Bigger, Stronger Program for Liberty® Slot Dies Translates into New Capabilities for Flat Panel Display Manufacturers
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Now Owner EDI Has Expanded Access to a Coating Process with Many Advantages over Roll Coating and Added Options for Trial Runs, Product Development, and Product Innovation
LOS ANGELES, May 18, 2008: At SID 2008, Extrusion Dies Industries, LLC (EDI) is highlighting a range of new capabilities for slot die coating, the high-precision process employed by companies that apply materials to the surfaces of film layers in flat panel displays (FPDs). Users of EDI's Liberty® slot die coating systems now have available cost-saving alternatives for trial runs and product development, advanced technologies for adding functions to a single coating application, and new global sourcing options for companies that manufacture in many countries, according to Dennis S. Paradise, vice president of sales and marketing (Booth 142).
These developments have emerged as part of EDI's response to growing demand for slot die coating as a replacement for conventional roll coating, Paradise said. "As a closed system in which the amount of coating material is pre-metered by a precision pump, slot die coating is more accurate than roll coating and more suited to the ultra-clean environment for display production. In addition, the fixed-lip design of Liberty dies make it possible to produce very thin and optically clear coatings while maintaining coat weight within close tolerances. In fact, a fixed lip is absolutely essential for the special process of draw coating, which prevents dies from coming into contact with the expensive machined rolls used in manufacturing prism film."
In the fifteen months since EDI acquired the Liberty® slot coating die business (shortly before last year's SID event), the company has expanded and strengthened the Liberty operation by drawing on its extensive engineering, manufacturing, and international marketing resources. As a result, Paradise said, the following advantages have emerged or become more broadly available to companies that apply precision coatings to FPD components:
Access to complete slot die coating lab. At its Chippewa Falls, WI, U.S.A. world headquarters, EDI has built a process laboratory that companies can rent for testing alternative fluid formulations, coating/substrate combinations, and other parameters without tying up their own equipment or using large quantities of raw materials. Practitioners of roll coating can explore the advantages of slot die coating before investing in a commercial-scale system. A company need not be a customer to use the lab, and confidentiality is assured by a nondisclosure agreement signed by EDI.
Modular coating system for trial runs in existing plants. Customers or prospects can roll EDI's WetWare(TM) slot die coating station into place in their existing coating lines, eliminating hours of setup.
Multi-layer dies that add new coating functions in one application. Using one of two options for producing multi-layer coatings (see below), manufacturers can add new functionality-for example, antireflective properties-without additional coating applications.
Global sourcing of coating dies and support service from EDI. As a company which has operated internationally for many years and sells half of its products outside the United States, EDI has vastly expanded access to Liberty die technology for companies around the world. The company operates full-service subsidiaries in Germany and China that provide remanufacturing or rework of existing dies, spare parts, and technical support. It has also licensed its die-rework technology to a company in Japan. The Chinese subsidiary started up around the time of EDI's acquisition of the Liberty die business last year.
Unlike slot coating dies that wipe coating fluids onto the substrate, EDI's Liberty system centers on coating heads with relatively large lip gaps (e.g., up to 3 mils) from which fluids can be drawn to coatings as thin as 1 micron. In commercial uses involving many fluids and substrates, Liberty slot dies maintained cross-web coat weight tolerances within 3 to 5% even at coating thicknesses of only 0.00008 in., or 2 microns.
Liberty Slot Die Coating System Is Easily Adapted for Wide Range of Uses
While the lip of the Liberty die is fixed, coating thickness and width can be varied by means of interchangeable shims (one of which is shown with the die halves in an accompanying photo).
For coatings of more than one layer, two options are available:
Dual- and Triple-Slot Dies. These dies include options for conversion to single-slot (i.e., single coating layer) dies. An accompanying photo of a dual-slot die, for example, shows a wedge-shaped center body that adds a second slot but can be removed, leaving the two die bodies that are standard for monolayer coating.
'Slide' or 'Cascade' Dies. For applications of up to ten layers or even more, these dies are made up of an array of die bodies set at an angle to the web (see photos). The array provides multiple slots. The coating fluid from the slot farthest from the web becomes the topmost layer; as this fluid slides down the face of the die toward the web, additional coating layers flow in beneath the top layer; the fluid from the slot closest to the web becomes the bottom layer.
EDI can produce single-slot Liberty dies for coating widths of up to 120 in. (3 m) and wet coat weights from less than 1 to 254 microns (10 mils). Liberty dies typically are shipped as part of a system including positioner (to maintain a precise orientation to the backing roll), vacuum box (to remove air trapped between the coating as it exits the die and the approaching substrate surface), and fluid delivery equipment (filters, pump, drive, and controller). As an option, EDI can incorporate in the positioner a die handling mechanism, called a "hinge," that enables operators to quickly split and clean the die, change shims if needed, and rebolt the die bodies. As with all other EDI dies, rework services are available to restore used dies to like-new condition.
Slot Die Coating Provides Important Advantages over Roll Coating
Slot die coating has emerged as a more efficient and controllable alternative to roll coating and other conventional methods of applying fluids to web substrates. One reason for the increased attractiveness of slot die coating is that the intense competition generated by industry consolidation and globalization has increased pressure to maximize economy, productivity, and quality assurance. Quality is especially critical in the electronic display industry. At the same time, there is a growing mandate for further reductions in emissions of volatile organic compounds (VOCs) from solvent-borne coating systems.
In roll coating, the amount of material deposited on the substrate is controlled indirectly by means of wiping blades or pre-set gaps between rollers; any excess coating material is scraped away and returned to the coating bath; and the bath itself is open to the workplace environment. Slot dies, on the other hand, are closed systems, and the amount of coating material is pre-metered by means of a precision pump. As a result, slot die coating provides these advantages: 1) more consistent coat weight and cross-web distribution; 2) higher line speeds; and 3) minimization of volatile emissions, coating contamination, raw material waste, and workplace messiness.
EXTRUSION DIES INDUSTRIES, LLC (EDI) is a leading international supplier of flat dies for sheet, film, extrusion coating, slot die coating, and pelletizing. The company designs and manufactures dies, feedblocks, deckling systems, vacuum boxes, and related equipment. Its subsidiaries include EDI GmbH in Reichshof-Wehnrath, Germany, and EDI China in Shanghai. In the U.S.A., Germany, and China, EDI operates facilities dedicated to reworking its own dies and those built by other suppliers, and it has licensed a fourth rework facility in Japan. Headquartered in Chippewa Falls, Wisconsin, U.S.A., EDI sells half of its dies outside the United States. Visit www.extrusiondies.com and www.reworkdies.com. E-mail: sales@extrusiondies.com.
Robert J. Martino
Martino Communications Inc.
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Hastings-on-Hudson, NY 10706 U.S.A.
Tel: 1-914-478-0754
Fax: 1-914-478-0959
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