컬러필터 용 폴리아크릴계 바인더의 광경화 거동 및 물성에 관한 연구

Abstract

Color filter(CF)는 liquid crystal display(LCD)의 color image에 직접적인 영향을 미치는 중요한 요소로서, polymeric binder, functional monomer, photo-initiator, colorant, solvent로 구성 된 color resist를 사용하여 photo-lithographic method로 형성된다. Color filter layer는 photo-lithography공정과 LCD제조공정에서 사용되는 용매와 열에 의한 박막의 변색과 손상을 막기 위해 내열성과 내약품성이 중요하게 요구 된다. 본 연구는 Color resist의 각 요소가 내열성과 내약품성에 미치는 영향을 알아보기 위해서 광경화 거동과 물성의 평가를 진행하였다. 경화 거동은 FTIR을 이용하였고, 경화된 박막의 특성은 TGA와 나노압입측정으로 조사하였다. 그리고 각 조성에 따라 형성된 박막의 내열성과 내약품성의 평가는 색 변화관찰(ΔE)을 통해 확인하였다. 그 결과, 두 종의 광 개시제 함량 비 조절로 경화 속도와 수율의 조절이 가능함을 알 수 있었다. 경화거동과 경화된 막의 물성은 모노머 관능기와 구조, 그리고 바인더 분자량의 영향을 받음을 확인 할 수 있었다. 또한, 열과 약품에 의한 칼라변화를 통한 내열성 내약품성이 모노머 backbone structure의 강직함과 바인더의 높은 분자량을 통해 향상 가능함을 알 수 있었고, 경화 수율의 증가가 아닌 모노머와 바인더에 의해 형성되는 network구조의 영향을 받음을 알 수 있었다. |A color filter is an important constituent for liquid crystal display panel because it directly defines the color image quality of the display. A Color filter’s pixel has a set of R,G,B color elements and is usually prepared by the photo-lithographic method using the color resist, which consists of polymeric binder, functional monomer, photo-initiator, and colorant. Among the many requirement properties, the major property of color filter layer is thermal and chemical resistance which is very important factor for the alignment layer formation step. Therefore, In order to increase thermal and chemical properties of color filter, color resist were formulated with various components. This work is to study on characterizing color resists film and relationship of monomer and binder structure to their cure behavior and mechanical properties. Two different types of photoinitiator, eight different monomers and three different molecular weight binders were employed to investigate their effects. The curing behavior of the photo resist formulation was analyzed by observing the decrease of the vinyl double bonds at 810cm-1 according to UV irradiation time. The mechanical properties were investigated by thermogravimetric analysis and nanoindentation. The thermal and chemical resistance were evaluated using chromatic change before and after the heat or chemical treatment. Isopropyl alcohol(IPA) and tetramethylammonium hydroxide(TMAH) were used for chemical resistance test. As a result, the curing rate and conversion of our photo resist formulations could be controlled by the composition of two types of photo-initiator, Irgacure907 and 819. The 1:1 content ratio of initiator system showed the best mechanical properties of cured film and was selected for the next experiments about the effect of monomer and binder structure. The curing behaviors and mechanical properties were dependent on the structure of monomers and the molecular weight of binder. Increasing the monomer functionality leads to higher curing rate and higher hardness. The rigidity of chemical backbone could improve hardness and thermal stability. The rigid backbone structure and steric hindrance by methyl group attached to vinyl group caused low value of conversion. In addition, increment of the molecular weight of binder leads to low value of conversion, low hardness and low modulus of cured film due to its disturbing effect on monomers cross-linking. The chromatic changes for thermal or chemical resistance are affected by the network structure combined by monomers and binders. The results of thermal or chemical resistant experiments showed that the highest curing conversion did not ensure the thermal or chemical resistant properties. The rigid backbone structure of monomer and higher molecular weight of binder polymer could improve the thermal and chemical resistance of color resist film.; A color filter is an important constituent for liquid crystal display panel because it directly defines the color image quality of the display. A Color filter’s pixel has a set of R,G,B color elements and is usually prepared by the photo-lithographic method using the color resist, which consists of polymeric binder, functional monomer, photo-initiator, and colorant. Among the many requirement properties, the major property of color filter layer is thermal and chemical resistance which is very important factor for the alignment layer formation step. Therefore, In order to increase thermal and chemical properties of color filter, color resist were formulated with various components. This work is to study on characterizing color resists film and relationship of monomer and binder structure to their cure behavior and mechanical properties. Two different types of photoinitiator, eight different monomers and three different molecular weight binders were employed to investigate their effects. The curing behavior of the photo resist formulation was analyzed by observing the decrease of the vinyl double bonds at 810cm-1 according to UV irradiation time. The mechanical properties were investigated by thermogravimetric analysis and nanoindentation. The thermal and chemical resistance were evaluated using chromatic change before and after the heat or chemical treatment. Isopropyl alcohol(IPA) and tetramethylammonium hydroxide(TMAH) were used for chemical resistance test. As a result, the curing rate and conversion of our photo resist formulations could be controlled by the composition of two types of photo-initiator, Irgacure907 and 819. The 1:1 content ratio of initiator system showed the best mechanical properties of cured film and was selected for the next experiments about the effect of monomer and binder structure. The curing behaviors and mechanical properties were dependent on the structure of monomers and the molecular weight of binder. Increasing the monomer functionality leads to higher curing rate and higher hardness. The rigidity of chemical backbone could improve hardness and thermal stability. The rigid backbone structure and steric hindrance by methyl group attached to vinyl group caused low value of conversion. In addition, increment of the molecular weight of binder leads to low value of conversion, low hardness and low modulus of cured film due to its disturbing effect on monomers cross-linking. The chromatic changes for thermal or chemical resistance are affected by the network structure combined by monomers and binders. The results of thermal or chemical resistant experiments showed that the highest curing conversion did not ensure the thermal or chemical resistant properties. The rigid backbone structure of monomer and higher molecular weight of binder polymer could improve the thermal and chemical resistance of color resist film.