Annular Glass Substrate Separation Using Variable Laser Defect Spacing
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Solution Overview
Problem
Existing methods for manufacturing annular glass substrates for magnetic discs often fail to reliably separate the outer and inner portions of the glass blank, leading to issues like no gap formation or chipping during the separation process.
Innovation Solution
A method involving the formation of a separation line with periodically spaced defects on a glass blank, where the interval between defects varies to create regions with different thermal expansion characteristics, allowing for reliable separation by heating the outer portion at a higher temperature than the inner portion, and optionally forming a second separation line with concentric defects to enhance separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the outer portion of the glass blank is heated at a higher temperature than the inner portion to cause thermal expansion and separation, then the separation process should work, but there are cases where no gap is formed between the outer portion and the inner portion, and thus separation fails
Solution Approach 1:
The patent applies preliminary action by forming defects along a predetermined ring shape on the surface of the glass blank before the separation process. These pre-formed defects serve as initiation points for crack propagation during thermal expansion, ensuring that the separation process reliably produces a gap between the outer and inner portions. The defects are created by laser beam irradiation along a ring shape, positioning them in advance to guide the separation pathway.
Solution Approach 2:
The patent employs parameter changes by controlling the temperature distribution during heating, specifically heating the outer portion at a higher temperature than the inner portion to induce differential thermal expansion. Additionally, the laser beam parameters (wavelength, pulse duration, irradiation pattern) are optimized to create defects with specific characteristics that facilitate reliable crack propagation and separation.
2Reliability
If the outer portion and inner portion are separated by heating, then separation can be achieved, but there are cases where chipping occurs on at least a portion of the edge surfaces
Solution Approach 1:
The patent applies local quality by creating a non-uniform defect distribution along the separation line, with a first region having a first interval between adjacent defects and a second region having a second interval that is shorter than the first interval. This localized variation in defect spacing allows control over crack propagation characteristics, ensuring complete separation while minimizing chipping at critical locations such as edge surfaces.
Solution Approach 2:
The patent converts the potentially harmful effect of thermal stress that could cause chipping into a beneficial controlled crack propagation mechanism. By pre-forming defects at specific intervals, the uncontrolled thermal stress is redirected to propagate cracks along the predetermined defect paths, achieving clean separation without random chipping on edge surfaces.
3Ease of manufacture
If defects are periodically formed with a constant interval along the separation line, then the separation process is simple, but the separation may be unreliable and chipping may occur
Solution Approach 1:
The patent changes the parameter of defect interval along the separation line, transitioning from a constant interval to a variable interval with at least two different values. This parameter variation improves separation reliability by creating more controlled stress distribution and crack propagation paths, while the overall process remains relatively simple and can be implemented using standard laser processing equipment.
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
This method ensures reliable separation of the annular glass substrate from the glass blank with reduced chipping and improved productivity by creating controlled thermal expansion differences and crack formation along the separation lines.
Implementation Method 1
forming, on a glass blank, a separation line that includes a plurality of defects along a predetermined circle by irradiating a surface of the glass blank with a laser beam along the predetermined circle
Implementation Method 2
the outer portion of the glass blank is heated at a higher temperature than the inner portion to cause the outer portion of the glass blank to thermally expand relatively largely compared to the inner portion
Data Source
AI summary
A method for manufacturing an annular glass substrate includes: forming, on a glass blank, a separation line that includes a plurality of defects along a predetermined circle by irradiating a surface of the glass blank with a laser beam along the circle; and separating a portion outside the separation line of the glass blank on which the separation line was formed from a portion inside the separation line by heating the portion outside the separation line at a higher temperature than the portion inside the separation line. The separation line includes: a first region in which the defects are periodically formed and an interval between a pair of adjacent defects is a first interval; and a second region in which an interval between a pair of adjacent defects is shorter than the first interval.