Frequently Asked Questions

Who invented the fluorescent tube? Why does it resemble the glow tube? What is a fluorescent display screen? Why is it called a vacuum fluorescent display (VFD)? Will its lifespan be shorter than that of a glow tube? Can its color change? I had these questions when I first saw a fluorescent tube.

VFD technology was developed in the 1950s by American engineers and physicists. The first vacuum fluorescent display (VFD) was based on traditional gas discharge tubes, but it operated in a vacuum environment. It typically used a vacuum tube containing electrodes and a fluorescent coating. Electrons flow from the cathode to the anode, exciting the fluorescent material and generating visible light, which displays digital or character information.

Among the three major display technologies (VFD, LED, LCD), VFD was the first to be developed. Although LED and LCD have the advantages of lower cost and lower power consumption, they do not emit light by themselves and require an external light source to illuminate them. VFD, on the other hand, emits light on its own, with high resolution, high brightness, and ultra-wide viewing angles. It is still widely used in electronic devices and in special climate environments to this day.

Both glow tubes and vacuum fluorescent tubes were extensively used in industrial, aviation, and consumer electronic products during the Cold War era. This is why they are frequently mentioned in products like radios, audio equipment, and car dashboards. The only visual difference between glow tubes and vacuum fluorescent tubes is that the vacuum tube requires a black cover, known as a getter, whereas the fluorescent tube typically emits light through the interaction of mercury gas and electrical current. During the manufacturing process, the mercury gas may contain impurities or oxides, which can affect the performance of the fluorescent tube, causing a decrease in light efficiency or a shorter lifespan. The getter can absorb these impurities, maintaining the purity of the mercury gas and thus improving the light efficiency and stability of the tube. During the sealing process of the fluorescent tube, moisture may enter the tube, which can react with the mercury vapor to form mercury hydroxide or other compounds. This not only reduces the tube’s efficiency but may also corrode the electrodes. The getter absorbs this moisture, preventing it from entering the tube and ensuring that the mercury gas remains in an optimal working condition. Furthermore, the electrodes and other metal parts inside the tube are prone to oxidation at high temperatures. The getter absorbs oxygen in the tube, reducing the risk of oxidation of the metal electrodes, thus extending the life of the electrodes and maintaining the stable operation of the fluorescent tube.

The earliest fluorescent display tubes were divided into two categories: side-lit and top-lit. As fluorescent display technology matured, the demand for fluorescent tubes increased due to various applications. The four major production regions were the United States, China, the former Soviet Union, and Japan. Because early fluorescent tubes could only display numbers and at most simple symbols, they were unable to meet the growing application needs as technology progressed. This led to the development of the vacuum fluorescent display screen. The reason fluorescent tubes can be made into display screens is that they are capable of controlling different regions of fluorescent powder in a vacuum, which emits light to display multiple dynamic characters or graphics, offering greater control and flexibility in display capabilities.

The manufacturing process for both fluorescent tubes and fluorescent display screens is complex, requiring highly precise production techniques. It involves vacuum sealing, electronic tube technology, and the coating of fluorescent powders. These processes demand high-precision equipment and technology, making the production process relatively expensive. Additionally, the manufacturing of fluorescent display screens requires strict quality control to ensure the stability of the display effect. Compared to modern LCD and OLED displays, the production cost of fluorescent tubes is higher, and currently, there are fewer manufacturers producing them. As a result, there are fewer people creating these screens today.

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