Chamfered Cover Glass Roughness Control for Red Reflection Suppression
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Solution Overview
Problem
Existing glass articles in in-vehicle display devices with chamfered end portions prone to red discoloration due to specularly reflected light, which can be mistaken for a failure, and adjusting the antireflection layer configuration to prevent this often narrows its design width.
Innovation Solution
A glass article with specific surface roughness and chamfered portions, where the angle between the chamfered portion and the main surface is controlled to manage surface roughness, ensuring aesthetics and preventing red discoloration by scattering incident light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If the end portion is chamfered with a curved surface to improve impact resistance and design properties, then the aesthetic appearance and impact resistance are improved, but red discoloration occurs due to specularly reflected light
Solution Approach 1:
The invention applies different surface roughness characteristics to different regions of the chamfered portion. Specifically, the first region (closer to the main surface) has a smaller arithmetic mean roughness (Ra1 ≤ 0.20 μm) while the second region (closer to the end surface) has a larger arithmetic mean roughness (Ra2 > 0.20 μm). This local differentiation allows each region to perform its specific function: the first region maintains aesthetics by reducing specular reflection, while the second region prevents red discoloration by scattering light.
Solution Approach 2:
The invention changes the physical parameter of surface roughness (arithmetic mean roughness Ra) to control light reflection behavior. By precisely controlling the Ra values in different regions (Ra1 ≤ 0.20 μm in the first region, Ra2 > 0.20 μm in the second region), the invention transforms the optical properties of the chamfered surface to eliminate red discoloration while maintaining aesthetic appearance.
2Object-affected harmful factors
If the configuration of the antireflection layer is adjusted to prevent red discoloration, then red discoloration is avoided, but the design width of the antireflection layer is narrowed
Solution Approach 1:
The invention extracts the red discoloration prevention function from the antireflection layer and assigns it to the surface roughness control of the chamfered portion. By forming a specific roughness profile (Ra1 ≤ 0.20 μm and Ra2 > 0.20 μm) on the chamfered surface, the invention separates the functions: the antireflection layer focuses on reducing overall reflection for aesthetic purposes, while the surface roughness profile specifically handles red discoloration prevention, thereby expanding the design freedom of the antireflection layer.
Solution Approach 2:
The invention introduces surface roughness as an intermediary element between the chamfered structure and the light reflection problem. By controlling the arithmetic mean roughness in different regions, this intermediary mechanism mediates the interaction between light and the chamfered surface, preventing red discoloration without requiring changes to the antireflection layer configuration.
3Object-affected harmful factors
If the surface roughness in the chamfered portion is increased to scatter light and prevent red discoloration, then red discoloration is prevented, but the aesthetic appearance may be degraded
Solution Approach 1:
The invention applies different surface roughness characteristics to different regions of the chamfered portion. Specifically, the first region (closer to the main surface) has a smaller arithmetic mean roughness (Ra1 ≤ 0.20 μm) while the second region (closer to the end surface) has a larger arithmetic mean roughness (Ra2 > 0.20 μm). This local differentiation allows each region to perform its specific function: the first region maintains aesthetics by reducing specular reflection, while the second region prevents red discoloration by scattering light.
Solution Approach 2:
The invention addresses the contradiction by introducing a spatial dimension to the solution - dividing the chamfered portion into multiple regions along the surface and applying different roughness characteristics to each region. This dimensional approach allows simultaneous optimization of both aesthetics (in the region closer to the main surface) and red discoloration prevention (in the region closer to the end surface).
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
Prevents red discoloration of the end portion while maintaining aesthetics and impact resistance, allowing the glass article to be used as a cover material in in-vehicle display devices.
Implementation Method 1
a first chamfered portion having a curved surface shape connecting the side surface portion and the first main surface... in a region where an angle formed between the first chamfered portion and the first main surface is greater than 0° and 40° or less, an average value Ra1 of an arithmetic mean roughness Ra on a surface of the glass article is 0.20 μm or less
Data Source
Figure 1~2
Figure 3~4
Figure 5(A)~5(B)
AI summary
A glass article according to the present invention has a first main surface, a second main surface, and an end face connecting the first main surface and the second main surface. The end face includes a side surface section, and a curved first chamfered part connecting the side surface section and the first main surface. An antireflection layer is provided on the first main surface and the first chamfered part. The average value Ra1 of the arithmetic mean roughness of the surface of the glass article is 0.20 µm or less in a region where the angle formed between the first chamfered part and the first main surface is greater than 0° and at most 40°. The average value Ra3 of the arithmetic mean roughness of the surface of the glass article is 0.30 µm or more on the side surface section and in a region where the angle formed between the first chamfered part and the first main surface is greater than 80°. The average value Ra2 of the arithmetic mean roughness of the surface of the glass article in a region where the angle formed between the first chamfered part and the first main surface is 60° to 80° satisfies expression (1): 0.2 ≤ (Ra2 - Ra1) / (Ra3 - Ra1) ≤ 0.8.