氏名　小野　俊彦
学位の種類　博士（工学）
学位記番号　博甲第219号
学位授与の日付　平成13年3月26日
学位論文題目　Study on LCD Glass Substrate Cutting Using Scribe and Break Method　（液晶ガラスのスクライブ・ブレーク法による切断に関する研究）
論文審査委員
　主査　教授　田中　紘一
　副査　教授　松下　和正
　副査　教授　武藤　睦治
　副査　助教授　許　金泉
　副査　新潟三洋電子株式会社　顧問　谷井　靖夫

• 論文目次
• 論文要旨

［平成12（2000）年度博士論文題名一覧］ ［博士論文題名一覧］に戻る．

Chapter1 Introduction
1. Glass for LCD　p.1
2. Glass cutting process in LCD manufacturing　p.4
3. Scope of this study　p.5
4. References　p.6

Chapter2 Survey and discussion for previous researches on crack creation and propagation
1. Introduction　p.7
2. Background of studies for cracking in glass　p.7
3. Fracture mechanics of cracking by point indentation　p.10
4. Investigation of cracking by point indentation　p.13
5. Investigation of crack creation by scribing　p.17
6. Scribe and break method in LCD manufacturing　p.19
7. Summary　p.21
8. References　p.22

Chapter3 Effects of the scribing wheel features and scribing condition on glass sheet cutting by scribe/break method
1. Introduction　p.25
2. Experiments-I　p.26
2-1. Selection of scribing method in this study.　p.26
2-2. Observation results and discussions on faulty cut surface of LCD glass sheet.　p.26
2-2-1. Faulty cut surface without median crack.　p.27
2-2-2. Faulty cut surface with median crack.　p.28
2-2-3. Rough cut edge having a median crack surface with repetitive pattern.　p.30
2-2-4. Chipping created at scribed line.　p.31
3. Experiments-II　p.31
3-1. Results and Discussions for the effects of scribing load on faulty cut surface.　p.31
3-2. Results and discussions for the effects of wheel edge/surface features on faulty cut surface.　p.32
3-2-1. Sample and experimental conditions　p.32
3-2-2. Results and discussions　p.32
（1） Edge and surface features of a new scribing wheel.　p.32
（2） Relation between median crack surface roughness and the wheel surface features.　p.34
（3） Relation between median crack surface roughness and used wheel surface features.　p.36
（4） Relation between lateral crack formation and chipping　p.41
（5） Relation between fiber shape chipping and initial indentation condition of scribing wheel.　p.43
4. Conclusion　p.45
5. References　p.46

Chapter4 Quantitative evaluation of the cuttability of LCD glass substrate using four-point bending test
1. Introduction　p.47
2. Experiments　p.48
2-1. Samples　p.48
2-2. Preparation of scribed specimens　p.48
2-3. Four point bending test　p.49
3. Results and Discussions　p.50
3-1. Median crack depth vs. scribe load　p.50
3-2. Four point bending test　p.51
3-3. Influence of table stiffness　p.57
3-4. Influence of internal sheet stress　p.58
4. Summary　p.60
5. References　p.61

Chapter5 Effect of scribing wheel dimensions on the cutting of LCD glass substrate
1. Introduction　p.62
2. Experiments　p.63
3. Results and discussions　p.63
3-1. Median crack depth created by various wheel　p.63
3-2. Fracture mechanics of median crack formation　p.65
3-3. Influence of wheel tip angle and wheel diameter for scribability　p.66
3-4. Influence of the wheel angle to the breakability　p.70
3-5. Influence of the wheel diameter to the breakability　p.72
3-6. Influence of interval time between scribing and breaking　p.73
4. Summary　p.74
5. References　p.74

Chapter6 Conclusions
Conclusions　p.76
Remained issues　p.80
Publications related to this study　p.81
Other publications　p.81

Appendix I History, and Manufacturing Technologies　p.83
Appendix II Fracture mechanics of median crack creation by scribing, 1　p.95
Appendix III Fracture mechanics of median crack creation by scribing, 2　p.99

　Scribing and breaking is used not only to cut Liquid Crystal Display （LCD） glass substrate, but also to separate the mother LCD-cell into actual device sized cells. Sometimes, the ease or difficulty of glass sheet cutting by this method is explained by the term "cuttability". This thesis describes the results of theoretical and experimental approaches to clarify the scribing/breaking mechanism for widely used non-alkaline LCD glass, and sheds scientific light on cuttability.
　Previous studies on crack creation and propagation in glass using a point indentation method were studied to examine its applicability to the scribing /breaking method. It is found that analytical method for point indentation is potentially applicable to analyze crack creation by scribing, and the residual stress is a key factor defining the ease of the crack propagation.
　Fracture analysis was adapted to cut glass samples collected from actual manufacturing plant to find causes of the faulty cutting. Four deterioration modes existed on the cut surface, which strongly depended on the scribe wheel edge features. These results teach us that clear-cutting strongly depends on wheel tip features.
　Cuttability of glass can be explained as a combination of scribability and breakability for glasses. Evaluation of the scribability was attained by measuring the median crack depth, and breakability was evaluated by measuring the breaking force of the scribed sheet by a four-point-bending test. It was found that breakability was strongly influenced by residual stress caused by scribing and residual stress was relaxed by lateral crack generation.
　The influence of scribe wheel dimensions on the cuttability was evaluated by the established method. An equation including wheel dimensional factors and material properties was derived to predict median crack depth as a function of scribing load. In addition to that, obtuseness of wheel edge affected the median crack depth. The influence of the wheel geometry to the breakability was experimentally studied, and it was found that the influence of tip angle to the lateral crack creation was larger than that of the wheel radius. The influence of the residual stress to the breaking force reduction was quantitatively analyzed. The residual stress reduced the breaking force approximately 50% until relaxation occurred by lateral crack propagation.