Glass Ceramic Surface Treatment for Low-Scattering Image Covers
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Solution Overview
Problem
Conventional glass ceramic articles used in consumer electronic devices suffer from light scattering due to the migration of alkali species to their surface, forming alkali hydroxides that reduce image fidelity.
Innovation Solution
A method involving ion-exchange and post-IOX polishing processes, using salt baths with specific compositions and temperatures, to remove a controlled depth of material from the glass ceramic surface, followed by a coating process to prevent alkali species migration and scattering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If ion-exchange process is used to strengthen glass ceramic, then surface compressive stress increases, but alkali species migration to surface increases causing light scattering
Solution Approach 1:
The patent applies preliminary action by performing ion-exchange process followed by a controlled removal step (chemical etching or mechanical polishing) to eliminate the problematic surface layer where alkali species accumulate. This preliminary treatment prevents light scattering before it occurs during product use, while maintaining the compressive stress benefit in the bulk material.
Solution Approach 2:
The patent extracts the harmful surface layer containing migrated alkali species through controlled removal processes. By removing a thin surface layer (typically 1-10 micrometers) after ion-exchange, the patent eliminates the source of light scattering while preserving the strengthened bulk material with beneficial compressive stress.
2Ease of manufacture
If conventional glass ceramic is used, then manufacturing is simple, but light scattering features form on surface reducing image fidelity
Solution Approach 1:
The patent applies preliminary action by incorporating a surface treatment step (chemical etching or mechanical polishing) after ion-exchange but before final assembly. This preliminary surface refinement ensures high optical quality is achieved during manufacturing, preventing light scattering issues that would otherwise require complex post-processing or lead to product rejection.
3Strength
If ion-exchange process is performed, then surface compressive stress is enhanced, but surface blemishes form due to alkali hydroxide separation
Solution Approach 1:
The patent extracts the problematic surface layer containing separated alkali hydroxides and surface blemishes through controlled removal processes. By removing this compromised surface layer after ion-exchange, the patent eliminates reliability issues while preserving the enhanced compressive stress in the underlying bulk material.
Solution Approach 2:
The patent applies preliminary action by performing surface removal treatments to eliminate blemish-prone layers before final product assembly. This preliminary correction of surface integrity issues ensures reliable performance during product lifecycle, preventing premature failure from surface defects.
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 method effectively reduces light scattering by minimizing alkali species migration, maintaining image fidelity and surface integrity under varying environmental conditions.
Implementation Method 1
contacting at least a portion of the glass ceramic article with a first salt bath to form an ion-exchanged glass ceramic article
Implementation Method 2
removing a portion of the ion-exchanged glass ceramic article to a depth greater than or equal to 1 μm and less than or equal to 10 μm from a first major surface
Data Source
AI summary
Disclosed herein are methods of treating glass ceramic articles including contacting at least a portion of a glass ceramic article with a first salt bath to form an ion-exchanged glass ceramic article and removing a portion of the ion-exchanged glass ceramic article to a depth greater than or equal to 2 μm and less than or equal to 10 μm from a first major surface of the ion-exchanged glass ceramic article to form a post-IOX polished glass ceramic article. The first salt bath includes greater than or equal to 20 wt. % and less than or equal to 90 wt. % KNO3, greater than or equal to 10 wt. % and less than or equal to 80 wt. % NaNO3, greater than or equal to 0.03 wt. % and less than or equal to 0.3 wt. % LiNO3, and greater than or equal to 0.2 wt. % and less than or equal to 1 wt. % silicic acid.