Industrial & Specialty Printing - July/August 2012 - 31

Elastic printing plate

Printing plate

Printing substrate

Impression cylinder

Anilox roller

Figure 2 Original Sharp microwave membrane switch

Cells of the anilox roller

Figure 3 Typical ﬂexographic process

Ink supply with chambered doctor blades

Figure 4 Halo eﬀect with ﬂexography printing

PE which would have been hard to imagine in the 1900s. In modern history, a fully functional and reliable printed electronics device was introduced to the consumer in the early 1980s. This device was the membrane keypad or membrane switch. Consumers were rst introduced to this convenient, low-cost electronic device as the touch panel or user interface in a microwave oven (Figure 2). Clearly, we have come a long way since the introduction of membrane switch in the early 1980s. Today, you nd printed electronics devices in almost all industry sectors. If you have been to a printed electronics show recently, you have seen what the future holds for printed electronics. Experts predict that soon printed electronics will enable us to have edible, foldable, rollable, wearable, disposable, and biodegradable electronic devices. However, rst there are many obstacles one must overcome to make these predictions come to reality. Out of many, two that stand out the most are high-performance, functional materials and low-cost manufacturing techniques. MARKET OPPORTUNITY Consumer demand for greater functionality, higher performance, higher reliability, and lower cost electronic devices is driving the electronics industry to nd alternative manufacturing methods to meet these demands. PE is probably the most promising technology that has the potential to meet all of these demands. IDTechEx predicts the market for printed and potentially printed electronics to reach $9.4 billion in 2012. Furthermore, by

2021, the market is predicted to reach over $44 billion, according to their predictions. This quadruple growth over ten years is predicted to come from consumer electronics, military, power generation, healthcare, and logistics. Among all industry sectors, consumer electronics is the driver behind most all new technology developments. However, consumer electronics are also most sensitive to cost. Experts agree that the only way to meet this demand is through a low-cost manufacturing process. Printing technologies such as exography, gravure, and inkjet are taking advantage of this opportunity by using a broad range of materials to meet consumer demands. Depending on the application, each printing technology has its unique advantages. For example, exography and gravure printing are highly suitable for roll-to-roll printing on plastic substrates. Both of these printing processes are very fast and well suited for producing variety of products starting with RFID to low-end exible, disposable displays. On the other hand, inkjet printing is highly suitable for applications where contact printing is not an option. Inkjet printing has the advantage of being a non-contact digital printing method, which also can be used in roll-to-roll or batch processes for all types of substrates. PRINTING TECHNOLOGIES Printing technology can be divided into two major categories, contact printing and non-contact printing. The common types of contact printing used in printed electronics are screen, offset, exography, and gravure. In contact printing, the pattern is transferred to the substrate via direct contact

with the printing mask or printing plate. Contact printing is analog in nature and can be cost prohibitive if running a small, batch process. In non-contact printing, the image or pattern is transferred to the substrate through a non-contact process. Because this process requires no printing mask or plate, it is cost effective for both batch and continuous process. One of the most commonly used digital printing techniques is piezo actuated inkjet printing. Each technique has its own advantages and disadvantages in regards to manufacturing electronics devices. Even though most all printing methods have been used for printed electronics manufacturing, exography, gravure, and inkjet have the most advantage in regards to resolution and cycle time. Hence, these three technologies warrant further investigation. FLEXOGRAPHY Flexographic printing is a more than 100-year-old process, which is basically a rubber-stamp technique. In this printing technique, a exible stamp, known as cliche, is wrapped around a cylinder to provide continuous printing process on plastic or metal-foil substrate. Figure 3 shows a typical exographic process. The key components of a exography printing process are ink supply chamber, doctor blade, anilox roller, plate cylinder with printing plate and impression cylinder. The anilox roll contains tiny cells or wells on its surface which gets lled in a controlled manner by the chamber doctor blade. These tiny amounts of ink are transferred to the printing plate as the two rollers pass each other. The amount of ink transferred
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Industrial & Specialty Printing - July/August 2012

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