Patent number 8729472 is assigned to
The following quote was obtained by the news editors from the background information supplied by the inventors: "One important characteristic of certain materials, such as plastic barrier films, is the degree to which certain substances, such as gas and vapors, permeate the materials. In certain applications, such as use in photovoltaic electronic devices, low permeation rate to water vapor results in higher shelf life and thus contributes to lower cost. Water vapor transmission rate (WVTR) is a widely used measurement for determining the barrier properties of a plastic film. It is a measure of the amount of water vapor that can permeate through a certain area of a film over a certain period of time. WVTR is one of the key properties in photovoltaic, organic light emitting diodes (OLED) and other electronic devices. One target for commercialization and longevity is water vapor permeation rate in the range of 10.sup.-6 g/(m.sup.2-day).
"Systems, such as the Mocon Aquatran, use a coulometric phosphorus pentoxide sensor that converts water vapor to an electrical charge. Those systems can detect moisture down to the level of 5.times.10.sup.-4 g/(m.sup.2-day). Below this level, the coulometric technique is inadequate.
"Some laboratory methods, such as the so-called calcium method, exist that can measure water vapor below 10.sup.-4 g/(m.sup.2-day) using the optical transmission or the electric conductivity of a calcium coating which is encapsulated within a cell that is sealed with the barrier sample of interest. The calcium method, however, is typically laborious and the use of the method has not yet been standardized. Furthermore, the degradation of calcium is a function not only of the permeation rate of water vapor but also due to permeation of other species especially oxygen. In addition, the evidence to date does not confirm that the calcium method can actually measure WVTR as low as 10.sup.-6 g/(m.sup.2-day). Thus, these systems are not sufficient for measurement of barrier properties for ultra-barriers designed for photovoltaics, OLED and other electronic devices.
"Therefore, there exists a need for a gas permeation measurement technique which is simple, easy to use, has the ability to analyze for a specific molecule such as water, and has a low detection limit."
In addition to the background information obtained for this patent, VerticalNews journalists also obtained the inventors' summary information for this patent: "The present invention is directed to systems and methods which utilize a wavelength-tuned cavity ring-down spectroscopy (CRDS) technique implemented for the measurements of vapor transmission rate through a barrier film. In one embodiment, the vapor content to be measured is placed within an optical cavity. Light is then injected into the cavity up to a threshold level and the decay time of the injected light is measured. When the wavelength of the injected light is resonant with an absorption feature of the vapor the decay time of the cavity decreases as a function of vapor content. In this manner, vapor content reduces decay time and thus the amount of vapor passing through the film (film permeation rate) can be determined in real-time.
"In one embodiment, water vapor is measured in a pass/fail mode where the film fails if the decay time of the light is less than a threshold (high moisture content) and the film passes if the decay time is longer than a given threshold. If desired, the threshold parameters can be adjusted from time to time based on the samples being tested by other measurement techniques acting as a calibration on the production system.
"The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention."
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Keywords for this news article include: Electronics, Photovoltaic,
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