Asymmetric Reflective Film Glass Laminate for Head-Up Display Ghost Control
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Solution Overview
Problem
Ghost images reflected from the outer surfaces of glass laminates in head-up displays degrade the image quality, and traditional wedge designs for shifting ghost images are costly and difficult to implement effectively.
Innovation Solution
A reflective film is asymmetrically disposed between glass layers with a thinner adhesive layer facing the projector and a thicker adhesive layer facing away, shifting ghost images closer to the primary reflection and using a thinner optically clear adhesive (OCA) instead of traditional PVB for improved impact resistance and reduced waviness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a reflective film is used in glass laminate for head-up display, then image reflection is achieved, but ghost images are generated that degrade image quality
Solution Approach 1:
The patent applies asymmetry by making the adhesive layers on either side of the reflective film have different thicknesses. The first adhesive layer has thickness t1 and the second adhesive layer has thickness t2, where t1 ≠ t2. This asymmetric configuration causes ghost images reflected from the outer glass surfaces to be spatially separated and shifted relative to the primary reflected image, preventing them from overlapping and degrading image quality.
2Strength
If traditional PVB adhesive is used to bond glass layers, then bonding strength is achieved, but waviness occurs in the glass laminate
Solution Approach 1:
The patent changes the material parameter from traditional PVB adhesive to OCA (optically clear adhesive). This material substitution maintains the necessary bonding strength while eliminating the waviness problem, as OCA provides a more stable and flat bonding interface between the glass layers and reflective film.
3Reliability
If thicker adhesive layers are used to bond reflective film, then bonding reliability is improved, but ghost image separation increases degrading image sharpness
Solution Approach 1:
The patent optimizes the thickness parameters of the adhesive layers by using asymmetric thicknesses (t1 and t2) within specific ranges. This parameter optimization ensures sufficient bonding reliability while controlling the ghost image separation distance to maintain image sharpness, achieving a balance between bonding strength and optical performance.
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 enhances image sharpness by overlapping ghost images with the primary reflection, maintains impact resistance, and reduces waviness, providing improved image fidelity and manufacturing efficiency.
Implementation Method 1
the projection light source is used for generating p-polarized light which is incident on a surface of the internal glass panel distal to the intermediate film, the light having an angle of incidence of 42 to 72 degrees, such that the transparent nanofilm can reflect part of the incident p-polarized light
Implementation Method 2
a first adhesive layer disposed between and bonding together the first glass layer and the reflective film, and a second adhesive layer disposed between and bonding together the second glass layer and the reflective film
Data Source
Figure 1A~1B
Figure 2~3B
Figure 3C
AI summary
A glass laminate (100) including first and second glass layers (102,104), a reflective film (110) having opposed first and second major surfaces and disposed between the first and second glass layers (102,104) with the first and second major surfaces facing the respective first and second glass layers (102,104), a first adhesive layer (117) disposed between and bonding together the first glass layer (102) and the reflective film (110), and a second adhesive layer (119) disposed between and bonding together the second glass layer (104) and the reflective film (110) is described. The second adhesive layer (119) is thicker than the first adhesive layer (117) such that the first major surface of the reflective film (110) is separated from an outermost major surface of the first glass layer (102) by a distance d1, the second major surface of the reflective film (110) is separated from an outermost major surface of the second glass layer (104) by a distance d2, and 0.05 < dl/d2 < 0.9.