P-Polarised HUD Projection Arrangement With Stable Multilayer Coating
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Solution Overview
Problem
Existing head-up display (HUD) projection systems using p-polarised radiation suffer from ghost images due to reflections on windshield surfaces, and known electrically conductive coatings for HUDs face issues with reflection properties, stability, and sun protection, leading to high production costs and unsatisfactory performance.
Innovation Solution
A composite pane with a specific electrically conductive coating comprising multiple thin-film layers, optimized for p-polarised radiation, is used to reflect HUD projector radiation without wedge films, ensuring high reflectance, stability, and sun protection, while avoiding ghost images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a single thin silver layer (5-9 nm) is used for HUD reflection, then ghost images are reduced, but the coating becomes unstable and dewetting occurs during heat treatment
Solution Approach 1:
The patent applies a composite coating structure consisting of multiple thin silver layers (first, second, third silver layers) separated by dielectric layers. This composite structure prevents dewetting during heat treatment while maintaining low ghost image formation. The dielectric layers act as spacers that stabilize the thin silver layers, preventing them from aggregating into islands during thermal processing.
Solution Approach 2:
The coating is segmented into multiple discrete silver layers (first, second, third silver layers) rather than using a single thick layer. Each silver layer is kept thin (5-9 nm) to minimize ghost images, and the segmentation allows each layer to be stabilized independently by the dielectric layers, preventing the dewetting problem that occurs in single thin layers.
2Reliability
If multiple silver layers are used to improve stability, then coating reliability increases, but production cost and complexity increase
Solution Approach 1:
The patent uses extremely thin silver layers (5-9 nm) that are flexible and conformal, deposited as thin films on the windshield substrate. These thin films are stabilized by dielectric layers, creating a flexible but stable coating structure that can be applied to curved surfaces while maintaining reliability and preventing dewetting.
3Ease of manufacture
If existing conductive coatings are used for HUD reflection, then production cost is reduced, but sun protection performance is insufficient
Solution Approach 1:
The multi-layer silver coating structure serves multiple functions simultaneously: it provides HUD reflection by maintaining thin silver layers that minimize ghost images, ensures coating stability through dielectric spacers that prevent dewetting, and delivers effective sun protection through the cumulative reflective and absorptive properties of the multiple silver layers. This single coating structure replaces what would otherwise require separate HUD and sun protection coatings.
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 provides a high-intensity, colour-neutral HUD display with reduced ghost images, effective sun protection, and thermal comfort, using a cost-effective production method.
Implementation Method 1
the projector image is reflected on both external surfaces of the windshield
Implementation Method 2
The problem arises that the projector image is reflected on both external surfaces of the windshield. As a result, in addition to the desired primary image, a slightly offset secondary image also appears, the so-called ghost image ('ghost'). The problem is usually mitigated by arranging the surfaces at an angle relative to one another, in particular by using a wedge-like intermediate layer for the lamination of windshields implemented as a composite pane such that the primary image and the ghost image are superimposed on one another.
Implementation Method 3
each has a very thin silver layer which can cause so-called dewetting problems during heat treatment, which can result in island-like accumulation of the silver instead of a homogeneous layer
Implementation Method 4
a second dielectric layer sequence (M2) comprising a second anti-reflection layer (22.2) and a second optically high-refractive-index layer (22b.2)
Data Source
AI summary
A projection arrangement for a head-up display (HUD), includes a composite pane, which includes an outer pane and an inner pane joined to one another via a thermoplastic intermediate layer and has an HUD region; an electrically conductive coating on the surface of the outer pane or the inner pane facing the intermediate layer or within the intermediate layer; and an HUD projector, which is directed at the HUD region; wherein the radiation of the projector is p-polarised, wherein the electrically conductive coating includes a first dielectric layer or layer sequence, a first electrically conductive layer, a second dielectric layer or layer sequence, a second electrically conductive layer, a third dielectric layer or layer sequence, a third electrically conductive layer, a fourth dielectric layer or layer sequence, a fourth electrically conductive layer, and a fifth dielectric layer or layer sequence.