Application Brief Marine Electronics Advantages of Surface Capacitive Technology for Marine Electronics Applications The ideal interface is a touchscreen, but it must be able to withstand all of the aforementioned conditions without negatively impacting the optical clarity of the display. This application brief explains the critical needs of the marine electronics industry and demonstrates how the 3M MicroTouch System SCT3250EX uses surface capacitive touch technology to achieve those goals. Introduction Electronic devices have been used in the marine environment for decades and largely consist of navigation or global positioning system (GPS) devices, fish finders, chart plotters, and radar and video displays. Typically these display-based devices range in size from 7-inches to 19-inches, and use buttons or joysticks to make selections or to move within a viewable area. In premium amateur boats and commercial marine vessels, these multiple devices are converging into one large display-based device that performs multiple tasks. The applications used in the marine environment can include 2D and 3D navigational charts, radar tracking to locate and track bird flocks to help pinpoint schools of fish, a satellite link to view high resolution aerial photographs, and in some instances live video feed for monitoring unmanned areas of the boat. Access to all of this information from one device creates a more enhanced and useful tool and an improved user experience. The convergence of these applications into a single device requires a common, flexible interface that provides intuitive access for the user. Mechanical and single function buttons will likely become obsolete for these devices as manufacturers increase the displayed content and become more versatile to enhance the user experience. In addition to the converging device design, the extreme conditions of the marine environment drives device requirements. These environmental conditions can include high ambient and direct sunlight, salt and fresh water spray, environmental condensation, wash down of gauges and electronic equipment to reduce salt water corrosion, elevated operating temperatures, sustained vibration from the engines and heavy jarring from rough waves. Critical Application Needs There are multiple high-level application needs for a touchscreen in the marine electronics market. They are: Optical Clarity Sealability Product Robustness Touch Accuracy Integrated Touchscreen Solution Worldwide support Optical Clarity Optical clarity is a broad category and contains several focus areas: Light transmission Anti-glare treatment Color Light transmission is the percentage of light that passes from a light source (like an LCD) through a touchscreen overlay and is registered by the user s eye. This transmission can be affected by optical coatings that may be placed on the touchscreen to provide touch functionality or to control device or environmental effects, such as LCD noise emission. Transmission can also be affected by the existence of an air gap between the front surface of the LCD and the touchscreen overlay. The air gap provides a medium in which the light scatters, reflecting back and forth between the LCD and back surface of the touchscreen. This reduces the amount of light traveling to the user s eye making the display appear dim or dark [FIGURE 1]. Optical bonding of the touchscreen to the LCD (eliminating the air gap) can minimize light reflection and results in brighter colors and enhanced color contrast. Anti-glare is a surface modification treatment, such as chemical etching, that is applied to the front surface of the touchscreen to reduce glare from sunlight or other external light sources. A touchscreen that lacks any anti-glare treatment will give the viewer the experience of a glossy-finished photograph. This type of finish is very shiny and
2 High Anti-Glare Figure 2. High and low anti-glare reflection comparison. Low Anti-Glare Figure 1. Affect of light transmission through an LCD-touch sensor air gap. finger prints are easily seen on the surface. An anti-glare treatment is the equivalent of a matte-finished photograph. The clarity of the picture is slightly reduced when compared to the glossy finished photograph. However, finger prints are not as easily seen and the shininess is gone, making it easier to see the displayed image under a wider range of light settings. There are varying degrees of anti-glare treatment. As the anti-glare characteristic increases the clarity and transmission will decrease [FIGURE 2]. The anti-glare treatment must be optimized to achieve satisfactory clarity and transmission. Color is a third aspect of optical clarity. There are three color coordinates that affect color and how it is perceived by the human eye. They are L*, a*, and b*. In 1976, the Commission Internationale d'eclairage (CIE) recommended a color scale where they defined color space in a cube format with L*, a*, and b* as dimensions in space within the cube. This cube format as defined by CIE is known as CIELAB [FIGURE 3]. The purpose of the scale is to provide an approximate uniform color scale. As shown, the L* axis runs from top to bottom and represents a color shift from white to black respectively. The a* and b* axes are orthogonal to each other. Movement along the axes in a particular direction defines the color correction needed to bring the sample back to true color. Color can be negatively affected by variables like ultra violet (UV) light, optical coatings, anti-glare treatments and any adhesives used to bond the system together. The result from the aforementioned possibilities can result in a color shift that can have a negative impact on the user s perception of color. Sealability Sealability is important since marine electronic devices are constantly exposed to salt and fresh water during use, not to mention inclement weather and the full wash down cleaning process. These devices are tested to an outdoor specification to ensure functionality even if they reside in an enclosed cockpit. Water entering the housing can lead to corrosion of the device electronics, shortening the life expectancy of the product. It can also short out the electronics that drive the display, Figure 3. CIELAB color scale again affecting product life expectancy. Water may also seep in and condensate on the screen, making the device unusable for a period of time until the condensation clears and the display can be clearly seen. All of these scenarios reinforce the importance of tightly sealing the touchscreen within the device to avoid these potential failure modes. Product Robustness A critical requirement for touch-enabled marine devices is product robustness, which can include a durable front surface, no wear or degradation of optical coatings that may be applied to the front surface, a standard shaking test, and wide operating temperature ranges. A vibration test is conducted by placing the marine electronic device on a shaking machine for a predetermined amount of time. This test mimics the boats sustained vibration from the engines and hard jarring from rough seas. Since marine electronic devices are on ships from the equator to the poles, these touch-enabled devices need to be reliable in a wide operating temperature range.
3 Touch Accuracy As more data-driven and detailed applications are being developed for marine electronic devices and with the convergence of multiple devices, the user interface icons are becoming more densely grouped. The more tightly packed the screen icons are, the more accuracy is required from the touchscreen to activate a specific icon among all the choices. Accuracy remains important within individual applications as well. Some navigation applications allow a chart to be developed when you accurately identify a start and stop location on the map. The ability to identify a specific location within a dense map enables the software to create the best passage from the current location to the desired location. Integrated Touchscreen System To help ensure the successful integration of touch-enabled devices that meet these critical application needs, device manufacturers expect the touchscreen manufacturer to supply a matched touch system that includes the touch sensor, touch electronic and often, touch drivers. Receiving a matched touch screen package helps ensure that the touch-enabled device will work optimally in the marine environment. It also provides the device manufacturer with one product source if there are issues with integration or product functionality. Worldwide Support Another important consideration for the device manufacturer is having reliable product support wherever the device is designed, manufactured and serviced. In most cases device manufacturers design the product in one location and manufacture it in another, either in their own facility or at a third-party contract manufacturing location. Either way the ability to interface technically in the local language at the point of design and the point of manufacture speeds the development process along and makes it easier to bring the product to market. The 3M Solution For marine electronic devices, the 3M MicroTouch System SCT3250EX (with either chipset or controller) is the best solution for the stated application needs [FIGURE 4]. The SCT3250 sensor is an all-glass, surface capacitive touch sensor with 3M-proprietary optical and anti-glare coatings. Light transmission of the SCT3250 sensor is 91.5% (±1.5%). This is slightly higher than plain borosilicate or soda lime glass which has a light transmission of approximately 90%. Borosilicate and soda lime glass are the most commonly used glass types for touch sensors. The lower transmittance of plain glass is due to light reflectance from the front and back surfaces of the glass. Light can come from the LCD, from an ambient source in the environment or can be direct sunlight. 3M's optical coatings enhance light coming from the LCD by scattering the ambient light from the front surface. [FIGURE 5] This surface scattering prohibits direct reflection back at the viewer, thus allowing light coming from the LCD to make its way to the viewer s eyes. The combination of Figure 4. The 3M MicroTouch System SCT3250EX and 3M MicroTouch Chipset EX these two coatings helps increase the brightness of the display image by enabling more light from the source to be seen by the users eye. Light transmittance can be increased by bonding the touchscreen directly to the LCD. As mentioned previously, the air gap between the LCD and the touch surface provides a medium through which light can be scattered, reflecting multiple times off the same surface and effectively decreasing the amount of light perceived by the eye. Closing the air gap with an optically clear adhesive enables light from the LCD to pass directly from the LCD source to the user s eye with minimal loss of light from reflectance and light scattering. 3M has extensive experience with optically bonding touchscreens to LCD's and is a leading manufacturer of optically-clear adhesives for various markets. Removing the air gap through optical bonding helps maintain its color Figure 5. Light transmission with optically-bonded, anti-glare option.
4 saturation, making it appear brighter and giving more depth to dark colors than unbonded displays, which in effect increases the contrast ratio of the display and makes it easier for the viewer to see the display image. It is critical to understand the material characteristics of the bonding material. Some bonding materials have negative interactions with chemical compounds that may be present on the touchscreen. The bonding material may cause an interaction that changes the electrical characteristics of the touchscreen making it non functional. The bonding material can also change the perceived color, so it is important to use materials that are color indexed properly. Color can be affected by optical coatings. 3M-patented coatings are designed to remain color neutral. This is achieved through matching the indices of refraction to ensure no single coating is reacting negatively to another coating. A negative interaction between coatings can lead to a hue or color shift as defined in CIELAB. Color can also be affected by UV light exposure, depending on the materials used in touchscreen construction. An example of a negatively impacted construction is a 5-wire resistive glass-and-polyethylene (PET) construction. With ongoing exposure to UV light, the PET can yellow, fade or crack. The amount of discoloration or change in the PET surface is in direct relation to the length of UV exposure and to the intensity of the exposure. The SCT3250 touch sensor is impervious to discoloration from UV exposure due to its all-glass construction. The all-glass construction not only provides a resistance to UV exposure but enables device manufacturers to seal the touchscreen within the device to a high "water ingress" standard of NEMA4 or IP66. These are two common industry standards which define the amount and velocity of water the device must be capable of withstanding. The glass thickness of SCT3250 sensor is 3.18mm (± 0.25mm) typical. The screen can be clamped to a bezel under force without damage and will continue to function under the pressure. Some technologies, like 5-wire resistive, struggle to achieve a water tight seal. 5-wire resistive sensors are made by separating two conductively-coated substrates with spacer dots. The force needed to create a water tight seal may inadvertently depress the spacer dots and put the two conductive surfaces in contact with each other thus creating a false touch input. Resistive touchscreen manufacturers suggest clamping the touchscreen outside the viewable area. This may make the integration of the marine electronic device more difficult and may require a wider border or bezel area. Figure 6 is a representation showing the difficulty in sealing resistive in a water tight device due to border area and sensor construction. The marine environment is one of extremes, so product robustness is very important. One major focus of this robustness is the durability of the touchscreen s front surface. Marine device manufacturers need to maintain the optical clarity of the display under environmental conditions like high UV exposure, as well as requiring scratch resistance for functional durability and optical clarity. The SCT3250 sensor is an all-glass solution that is unaffected by extended UV exposure, so it does not degrade or change color and thus maintaining its optical characteristics are maintained. 8.9mm border for typical 5-wire resistive Bezel 5.2mm border for 3M Surface Capacitive Bezel Sensor Figure 6. Border requirements for 5-wire Resistive versus 3M Surface Capacitive 3M s surface capacitive technology uses the proprietary 3M ClearTek Hard Coat and a separate scratch-resistant top coat. A common way to compare the scratch resistance of glass and other materials is to use the MoHs hardness scale. MoHs hardness refers to the ability of a material to resist scratches or abrasions. It was devised by Friederich Mohs in 1812 and ranks gemstones according to hardness. The softest gemstone has a rating of 1 and the hardest has a rating of 10. A diamond is representative of a 10 on the MoHs scale. The 3M ClearTek hard coat and scratch-resistant top coat provide functional scratch-resistance against common materials that have a MoHs rating of less than 7. Materials that fall into this category can create an aesthetic scratch, but not a functional scratch. Another aspect of robustness is the ability to operate in climates with very different temperature ranges. A marine electronics device can be found in the cockpit of a boat in the cold climate of the Arctic and in the warmer and more humid climate of the equator. The touchscreen system which includes electronics must be able to operate under these varying conditions. The SCT3250EX system is an all-glass solution that can operate in temperatures as high as 70 degrees C and as low as -40 degrees C. By comparison, a standard 5-wire glass-and-pet construction cannot generally operate in temperature ranges greater than 35 degrees C or less than -10 degrees C. Another concern for 5-wire resistive glass-and-pet touchscreens in use at higher temperatures is the different coefficients of expansion of the glass, PET and bezel materials of the marine device, which may lead to buckling of the PET top sheet when it is clamped tightly to the bezel. Because SCT3250 sensor is a single layer material construction it has a single coefficient of expansion and will not exhibit any of the issues of a 5-wire resistive glass-and-pet construction. As user interfaces become increasingly complex with more data available on the same display, the ability to accurately pick a specific icon becomes more difficult and more important. The reported touch coordinates of the SCT3250EX touchscreen system are within 1% of true position, based on the diagonal dimension of the touchscreen. This enables more icons to be displayed on the touchscreen without negatively impacting the ability of the user to accurately select the targeted icon. LCD Sensor LCD
5 Marine device manufacturers are interested in getting a complete touchscreen system from one manufacturer. This ensures that the electronics and the touchscreen work optimally together with reduced compatibility and integration issues. 3M Touch Systems sells component systems. Our electronics products can be purchased either as a separate controller that can be integrated into an overall design or can be provided as a chip set solution. The advantage of the chip set solution is it allows the device manufacturer to add the touchscreen circuitry and chip on to an existing board design. This effectively decreases the amount of space and can help shrink the overall design package of the electronic device. 3M touch products are supported by mechanical, electrical and firmware engineers who are able to maximize performance of the overall system. 3M understands the value of purchasing a touchscreen solution from one source that provides optimized functionality and maximum reliability. Marine device manufacturers are worldwide operations that are looking for the same support from their supply chain. Most manufacturers have multiple regional design centers with manufacturing occurring either in a third separate location or at a third-party integrator. The ability to support design centers and manufacturing locations with local, in-country personnel is important. The language barriers that can exist with companies that do not provide worldwide support are not an issue with 3M. The ability to communicate and technically support design centers and manufacturing plants shortens product development time. This enables the device manufacturer to develop a product and bring it to market faster, enabling them to respond to market and consumer needs more rapidly. Conclusions The 3M MicroTouch System SCT3250EX meets all of the critical application needs of the marine environment. The below table is a summary of the critical needs and benefits of the SCT3250EX system Application Needs Viewing Characteristics Optical Transmission Anti-Glare Color Sealing Capability Product Robustness Surface Durability Operating Temperature Touch Accuracy Matched System Worldwide Support SCT3250 Benefit 91.5% (± 1.5%) typical Patented anti-glare coating Neutral color. Unaffected by UV NEMA 4 or IP66 Hardness MoHs 7 or higher to induce a functional failure -40 to +70 degrees C Reported touch coordinates within 1% of true position based on diagonal screen size Available with electronics board or chip set system solution Offices in over 60 countries 3M Touch Systems Subsidiary of 3M Company 501 Griffin Brook Park Drive Methuen, MA 01844 U.S.A. 1-888-659-1080 www.3m.com/touch IMPORTANT NOTICE TO PURCHASER: Specifications are subject to change without notice. These 3M Touch Systems Products and software are warranted to meet their published specifications from the date of shipment and for the period stated in the specification. 3M Touch Systems makes no additional warranties, express or implied, including but not limited to any implied warranties of merchantability or fitness for a particular purpose. User is responsible for determining whether the 3M Touch Systems Products and software are fit for User s particular purpose and suitable for its method of production, including intellectual property liability for User s application. If the Product, software or software media is proven not to have met 3M Touch Systems warranty, then 3M Touch Systems sole obligation and User s and Purchaser s exclusive remedy, will be, at 3M Touch Systems option, to repair or replace that Product quantity or software mediator to refund its purchase price. 3M Touch Systems has no obligation under 3M Touch Systems warranty for any Product, software or software media that has been modified or damaged through misuse, accident, neglect, or subsequent manufacturing operations or assemblies by anyone other than 3M Touch Systems. 3M Touch Systems shall not be liable in any action against it in any way related to the Products or software for any loss or damages, whether non-specified direct, indirect, special, incidental or consequential (including downtime, loss of profits or goodwill) regardless of the legal theory asserted. (7/02) 3M and MicroTouch are trademarks of 3M Company. Printed in USA 3M 2009 All Rights Reserved. MARINE-ELECTRONICS-1109