Sensitive And Expedited Measurement Method And Equipment Development Of Water Vapor Transmission Rate

The tendency of flexibility of display devices like organic light emitted diode(OLED)accelerates the development of thin film encapsulation(TFE).Thin film which protects the device from the water vapor and oxygen is closely related with the steady working life of devices.The limit of barrier performance should be less than 1×10^-6g/m²·day in order that the device can work 10000h stably.The time spent on the measurement of water vapor transmission rate(WVTR)affected the research and development cycle of TFE.So the sensitive and expedited measurement method and equipment development is a desiderate task of WVTR at present.The paper is committed to develop sensitive,expedited and accurate method,based on the mass spectrometry and model about permeation and detection,to detect the WVTR of thin film.(1)The model of static and dynamic measurement which are designed for different permeability detect based on the research of theory of gas permeation through thin film.The gas permeation measurement(GPM)equipment is designed under the model and includes permeant introduction,sample fixture,permeant detection,vacuum,barking and control to detect the permeability of thin film.(2)The polyethylene naphthalate(PEN)which is detected by commercial instrument MOCON following a NIST-traceable procedure is chose to calibrated GPM equipment and the limit of static and dynamic is 6.13×10^-4g/m²·day and 10^-7g/m²·day level respectively.The comparison about the relationship between permeation rate and upstream pressure under helium and water vapor shows the different permeability features about different gas permeation.(3)Under the research of permeation model,the peek rate of signal changes over time at static mode can forecast the steady permeation rate.Meanwhile,the static and dynamic permeation models are verified by fitting data of different permeation times,from which the reliability of forecast in different times and other related permeation data are given.Aim at the actual application scenarios,the sensitive and accurate characteristics of GPM system are proved through measuring and comparing the results of aging test.