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급속가열 및 압축의 효과가 7인치 도광판의 복굴절 분포에 미치는 영향에 관한 실험적 연구
민인기(I. K. MIn),홍석관(S. K. Hong),강정진(J. J. Kang),김민구(M. G. Kim),정의철(E. C. Jung),윤경환(K. H. Yoon) 한국소성가공학회 2012 한국소성가공학회 학술대회 논문집 Vol.2012 No.5
As the growth of injection molding technology, injected-molded optical products require higher dimension accuracy and optical stability than ever. In the present study, four kinds of molding mechanisms, i.e., conventional injection molding(CIM), injection/compression molding(ICM), rapid heat and cooling the mold(RHCM) and rapid injection/compression molding(RICM) were chosen to investigate the optical anisotropy of 7 inch LGP by examining the in-plane and gap-wise distribution of birefringence and extinction angle. As a result, the compression process could decrease flow-induced birefringence for the whole region and rapid heating could decrease the birefringence level than conventional molding mechanism. Finally, for the combination of compression and rapid heating, the reversal flow was detected from the distribution of extinction angle near the gate.
정밀 광학부품의 복굴절 분석을 통한 각종 성형법의 영향에 관한 연구
민인기(I. K. Min),윤경환(K. H. Yoon) 한국소성가공학회 2012 금형가공 심포지엄 Vol.2012 No.9
As the growth of injection molding technology, injected-molded optical products require higher dimension accuracy and optical stability than ever. In the present study, four kinds of molding mechanisms, i.e., conventional injection molding(CIM), injection/compression molding(ICM), rapid heat and cooling the mold(RHCM) and rapid injection/compression molding(RICM) were chosen to investigate the optical anisotropy of 7 inch LGP by examining the gap-wise distribution of birefringence and extinction angle. As a result, the compression process could decrease flow-induced birefringence for the whole region and rapid heating could decrease the birefringence level than conventional molding mechanism. Finally, for the combination of compression and rapid heating, the reversal flow was detected from the distribution of extinction angle near the gate.
사출 및 사출/압축이 투명 디스크의 복굴절 분포에 미치는 영향에 관한 실험적 연구
민인기(I. K. Min),이경범(K. B. Lee),윤경환(K. H. Yoon) 한국소성가공학회 2009 한국소성가공학회 학술대회 논문집 Vol.2009 No.10
Recently, injection/compression molding process became more popular than ever to produce many transparent optical products of high precision. Especially, optical disk for read/write is the best example. But those optical disks can cause sensorial problems because of high birefringence or deformation from the residual stresses in the media. Therefore, it is necessary to study the effects of various process conditions on the final birefringence structure in injection-only and injection/compression molded disks for producing precision injection-molded products. In thd present paper we have focused on the effect of injection, holding and compression processes on the optical anisotropy(i.e. birefringence) remaining in the MOD by examining the gapwise distribution of birefringence and extinction angle. The effect of holding pressure was found to form the inner two birefringence peaks. But the effect of compression pressure on the birefringence distribution was found to make the uniform distribution near the center in the gapwise direction and inversion of extinction angle far from the gate.
50μm급 마이크로렌즈 적용 2인치 휴대폰 LCD-BLU 금형 개발 : 광학패턴의 세장비 영향
김종선,고영배,민인기,유재원,허영무,윤경환,황철진,Kim, J.S.,Ko, Y.B.,Min, I.K.,Yu, J.W.,Heo, Y.M.,Yoon, K.H.,Hwang, C.J. 한국소성가공학회 2007 소성가공 : 한국소성가공학회지 Vol.16 No.1
LCD-BLU(Liquid Crystal Display - Back Light Unit) consists of several optical sheets: LGP(Light Guiding Plate), light source and mold frame. The LGP of LCD-BLU is usually manufactured by etching process and forming numerous dots with $50{\mu}m$ in diameter on the surface. But the surface roughness of LGP with etched dots is very high, so there is much loss of light. In order to overcome the limit of current etched dot patterned LGP, optical pattern design with microlens of $50{\mu}m$ diameter was applied in the present study. The microlens pattern fabricated by modified LiGA with thermal reflow process was applied to the optical design of LGP and optical simulation was carried out to know tendency of microlens patterned LGP simultaneously. The attention was paid to the effects of different aspect ratio(i.e. $0.2\sim0.5$) of optical pattern conditions to the brightness distribution of BLU with microlens patterned LGP. Finally, high aspect ratio microlens patterned LGP showed superior results to the one made by low aspect ratio in average luminance.
박형 광학제품의 복굴절 예측을 위한 투명 수지의 광점탄성 계수 측정에 관한 연구
민인기(I. K. Min),윤경환(K. H. Yoon) 한국소성가공학회 2012 한국소성가공학회 학술대회 논문집 Vol.2012 No.10
In the present study, rheo-optical and mechanical properties of amorphous polymers (PS, PC and COC) widely used in optics and engineering field have been investigated. Accurate measurements of stress/strain-optical coefficients and elastic modulus data across the glass transition region are essential for predicting optical anisotropy in many optical products like pickup lenses and light guide plate(LGP) in LCD module since the final products have both flow and thermal history from the melt to glass. To obtain stress-optical behavior in wide range of frequency including rubbery, glassy and glass transition regime, shear sandwich and extensional bar were used in frequency sweep mode. As a result, the storage stress-optical coefficient of polystyrene(PS) showed the sign change as the frequency increased. On the other hand, the sign of stress-optical coefficient over the whole frequency region is always positive for polycarbonate(PC). For COC, it showed lower level of stress-optical coefficient than PC and PS.
2.5인치 도광판의 게이트 자동절삭 및 사출/압축성형법을 이 용한 사이클 타임 저감에 관한 연구
민인기(I.K. Min),김종선(J.S. Kim),고영배(Y.B. Ko),허영무(Y.M. Heo),신광호(K.H. Shin),윤경환(K.H. Yoon) 한국소성가공학회 2011 금형가공 심포지엄 Vol.2011 No.9
Currently conventional injection molding system of extremely thin-wall parts such as LGPs (Light Guide Plates) for mobile display reaches the limit due to frozen layer and the critical speed of injection. The melted polymer in the cavity is rapidly frozen because of high heat flux from injected polymer to mold base. To overcome these problems various attempts have been studied such as RHCM, ICM, ultra high speed injection molding assisted by high pressurized gas, etc.. In the present study, injection/compression molding was applied to form a thin wall parts. Futhermore, to decrease the cycle time for production, a novel mold system was proposed including automated gate cutting mechanism. As a result, productivity of part was increased to 40% higher than usual and cycle time was decreased to 10 sec under.