Glass Substrate Temperature Compensation for In-Plane Stress
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Solution Overview
Problem
Glass substrates used in display devices, such as LCDs, experience distortion when cut into parts due to changes in stress distribution, leading to defective displays, with allowable distortion specifications as low as 2 microns, posing a significant challenge for manufacturers.
Innovation Solution
Identifying and controlling the setting zone temperature range (SZTR) during the glass drawing process, where across-the-ribbon temperature distributions and shapes are critical in minimizing distortion, by determining and adjusting temperature profiles to match specific glass compositions and drawing rates, ensuring each sub-piece exhibits a maximum distortion of 2 microns or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If glass substrates are cut into parts during manufacturing, then production efficiency is improved and multiple panels can be produced simultaneously, but distortion occurs due to stress distribution changes at cut lines
Solution Approach 1:
The patent applies preliminary action by controlling the temperature distribution in the setting zone temperature range (75-150°C above strain point) during the glass drawing process before cutting occurs. By adjusting the across-the-ribbon temperature distribution and across-the-ribbon shape in this critical temperature range, the glass is pre-conditioned to minimize distortion when subsequently cut into sub-pieces. This preliminary thermal conditioning ensures that stress relief during cutting produces minimal shape change, allowing high productivity through simultaneous multi-panel production while maintaining manufacturing precision with distortion specifications of 2 microns or less.
2Manufacturing precision
If across-the-ribbon temperature distribution is controlled in the setting zone temperature range, then distortion is reduced to meet specifications, but process complexity increases
Solution Approach 1:
The patent applies parameter changes by specifically controlling the across-the-ribbon temperature distribution and across-the-ribbon shape parameters within the setting zone temperature range (75-150°C above strain point). By adjusting these thermal parameters during the drawing process, the glass undergoes controlled thermal conditioning that minimizes distortion upon cutting. This parameter control approach achieves distortion specifications of 2 microns or less while managing process complexity through focused control of specific temperature and shape parameters in the critical setting zone, rather than controlling the entire temperature profile.
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 effectively reduces distortion in glass sub-pieces cut from the ribbon, meeting stringent manufacturing specifications and improving the yield of display devices by maintaining low in-plane stress levels, thereby reducing the number of defective panels.
Implementation Method 1
The high rate of cooling causes the glass to take a 'set' at temperatures well above the strain point, e.g., at temperatures approximately 75-150° C. above the strain point for the types of glasses typically used for LCD applications
Implementation Method 2
a temperature distribution in the setting zone temperature range is determined that will result in across-the-ribbon shapes and/or a distribution of across-the-ribbon shapes that will cause sub-pieces cut from glass sheets produced from the ribbon to exhibit a low level of distortion
Data Source
AI summary
Methods of fabricating glass sheets (13) are provided in which the sheets are cut from a glass ribbon (15) composed of a glass having a setting zone temperature range (SZTR). As the glass is drawn, it passes through the SZTR (31) and an across-the-ribbon temperature distribution is produced at least one longitudinal position along the ribbon to compensate for in-plane stress induced in the sheets (13) when flattened. Through such thermal compensation, glass sheets (13) are produced which exhibit controlled levels of distortion when cut into sub-pieces and thus are suitable for use as substrates in the manufacture of, for example, flat panel displays, e.g., LCD displays.