Segmented Light Coupling for Vehicle Panes Under Thermal Stress

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Solution Overview

Problem

Existing vehicle panes with lighting devices experience adhesive bond detachment due to high stresses from temperature changes and differing thermal expansion coefficients between glass and plastics materials in the light coupling-in elements.

Innovation Solution

The lighting device incorporates multiple LEDs with individual light coupling-in elements, each with its own attachment mechanism, such as adhesive bonding, potting material, or holding devices, to reduce thermal expansion stresses and improve curvature adaptation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a single long light coupling-in element is used, then the lighting device structure is simple, but high stresses occur in the adhesive bond causing detachment due to temperature changes and different coefficients of thermal expansion

Engineering Contradiction:

Improvelighting device structureVSAvoidadhesive bond stability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The single long light coupling-in element is divided into multiple individual light coupling-in elements arranged side by side. Each element has its own adhesive bond to the light guide layer, which reduces the stress on each individual bond. The segments can expand and contract independently during temperature changes, preventing the adhesive bonds from detaching while maintaining the overall lighting function.

Inventive Principle:

Principle #1Segmentation

2Ease of manufacture

If a single long light coupling-in element is used, then manufacturing is simpler, but the adhesive bond detaches under thermal stress

Engineering Contradiction:

Improvelight coupling-in element productionVSAvoidadhesive bond strength

Core Design Contradiction:

Ease of manufactureVSStrength

Solution Approach 1:

Instead of manufacturing one long light coupling-in element, multiple shorter individual elements are produced and assembled. This segmentation reduces the length of each element, thereby reducing the total adhesive bond area and the stress concentration on each bond. The shorter elements are easier to manufacture with consistent quality, and their individual adhesive bonds maintain stronger attachment under thermal expansion and contraction cycles.

Inventive Principle:

Principle #1Segmentation

3Shape

If a strip-type light coupling-in element is used, then light guidance is achieved, but adaptation to curvature of the vehicle pane is poor

Engineering Contradiction:

Improvelight guidance functionVSAvoidcurvature adaptation

Core Design Contradiction:

ShapeVSAdaptability or versatility

Solution Approach 1:

The light coupling-in elements are segmented into multiple individual units that can be independently positioned and oriented. This segmentation allows each element to adapt to the local curvature of the vehicle pane, while collectively providing continuous light guidance along the desired path. The modular arrangement enables flexibility in conforming to curved surfaces while maintaining the light coupling function.

Inventive Principle:

Principle #1Segmentation

4Illumination intensity

If glass light coupling-in elements are used, then optical quality is improved, but flexibility for curvature adaptation is reduced

Engineering Contradiction:

Improveoptical qualityVSAvoidcurvature adaptation flexibility

Core Design Contradiction:

Illumination intensityVSAdaptability or versatility

Solution Approach 1:

Glass light coupling-in elements are divided into multiple small individual units rather than one long continuous element. Each small glass element maintains the high optical quality of glass material while being small enough to accommodate curvature requirements. The segmented glass elements can be arranged in a configuration that follows the curvature of the vehicle pane, combining the optical advantages of glass with the flexibility needed for curved surfaces.

Inventive Principle:

Principle #1Segmentation

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 design minimizes adhesive bond detachment and enhances curvature adaptation by using smaller, individually attached light coupling-in elements, improving light guidance and reducing material usage while maintaining optical quality.

Implementation Method 1

a lighting device (4), which inputs light into the light guide layer (10) by means of a light coupling-in device (12)

Methodology Applied

Scientific EffectOptical coupling: Refraction

Implementation Method 2

The light coupling-in element is attached via an adhesive bond to an inner side of a light guide layer formed by an inner pane of the multi-layer vehicle pane

Methodology Applied

Scientific EffectAdhesive bonding: Adhesive

Implementation Method 3

high stresses can occur in the adhesive bond, which can cause the adhesive bond to become detached in the case of temperature changes and different coefficients of thermal expansion of the glass material of the light guide layer and of the plastics material of the light coupling-in element

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS12503045B2Vehicle pane with a lighting device

Publication Date: 2025.12.23 WEBASTO AG

AI summary

A vehicle pane with a light guiding layer on the inner side of the pane and with a lighting device, which introduces light into the light guiding layer by a light input coupling device. The lighting device has at least two LEDs, and in that each LED is assigned a light input coupling element, via which light from the respective LED is introduced into the light guiding layer.