Retroreflective Sheet Void Collapse Prevention

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Solution Overview

Problem

Retroreflective sheeting experiences degradation in retroreflectivity when subjected to pressure in the thickness direction, such as when bent or embossed, due to the collapse of voids between retroreflective elements and cavities, leading to reduced reflectivity.

Innovation Solution

Incorporating particles between the retroreflective elements and the back face layer, which are fixed in place to support the voids and prevent their collapse, utilizing a refractive index difference to maintain light reflection, with optimal particle size and distribution to enhance retroreflectivity and adhesive strength.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If voids are formed between retroreflective elements and cavities to improve retroreflectivity, then light reflection is enhanced, but the voids collapse when pressure is applied in the thickness direction, causing retroreflectivity degradation

Engineering Contradiction:

ImproveretroreflectivityVSAvoidvoid structure stability

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

Particles are introduced as intermediary elements between the retroreflective elements and the back face layer. These particles serve as structural support for the voids, preventing their collapse when pressure is applied, while still allowing the voids to maintain their light-reflecting function. The particles act as a mediator that preserves both the retroreflectivity and the structural stability.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The retroreflective sheeting employs a composite structure combining retroreflective elements, particles, and a back face layer. This composite design integrates multiple functional components: the retroreflective elements provide light reflection, the particles provide structural support to prevent void collapse, and the back face layer provides attachment. The composite structure resolves the contradiction by distributing functions across different materials.

Inventive Principle:

Principle #40Composite materials

2Illumination intensity

If no metal deposited film is used to improve lightness, then printed parts prominence is enhanced, but the retroreflective sheeting becomes more susceptible to void collapse under pressure

Engineering Contradiction:

ImprovelightnessVSAvoidretroreflectivity under pressure

Core Design Contradiction:

Illumination intensityVSReliability

Solution Approach 1:

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The particles are strategically positioned in specific locations within the retroreflective sheeting structure, particularly at critical points where void support is needed. This local placement of particles provides targeted reinforcement without compromising the overall lightness or requiring metal films, addressing both the lightness requirement and the pressure resistance need.

Inventive Principle:

Principle #3Local quality

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 suppresses the degradation of retroreflectivity under pressure, improving the sheeting's performance on curved or embossed surfaces while maintaining high lightness and chroma, as demonstrated by controlled void formation and increased adhesive strength.

Implementation Method 1

With the refractive index difference between the low refractive index gas and the retroreflective element, light that has been entered from the optically transparent layer side and has reached the interface between the retroreflective elements and the voids can be reflected to the optically transparent layer side

Methodology Applied

Scientific EffectRefraction: Refraction

Implementation Method 2

retroreflective sheetings have the properties that can reflect incident light to the light source side

Methodology Applied

Scientific EffectReflection: Reflection

Data Source

PatentEP3451030B1Retroreflective sheet

Publication Date: 2020.12.09 NIPPON CARBIDE KOGYO KK

Figure 1~3
Figure 4

AI summary

A retroreflective sheeting includes a retroreflective layer 20 having a plurality of retroreflective elements 24 on a first face; a back face layer 40 provided opposite to a face of the retroreflective layer 20 on a side of the retroreflective element 24, the back face layer 40 having an attachment portion 42 attached to the retroreflective elements 24; a plurality of particles 30 arranged between the retroreflective elements 24 and the back face layer 40; and a void 32 formed between the retroreflective elements 24 and the plurality of particles 30.