Bent Glass Plate Head-Up Display Surface Roughness
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Solution Overview
Problem
Conventional head-up display devices using bent glass plates with arithmetic mean roughness of 5 nm or smaller face issues with adhesive layer stability and visibility due to high smoothness, leading to potential detachment and reduced image clarity.
Innovation Solution
A glass plate with a bent portion, where the arithmetic mean roughness of the first main surface is 5 nm or smaller and the second main surface is larger than 5 nm, ensuring sufficient adhesive performance and reduced external light scattering, thereby enhancing image resolution and visibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the arithmetic mean roughness of the second main surface is made 5 nm or smaller to achieve high image resolution, then the resolution of the virtual image is improved, but the adhesive layer cannot be stably held during long-term use
Solution Approach 1:
The patent applies different surface roughness characteristics to different surfaces of the glass plate: the first main surface (image-forming surface) maintains arithmetic mean roughness Ra1 of 5 nm or smaller for high image resolution, while the second main surface (adhesive attachment surface) has arithmetic mean roughness Ra2 larger than 5 nm for stable adhesive holding. This local differentiation resolves the contradiction between image quality and adhesive stability.
2Manufacturing precision
If the arithmetic mean roughness of the second main surface is made 5 nm or smaller to achieve high image resolution, then the resolution of the virtual image is improved, but external light enters directly without scattering, lowering visibility
Solution Approach 1:
The patent differentiates surface functions by assigning different roughness characteristics to different surfaces: the first main surface maintains Ra1 ≤ 5 nm for high-resolution image formation, while the second main surface has Ra2 > 5 nm to scatter external light and improve visibility. This local quality differentiation simultaneously achieves both high resolution and good visibility.
3Shape
If the arithmetic mean roughness of the second main surface is made 5 nm or smaller, then the smoothness is high for better image quality, but adhesive performance becomes insufficient
Solution Approach 1:
The patent optimizes each surface for its specific function: the first main surface maintains Ra1 ≤ 5 nm for high smoothness and image quality, while the second main surface has Ra2 > 5 nm to provide sufficient adhesive performance. This local quality optimization resolves the contradiction between surface smoothness and adhesive strength.
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 improves adhesive stability and image resolution by maintaining high smoothness on the first main surface while increasing roughness on the second main surface, reducing the likelihood of detachment and external light interference, thus providing improved performance in head-up display devices.
Implementation Method 1
image forming light L1 emitted from a projector 91A is reflected by a path-folding mirror 92A and a reflection mirror 93A to be projected onto a windshield WS
Implementation Method 2
external light that enters on the second main surface 922B from outside the glass plate goes toward the user D side immediately, possibly lowering the visibility of the virtual image V2
Data Source
Figure 1(A)~1(B)
Figure 2(A)~2(B)
Figure 3(A)~3(B)
AI summary
This glass plate for moving bodies has a bent part and is provided on a moving body. This glass plate for moving bodies is characterized in that: the arithmetic mean roughness Ra1 (nm) of a first main surface and the arithmetic mean roughness Ra2 (nm) of a second main surface satisfy formula (1); the Ra1 is 5 nm or less; and the Ra2 is more than 5 nm. Ra2 - Ra1 > 0.5 nm (1)