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Vacuum Fluorescent Displays (VFDs) have been widely accepted for automotive applications in the U.S. and other countries because of their excellent performance capabilities such as high luminance, high reliability and low voltage operation. Recently, more compact and lightweight VFD packaging has been requested for use in limited-space applications and to achieve smaller overall system size, while concurrently pursuing a higher graphic-to-glass area ratio and maintaining VFD's excellent viewing angle capability. An Ultra Light Vacuum Fluorescent Display (UL VFD) has been developed to meet these challenges which has 14% thinner package thickness and 30% larger available graphic area compared to conventionally produced VFD. This paper discusses the development of UL VFD and its subsequent evaluation and testing.

Several types of Vacuum Fluorescent Displays (VFDs) are currently used for Head-Up Display (HUD) systems. To meet the requirements for HUDs which project the displayed information directly on the front windshield of a car, VFDs must be capable of displaying images at a luminance ten times greater than VFDs which are installed within the instrument panel. Since VFD technology was first selected for an automotive HUD system in 1988, the luminance improvement of the display has been the driving force in improving the system performance. Today's VFDs can generate extremely high luminance of 35,000cd/m2. This was developed through new innovations in materials and construction techniques. This paper discusses the development of an ultra-high luminance VFD for HUD system and its reliability.

The luminous efficiency of yellowish green and blue phosphor has been greatly improved. A luminance of 400 cd/m2 can be obtained at 12V with the yellowish green phosphor, whose luminance efficiency increased to 130%. This improvement suggests that the yellowish green phosphor can be used in the 12V driven VFD for the automotive application as well as greenish yellow and yellowish orange (1)*, (2)*. With respect to the blue phosphor, the luminance efficiency has been increased up to 160%, thus reducing the input power down to about 63%. By the continuing improvement, the blue phosphor will also be available in the 12V driven VFD.

The evaluation was made on phosphors of seven different colors in current use under high brightness ambient conditions. As the result, the use of an appropriate filter (e.g. Neutral Density Filter of 3.4% transmittance) allows the 3-digit numbers in the display of about 400cd/m2 to be read correctly under an ambient illuminance of 50,000 lx, regardless of colors used. On the contrary, when a filter of high transmittance, such as Neutral Density Filter of 10%, is used, the required display luminance in the same ambient differs depending on phosphors; 300cd/m2 for reddish orange to 1,600cd/m2 for greenish yellow.

The luminous efficacy of Vacuum Fluorescent Display (VFD) phosphors has improved steadily. Today, in addition to the standard blue-green phosphor, two additional colors can be driven directly by a twelve volt battery. Studies are continuing on other phosphors and are also reviewed in this paper.

Vacuum Fluorescent Displays have been manufactured for automotive applications for over six years. During this period, various technological advances, such as increased brightness, multicolors, and decreased power consumption have lead to the rapid expansion of the Vacuum Fluorescent Display (VFD) market. The following paper will discuss high brightness displays for automotive applications, focusing on large scale displays. These large scale displays are now becoming practical for mass production. We will discuss various design problems that are encountered and how to solve them; plus what performance criteria is targeted for future improvement.