The ability to resist the penetration of moisture and gasses is vital for many types of products, including pharmaceutical products (e.g., capsule blister-packs), food packaging, and electronics (such as OLED, quantum dots and photovoltaic applications). Moisture barrier materials are normally applied as coatings or membranes to help protect these and other products from being compromised.
The degree of moisture barrier required varies for each type of product. Food packaging requires a relatively low moisture barrier quality to prevent spoilage. Pharmaceutical products require higher barrier levels (allowing less moisture and oxygen to penetrate). The highest-level barriers are needed for electronics applications, which are extremely sensitive to moisture and gasses.
Permeability is measured in terms of the amount of water, vapor or gas that penetrates the barrier through 1 square meter (or sometimes 100 in2) of substrate. A measure of permeability is expressed as 1×10-1 = .1 g/m2/day, or 2×10-3 = .002g/m2/day of moisture getting through the barrier.
Pharmaceutical packaging tends to use films with permeability measured in cc’s per square meter, per day of oxygen or grams of moisture getting through the barrier; or described as WVTR (water vapor transmission rate) in grams per day. Barriers for this type of packaging tend to be in the 10-1 to 10-2 or 0.1-0.01 range. Barrier materials are tested using precision equipment where specific temperature and humidity conditions are applied to the substrate on one side of a chamber, and measurement occurs on the other side. MOCON is a manufacturer of such equipment that operates in accordance with established, industry-accepted methods for both sample preparation and analysis.
Electronics are highly sensitive to oxygen and moisture, so they need high barrier quality with permeability in range of a 10-4 to 10-6 target, depending on the materials or device. OLED applications drive the greatest need for high barrier properties in the 10-6 range to achieve long product life.
Glass is a perfect barrier, but there is desire to replace it because it is heavy, inflexible and expensive, and it can break. Flexible barriers offer new form factors (curved, bendable, foldable, etc.). To replace glass, high barrier materials are needed with high optical qualities. Material with a high percentage of light transmission, represented as %T, will allow for more efficient use of light (whether into the panel for PV, or out of the device for OLED or QDEF films for LCD). The high barrier will enable acceptable performance over the lifetime of the product.
Polymer-based barrier solutions can use alternating layers of pairs of thin films, such as organic/inorganic, inorganic/inorganic and nanoparticle/inorganic layers. Barrier performance (impermeability) tends to improve with multiple layers.
Carestream Contract Manufacturing offers high-quality multi-layer precision coating – a good fit for application of both pharmaceutical barriers in the 10-1 to 10-2 range and mid- to high-performance barriers such as 10-4 to 10-6. The precision coating methods and 100% automated optical inspection used by Carestream help avoid pinholes that can quickly degrade barrier performance.
Typically multi-layer structures need an under-layer or topcoat to protect the vapor-coated barrier. The under-layer is a planarization layer that makes the substrate smoother for superior vacuum coating uniformity and better barrier. Carestream’s clean room and precision coating assets offer enhanced uniformity, which is especially important with electronics applications. Our multi-layer coating capability allows greater efficiency with fewer passes on coating machines.
Barrier coatings and membranes can be applied in a few different ways. The dyad approach creates a “torturous path” with alternating layers of organic and inorganic materials; each combination is called a dyad. A barrier might have 4-10 layers, which create a torturous path for each water molecule trying to get through.
Some barrier layers are applied in straight vapor deposition, some as liquid barriers. It is sometimes possible for product packagers to partner with a coating specialist, such as Carestream, and co-locate the processes. For example, a customer might bring vapor vacuum deposition operations to Carestream’s facility, where we would put down the planarization layer and/or the topcoat or organic layers in a dyad approach that uses alternating vacuum deposited inorganic layers with atmospheric coating of organic layers.
A company with a product application requiring multi-layer barrier coating (3-20 layers) can save significant time and money by partnering with Carestream and using our clean-room facility to coat multiple layers at once.