Bright flashing advertising signs are a ubiquitous part of urban landscapes, captivating attention with their vibrant glow. These luminous displays, ranging from classic storefront signs to expansive digital billboards, rely on specific elements for their eye-catching effects.
The Role of Neon
The element most famously associated with bright signs is neon. Neon is a noble gas, meaning it is chemically stable and does not readily react with other elements. This inertness makes it suitable for use in sealed glass tubes for prolonged periods. When an electric current passes through neon gas, it emits a characteristic bright red-orange light.
The discovery of neon occurred in 1898 by British chemists Sir William Ramsay and Morris W. Travers. French engineer Georges Claude further developed this technology, showcasing the first modern neon lighting at the Paris Motor Show in 1910. Its striking red-orange hue quickly led to its widespread adoption for commercial signage in the 1920s.
How Light Is Created
The production of light in these gas-filled tubes relies on a process called gas discharge or ionization. When a high-voltage electric current is applied across the electrodes at each end of a sealed glass tube, it provides energy to the gas atoms inside. This energy causes electrons to be stripped from the gas atoms, creating positively charged ions and free electrons, forming a plasma.
As these free electrons move through the tube, they collide with other gas atoms, exciting their electrons to higher energy levels. These excited electrons are unstable and quickly fall back to their original, lower energy states. During this transition, they release the absorbed energy in the form of photons. The specific color of the emitted light is determined by the type of gas used, as each element has a unique electron configuration and energy level transitions.
A Spectrum of Colors
While neon gas produces a distinct red-orange glow, a full spectrum of colors in advertising signs is achieved by using other noble gases or through additional techniques. For instance, argon gas, often combined with mercury vapor, typically emits a blue or lavender light. Krypton can produce a whitish-blue light, and xenon often results in a blue or deep lavender glow.
Beyond using different gases, manufacturers can create a wider range of hues by coating the inside of the glass tubes with phosphors. These phosphor coatings absorb the ultraviolet light produced by the ionized gas and re-emit it as a different, visible color. For example, green neon signs often use argon gas with a specific phosphor coating that reflects green. Colored glass tubing can also play a role in modifying the final appearance of the light.
Beyond Gas-Filled Tubes
The landscape of bright advertising signs has expanded beyond traditional gas-filled tubes. Light Emitting Diodes (LEDs) have emerged as a dominant technology in contemporary signage. Unlike gas-discharge lamps, LEDs produce light through electroluminescence, where semiconductor materials emit light when an electric current passes through them.
LED signs offer several advantages over their gas-filled predecessors, including higher energy efficiency, often consuming 70-80% less power. They also have a longer lifespan, frequently lasting 50,000 hours or more, which reduces maintenance and replacement costs. LEDs are more durable due to their solid-state construction, making them less susceptible to breakage than fragile glass tubes. Furthermore, LED technology provides greater versatility in design, enabling dynamic digital billboards that can display complex images, text, and real-time content.