Diffuse Reflective Optical Films with Selective Birefringence Reduction

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Solution Overview

Problem

Existing diffusely reflective optical films require selective pressure and thinning to achieve patterning, which can be impractical and may alter the optical properties of the film.

Innovation Solution

The method involves selectively reducing the birefringence of polymer materials in specific zones of the film using targeted energy delivery, such as light, to create internally patterned zones with different reflective characteristics without altering the film's thickness or morphology, allowing for the creation of various optical effects like diffusely reflective polarizers, mirrors, or window-like appearances.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If selective pressure and thinning are applied to achieve patterning, then the film can be patterned, but the optical properties of the film are altered and the process becomes impractical

Engineering Contradiction:

Improvepatterning precisionVSAvoidoptical property stability

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent applies localized thermal energy to selectively reduce birefringence in specific zones of the film. By controlling temperature parameters in targeted areas, the refractive index anisotropy is modified to create patterned optical effects without physically altering the film structure through pressure or thinning

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention replaces mechanical patterning methods (pressure and thinning) with a thermal-field-based approach. Instead of applying physical force to deform or remove material, localized heating is used to induce optical property changes through birefringence reduction, thereby preserving film integrity

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Adaptability or versatility

If surface coatings are applied to create optical effects, then the desired optical properties are achieved, but the film structure becomes more complex and security applications are limited

Engineering Contradiction:

Improveoptical effect varietyVSAvoidfilm structure complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent creates spatially varying optical properties by selectively modifying birefringence in specific zones of the film. Different regions exhibit different optical characteristics (reflective, transmissive, or polarizing) through localized thermal treatment, eliminating the need for multiple surface coatings while achieving diverse optical effects

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention removes the need for surface coatings by integrating the optical functionality directly into the bulk film structure. Through selective birefringence reduction, the film itself generates the desired optical effects without requiring additional coating layers

Inventive Principle:

Principle #2Taking out (Extraction)

3Manufacturing precision

If dedicated hardware is used for pattern creation, then precise patterns can be produced, but the manufacturing process becomes less flexible and more costly

Engineering Contradiction:

Improvepattern precisionVSAvoidmanufacturing flexibility

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The patent employs a dynamic thermal field that can be rapidly repositioned and reconfigured to create different patterns. Instead of static dedicated hardware for each pattern, a movable heat source allows flexible pattern creation by simply changing the positioning and timing of thermal application

Inventive Principle:

Principle #15Dynamics

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

This approach enables the production of films with distinct optical properties in different zones without surface coatings, enhancing security applications and allowing for flexible pattern creation without dedicated hardware, while maintaining the film's physical integrity and optical properties.

Implementation Method 1

selectively reducing, in a second zone but not in a neighboring first zone, the birefringence of at least one of the polymer materials

Methodology Applied

Scientific EffectBirefringence: Birefringence

Implementation Method 2

The heat source used by Ulsh et al. is said to soften the surface of the optical film rapidly enough to cause softening of the film surface

Methodology Applied

Scientific EffectLight absorption and heating: Absorption (EM radiation)

Data Source

PatentUS9939560B2Diffuse reflective optical films with spatially selective birefringence reduction

Publication Date: 2018.04.10 3M INNOVATIVE PROPERTIES CO

AI summary

A diffusely reflective optical film includes a blended layer extending from a first to a second zone of the film. The blended layer includes first and second polymer materials separated into distinct first and second phases, respectively. The blended layer may have the same composition and thickness in the first and second zones, but different first and second diffusely reflective characteristics in the first and second zones, respectively. The difference between the first and second diffusely reflective characteristics may not be attributable to any difference in composition or thickness of the layer between the first and second zones. Instead, the difference between the first and second diffusely reflective characteristic may be attributable to a difference in birefringence of the first and/or second polymer materials between the first and second zones. The blend morphology of the blended layer may be substantially the same in the first and second zones.