-level prismatic structures to subsurface embedded microstructures. The light redirecting elements are positioned within the polymeric core rather than on the surface, allowing light to be redirected at high angles (exceeding 90 degrees) while maintaining smooth external surfaces. This dimensional relocation resolves the bend angle limitation of traditional prismatic surfaces.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Illumination intensity

If exposed micro-prismatic surfaces are used for light redirection, then light control is achieved, but the surfaces are prone to soiling and damage

Engineering Contradiction:

Improvelight control capabilityVSAvoidsurface durability

Core Design Contradiction:

Illumination intensityVSReliability

Solution Approach 1:

The light redirecting microstructures are extracted from the external surface and embedded within the polymeric core. This removal of exposed micro-prismatic surfaces eliminates their vulnerability to soiling and physical damage, while the embedded structures continue to perform light redirection functions through the transparent polymeric medium.

Inventive Principle:

Principle #2Taking out (Extraction)

3Illumination intensity

If micro-prismatic surfaces are used to redirect light, then off-normal rays are redirected, but normal incidence rays are also redirected impeding views

Engineering Contradiction:

Improveoff-normal light redirectionVSAvoidview obstruction

Core Design Contradiction:

Illumination intensityVSObject-affected harmful factors

Solution Approach 1:

The embedded microstructures are designed with specific geometric properties that create angular selectivity. The subsurface position and orientation of these structures enable them to interact primarily with off-normal incident light rays, redirecting them at high angles, while allowing normal incidence rays to pass through with minimal interaction, thereby preserving clear views.

Inventive Principle:

Principle #3Local quality

4Reliability

If lamination is applied to protect micro-prismatic surfaces, then surface protection is achieved, but air gaps impair optical performance

Engineering Contradiction:

Improvesurface protectionVSAvoidoptical performance

Core Design Contradiction:

ReliabilityVSIllumination intensity

Solution Approach 1:

The patent eliminates the need for protective lamination by making the microstructures themselves durable through embedding. The robust polymeric core protects the embedded microstructures from environmental factors, removing the requirement for additional protective layers that would create air gaps and compromise optical performance.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

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 enables efficient redirection of off-normal light rays at high deflection angles, maintaining smooth external surfaces and preventing soiling, while allowing normal incidence light to pass through unimpeded, enhancing natural illumination and light control.

Implementation Method 1

The light redirecting functionality is provided by an array of thin reflectors embedded into the body of the core material and configured to reflect at least a portion of light incident onto the sheet surface from an off-normal direction. In at least one embodiment, the reflectors comprise deep and narrow channels formed in a surface of the core material and configured to reflect light by means of a total internal reflection (TIR).

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Data Source

PatentUS12305819B2Method of making daylight redirecting window films employing embedded microstructures

Publication Date: 2025.05.20 S V V TECH INNOVATIONS INC

AI summary

A method of making a daylight redirecting window film having a layered structure with a total thickness of less than one millimeter and having at least two optical films bonded together. One of the optical films has a first light redirecting layer disposed on a first side of the film and including a linear array of light redirecting structures configured to reflect light using a total internal reflection and defining a parallel array of narrow channels, and a second light redirecting layers disposed on an opposite second side of the film and including light scattering surface microstructures. The method includes coating a surface of at least one of the films with an optical adhesive, positioning the optical films such that the top portions of the light redirecting structures face inwards, and bonding the films together to form a monolithic multi-layer light redirecting film structure.