| Electronic paper display technology has the advantages of ultra-low power consumption,flexibility,and eye protection,and is widely used in fields such as electronic readers,smart retail,smart office,smart healthcare,and smart home.The longer lifespan for the of electronic paper display screens is required with the application and promotion of electronic paper in the field of the Internet of Things（Io T）.The existing packaging technology for microcapsule electrophoresis display cannot meet this lifespan requirements.This thesis focuses on the packaging materials,structures,and manufacturing parameters of microcapsule electrophoresis display devices.Their impact on the optics,electricity,and reliability of display devices is studied.Innovative testing methods for the optical,electrical,and reliability performance of microcapsule electrophoresis materials are proposed,and relevant international and national standards are formed.A new life prediction model for display devices was proposed based on test data,and a new packaging structure was designed and its reliable performance was verified.It was proved that the new structure can extend the product’s service life.The impact of different packaging structures on lifetime for flexible and color displays in future was evalμAted,and key process parameters and window values that affect optical performance and reliability were found.The main research content is list as follows:Optical and electrical testing and life prediction issues for microcapsule electrophoresis display materials were set up.A testing method for characterizing the electrical properties of microcapsule electrophoretic display materials was established,and an optical testing method for electronic paper display screens was developed base on the color system of CIE1973L*a*b*system.The corresponding relationship between the current change（from 5-6μA to170μA）and the optical performance change of the display material in high-temperature and high humidity storage were found.Development of international IEC electronic paper standards and led the development of national standards for electronic paper display devices were done during this period as a technical expert.These standars are in approval stage currently.Four models for predicting the display life of electronic paper were verified ccording to the data validation of high temperature and humidity test,and LWW model was selected as the life prediction model of microcapsule electrophoresis display device.The impact of key packaging materials such as protective film and edge bonding adhesive on optical performance and reliability was studied,and the adverse phenomena caused by packaging materials were analyzed.In response to the failure phenomenon of existing microcapsule electrophoresis display devices in client applications and reliability testing,ultrasonic microscopy was used as a microscopic analysis method to analyze the micro changes in their packaging structure,and the failure mechanism was revealed from the display principle.It was found that water vapor intrusion was the main cause of failure.Another reason is that the packaging structure has changed significantly due to the micromechanical deformation of the coefficient of thermal expansion of the material during the temperature change process,leading to the failure of its devices.The impact of different packaging structures on the reliability performance of display devices was studied.The hard screen packaging structure of glass substrate is improved.The effective packaging distance at the edge position was increased,and it indicated the reliability performance of display devices.,The effect of different effective edge sealing distances on the reliability performance of the device was tested,and the minimum packaging width was found to be no less than 0.8mm;impact of different flexible display device packaging structures on reliability performance is studied.In response to the long-term requirements of Io T application products for microcapsule electrophoretic display devices,a new packaging structure based on its failure mechanism is proposed.Under the premise of meeting the requirements of process and cost,a new packaging structure is adopted to extend the failure time of display devices in high temperature and high humidity testing by more than three times.According to the theoretical calculation of the LWW model for life prediction,the product life is doubled with this structure.The protection against water vapor is strengthened on the packaging material.The water vapor transmittance of optical glass is lower than 10-6g·m-2·day-1,which is far lower than the 10-2 g·m-2·day-1 of the existing waterproof functional film;Compared with the coefficient of thermal expansion（average value of 23-100℃）of60×10-6m/（m.k）of traditional PET substrate,the coefficient of thermal expansion of glass is about 10-7m/（m.k）.The optical transmittance of glass material is higher than 90%,while the optical transmittance of water vapor barrier of PET substrate is not more than 88%,which can improve the optical performance of the product.At the same time,optical glass has cost advantages over water vapor barrier,the cost of the product is reduced.The impact of processing parameter on optical performance and reliability was studied,and bonding temperature and pressure are important process parameters that affect the optics of display devices are found t.DOE experiments showed that the higher the temperature（80℃）and bonding pressure（0.3Mpa）during the bonding process,the optical performance is better.Through DOE experiments on temperature,pressure,and temperature rise curves during the process of defoaming and edge bonding adhesive curing,the effects of different process conditions on reliable performance were discovered,and the optimal process parameters were determined.The new microcapsule electrophoretic display device developed in this paper has been widely used in electronic price tags,smart home products,and smart bus stop signs,with over 1million pieces shipped in bulk.After practical product application scenarios,it has been proven that the structural performance is stable and reliable,and can meet the application requirement of IoT products. |
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