Engineered Film Development for Commercial & Emerging Applications

Engineered Film Development for Commercial & Emerging Applications

Metallized polymer films are widely used in diverse commercial applications including flexible packaging, reflective insulation, graphics, durable labels and electronics. Wide adoption of aluminum, copper, and metal oxide coated films has been accelerated by their cost effectiveness and functional properties as light weight vapor barriers, thermal and specular reflectors and transparent electrical conductors. Manufacturing efficiency is supported by relatively low material costs and high throughput (1000 ft./min.) roll to roll, vacuum metallizing systems.  Vacuum metallized polyester or polyethylene films are flexible packaging materials of choice because they preserve freshness by providing very good oxygen and moisture barriers. Generally, barrier properties are created via the deposition of 25 to 50 nanometer aluminum or aluminum oxide layers deposited onto 25 to 100 micron extruded films using roll to roll metallizing or PVD sputtering systems. Decorative metallized films are used in the graphics and label industries primarily for their aesthetic and specular reflective properties. Secondary functionality is achieved by the addition of adhesives and printable top coatings applied to the metalized films as they are converted into final product configurations.  

Aluminum and copper metallized films and foils possess visible and infrared reflective properties, making them ideal for commercial reflective insulation. In addition to providing vapor barriers in buildings, aircraft and other structures, metallized IR reflective window films reduce thermal transfer by reflecting the dominant portion of the infrared spectrum. Conversely, radiant barrier materials emit very little thermal energy. Energy transfer properties are typically measured in emissivity and reflectivity values ranging from 0 to 1; where a perfect reflector has an e value of 0 and a perfect emitter (e.g. blackbody radiator) has a value of 1. Metallized polyimide films are widely used in aerospace applications due to their ability to provide exceptional insulting properties and mechanical durability over a wide thermal range.

The conductive properties of aluminum, copper and transparent oxides deposited on films enables more specialized applications including the fabrication of electronic displays, flexible circuits, battery current collectors, photovoltaics, RFID tags, electro-chemical medical diagnostics, smart windows, and transparent heaters. In all cases, the metallic layers add electrical, physio-chemical and environmental properties to enhance functionality.  

Metalized, coated and laminated films are widely used in rigid and flexible display and touch screen manufacturing, customization, and enhancements.   As shown in Table 1, functional properties such as O2/H2O barriers, visible and IR reflection are also important in many electronic applications. In addition, metallized films can be manufactured to provide electrical conductance, electro-static discharge (ESD) and electro-magnetic and radio-frequency interference (EMI/RFI) shielding. Patterning of metallic films via photolithography and laser etching enables these materials to be used in Radio Frequency Identification Tags (RFID) used in Near Field Communication (NFC), 5G antennas and other growing wireless Internet of Things (IoT) applications. Stamped foils and printed conductive inks can also be used to produce these materials.    

Many of today’s emerging technologies are enabled by the metallization and photolithographic patterning techniques developed in the manufacturing of liquid crystal displays and semiconductor chips. These include a variety of specialized films processes used in the production and enhancement of commercial off the shelf (COTS) displays, touch screens and vision systems:     

·        Specular Reflector Films – backplanes used in Light Emitting Diodes (LED’s), Organic Light Emitting Diodes (OLED’s), Cold Cathode Fluorescent Lighting (CCFL) and LED lighting systems to increase luminance without using more power or generating more heat.

·        Brightness and Dual Brightness Enhancement Films - (BEF and DBEF) are transparent and translucent light control films used to direct emitted display light and to improve LCD viewing angles and contrast.

·        Diffuser Films – silica microspheres are embedded in polymer film surfaces modify the properties to emitted light to reduce “hot spots” due to point source LED’s. 

·        Encapsulation Films - In both rigid and flexible LCD’s, films are used to encapsulate and protect the liquid crystal materials. Low moisture and oxygen transmission rates are required to prevent degradation of the liquid crystals.

·        Antireflection Films – thin film coated and textured films are used to reduce and scattered surface reflection and enable better image transmission and display contrast.

·        Transparent Conductive Films – metallic and metallic oxide materials are vacuum deposited on clear polyester, olefin, triacetate, polyimide films to provide the active layers of electronic displays and touch screens.  

·        Insulating Films – films used to reflect or absorb IR energy to dissipate thermal loading from electrical components or solar loading. Used in a wide range of commercial, industrial, and aerospace applications. Dielectric insulators are also used in displays.

·        Prismatic Films – holographic patterns used to create 3D images or for authentication

·        EMI/RFI Shielding Films – optical and non-optical metallic films used reflect or absorb radiated emissions or external radio or electro-magnetic energy.

·        Patterned Metallized Films – copper and aluminum conductive grids used for transmitting and reflecting radio and electro-magnetic frequencies for NCF, RFID and 5G applications.

·        Security Films – various embossing, metallizing and taggants are incorporated into the film structure to provide authentication and anti-counterfeiting features.

·        QD Films – Quantum dot films constructed with red, green blue QD’s to enhance color saturation of displays or UV reflective properties for security applications.

·        NVIS Films – extruded polymer films with specialized dyes to absorb NIR energy for night vision display system operations.  

The applications for these light weight, cost effective films are sizable and growing in-line with the growth of electronic display and communication applications associated with the proliferation of mobile devices, signage, gaming, entertainment and defense applications. As shown in Figure 1, in addition to the initial fabrication of electronic devices, metallized and coated films are used to adapt displays and touch screen to perform better in demanding applications such as direct sunlight, high or low temperatures or rugged environments.    

Metalized, insulting and encapsulating films are used in adjacent markets such as lighting, photovoltaic modules and flexible circuits manufacturing. For instance, specular reflector films are used in LCD backlighting systems (to improve sunlight readability), as well as commercial LED luminaires. Insulating and IR reflectors used in fast growing aerospace applications such as CubeSATs are also used to improve thermal loading on flexible and foldable displays and wearable electronics for biometric monitoring. Incorporating metallized and coated films into demanding new applications has been driven by market demand and realized by successfully scaling the development of new film, coating and processing technologies.

Roll to Roll Film Technology in New Product Innovation  

Designing and integrating metallized films and their mechanical, thermal, electrical and optical attributes into new products are facilitated by initially focusing on materials with known properties and that are commercially available in prototype quantities.  In order to optimize the functionality of flexible substrates, it is important to understand and define the physical and mechanical characteristics of the base film, intermediate products and what is needed in final product configuration.  For instance, performance attributes of flexible films used in display manufacturing and enhancement include high transmissivity or reflectivity, high and low temperature resistance and, if they are used for front surface applications, high scratch and abrasion resistance.  For optical and performance testing, the films can be incorporated into displays with testing protocols conducted before and after integration.  Performance testing is conducted using a variety of mechanical, optical and electrical test equipment, as well as environmental test chambers to characterize and verify the durability of the films and coatings prior to incorporation into final product configurations:

Ø Dielectric Properties – resistance ad conductance values of the base film substrates

Ø Emissivity Values – properties of thermal emission of the film

Ø Thermal Range - 40 to +85 deg. C for displays; -200 to +500 deg. C for aerospace

Ø Humidity Resistance -  95% relative humidity @ 95 deg. F (H2O absorption properties)

Ø Hard coating scratch resistance – pencil test should meet 3H or 4H

Ø Hard coating abrasion resistance – Taber Abrasion Test (per ASTM D4060)

Ø Transparency – > 90% transparent (for PET, PMMA, TAC films)

Ø Haze - <2% haze, ideally less than 0.5% for transparent application

Ø Gloss level (ASTM D523)

Ø UV resistance – QUV testing to determine durability under accelerated weathering

Ø Metallization thickness (typically 100 to 1000 angstroms)

Ø Resistance – ohms or milliohms/sq.

Ø Reflection – using a spectrophotometer measured at 0, 15, 30 degrees

Ø Chromaticity – CIE or LAB color index

Ø Coating adhesion – tape test, cross hatch test

Ø Dyne Level – of base film to ensure good adhesion of metallization, coating, printing

Ø Hydrophobic coating – reduce surface contamination; ideally > 110 deg. contact angle

For initial development, some batch and lab-scale coating chambers can evaporate or sputter at lower temperatures on films and serve to model the coating design and functionality on polymer substrates prior to scale up on more expensive inline or roll to roll systems. For volume applications, polymer films are typically coated on multi-million dollar roll to roll magnetron sputtering or vacuum metallizing systems in widths up to three meters. 

Utilizing Design of Experiments (DOE’s) for initial development enables researchers to build on the functionality of a Minimally Viable Product (MVP) to compress both innovation timelines and life cycle testing. MVP’s possess basic product features sufficient to attract early adopter customers and can be expanded to meet more demanding requirements.  For instance, organic and inorganic barrier coatings with known properties used in a general packaging application can be incorporated into higher durability fluoropolymer film laminations for photovoltaic and display applications. However, product durability must be verified suitable for the application, environmental conditions and life-cycle.  

In scaling new product designs, developing a rigorous Acceptance Test Plan (ATP) is crucial in establishing the material acceptability prior to promoting a commercial product for more demanding aerospace or military applications. It should be noted, in the case of military and aerospace materials, that qualification costs of new materials are often significant and, therefore, may prohibit new materials being introduced prior to initiating a design change. Likewise, the properties of the metallized coatings, long term durability, as well as the technical data and certifications of the base substrates should be considered in product design and positioning of polymer films where processing temperatures of coating, metallizing and laminating operations are critically important.  

Testing and Validation

In addition to establishing baseline data on individual components, it is important to determine the functional properties of combined materials. For flexible metallized substrates, additional coatings, adhesives, colorants and inks intended to add functionality, may alter mechanical, flame resistance, thermal range or other properties. To this extent, laminates or composite structures should be tested to simulate real world product usage. Research has shown that product failures often occur due to multiple stresses. For outdoor applications these stresses can be simulated via accelerated weathering such as damp heat (85 deg. C/85% humidity) combined with UV light and mechanical stress for durations ranging from 1000 to 3000 hours. These tests are very useful for validation of photovoltaic or aerospace materials that need to last outdoors or in space without degradation for decades. Similarly, thin film metalized substrates used in Li-ion battery construction, need to be precisely coated and manufactured defect free to preserve safe operation. Due to the significant liability of long term product warranty issues, selecting proven materials such as UV and hydrolysis resistant films, foils, coatings and adhesives is imperative. Preceding the scale up process, lab testing can validate design and demonstrate product robustness, while field testing provides extremely valuable customer feedback. Similarly, with sustainability as topic of product focus, the biodegradability of polymer films is important is packaging and consumer applications.  

Scale Up, Costing and Commercialization

Once a product has been laboratory and field tested. As shown in Figure 1 Product validation moves to pilot production, as the next critical gate in the development process. With flexible metallized films coated via a R2R process, metallization thickness, web tension, process temperature, coating weight and drying temperature are all critical parameters. A pilot coating trial conserves material and time and provides insight on how well the materials and processes will scale on production systems. Once the pilot stage gate is completed, scale up manufacturing methods, efficiency, throughput and product quality become the focus.

Commercial viability in NPD requires the product to meet cost objectives and launch dates; being on time and within budget. On the process side, Design for Manufacturing (DFM), the ability to produce a robust product is equally important, as well as safety, waste minimization and robust supply chain integrity. Societal trends such as sustainability, recyclability, volatile organic compounds (VOC’s) reduction and solvent free lamination methods, are also considerations in flexible material selection and manufacturing methods.

In production, costs are primarily driven by raw materials, capital equipment investment and manufacturing efficiency including production speed, scrap and rework. Many new, potentially promising products, never move to the commercial stage because they cannot meet the cost objectives outlined in the business case or provide sufficient product value for a pricing premium. Invariably, successful commercialization includes process optimization, “cost down” material improvements, and in some cases, capital investment to meet market pricing.  The return on investment for film R2R metallization and coating systems is ultimately tied to initial system investment, throughput and ancillary manufacturing support services. From a material perspective, thinner “down gauged” substrates and are often used for material conservation. On the manufacturing side, process engineering can often improve machine speeds, product yields, quality and throughput. Leveraging film metallization system selection expertise with process optimization will generally increase the chances of technical and commercial success in NPD.  

Market Access & Support

Collaborating with experienced film metallization and coating system manufacturers and coating suppliers can usually reduce the costs, timelines and risks associated with integrating metallized films into new products. Additional benefits of collaborative development is generating referral and support for upstream and downstream supply chain needs for new products. In this case, coating system manufacturers, substrate suppliers, converters, coaters, laminators and distributors all fulfill different niches within the marketplace. Consequently, new products can be sold into different market segments, and in various configurations and quantities based on end-user requirements.

In summary, the metallized film systems, materials, and tests outlined in this article provide a proven process for adding functional properties to new materials used in industrial, aerospace and commercial applications. The key in collaborative innovation is to select development partners that have a deep “Technology Toolbox” and material science expertise to support innovation, compress R & D project timelines and reduce costs. At the same time, a partner with the film metallizing and coating systems and expertise to scale up and commercialize new technology is invaluable in turning product design concepts into new products and commercial successes.