The Mass Spectrometry Measurement Of Gas Permeability Of The Packaging Material

Organic Light-emitting diodes （OLED）, because of its active light-emitting, wideviewing angle range, fast response, rich colors, high resolution, thin, low powerconsumption and many other advantages, has been widely used in the display area. It isthe new-generation flat panel displays, and has the most development potential afterliquid crystal display （LCD）. To play the role of the main force of the display sector,OLED must achieve industrial which has to overcome a lot of problems. One of themain problems is lifetime below standard. Seen by the failure mechanism of the OLED,the main problem is that water vapor and oxygen could damage the organic lightemitting layers, then affect the stability and lifetime of the OLED device. The watervapor and oxygen of the device which penetrate the device packaging materials into thedevice are mostly come from the atmosphere outside. Therefore, to make the lifetime ofOLED devices to reach the level of commercialization, one hand, it is required organiclight emitting materials which have good stability, and another important aspect is thestudy water, oxygen and other reactive gas barrier properties of the encapsulationmaterial. For these reasons, we do the following research:（1） Made more detailed analyses of the short lifetime for OLED devices failuremechanism, and explained the importance of barrier ability of the packaging materialsto the activity of water, oxygen and other gases. We shortly introduced the commonpermeability measurement method by consulting large amounts of relevant literatures,and then we compared the characteristics of the various methods.（2） In the work, we introduced the gas percolation theory and the relevant vacuumtechnique theories of mass spectrometry to measure the gas penetration coefficient indetail. Meanwhile, we explained the principles and characteristics of the core structureof the experimental system （quadruple mass spectrometer）.（3） In this work, we used dynamic sampling method to measure the gas penetrationcoefficient by building the mass spectrometry measurement experimental system. Themain work of this experiment were measured the oxygen and water vapor permeabilityof the PET film and the UV plastic film which was commonly used as OLED packaging material, and analyzed the barrier performance against water, oxygen, and provided areference to determine the accuracy of the data from subsequent static method.（4） Based on the dynamic mass spectrometry measurement system, established thestatic accumulation type mass spectrometry experiment system to measure gaspermeability, and used the system to measure water vapor and oxygen permeability ofPET film by analyzing its data collection and calculation method and the key factors.Furthermore, we compared the results with the data from dynamic method, to verify thereliability of the static accumulation method and the data collection and calculation.（5） Used the static accumulation injection mass spectrometry measurement systemto measure water vapor permeability of mica film with high barrier materials forflexible OLED encapsulation. Mica film has high barrier properties, thenaccumulation-room background outgas was larger than permeability. In order toaccurately distinguish the background outgas and penetration amount, experimentallyused isotopes of ordinary water （heavy water） instead of ordinary water to measure thewater vapor penetration of mica film. Heavy water vapor permeability of50μm thickmica film was2.3105g/（m²day）.（6） Used the static accumulation Mass Spectrometry to measure heavy water vaporpermeability of PET film. The result was2.35g/（m²day）. In contrast to the ordinarywater vapor permeability of PET film, verified the reliability of the heavy water insteadof ordinary water. The results are consistent.（7） Re-estimated the limit sensitivity of the improved system. The dynamic massspectrometry limit sensitivities to water vapor and oxygen were6.77×10^-7g/（m²day）,and9×10^-4cm3/（m²day）, respectively. Static accumulation mass spectrometry limitsensitivities to water vapor, heavy water vapor and oxygen were3.30×10^-5g/（m²day）,2.72×10^-8g/（m²day）, and7.88×10^-6cm3/（m²day）, respectively.