As night falls, lightboxes displaying scrolling promotional information on shopping mall exteriors, advertising lightboxes guiding directions in subway stations, and flashing sign lightboxes at convenience store entrances... These ubiquitous light-emitting devices have long become an indispensable part of urban night scenes. Why can they continuously and evenly emit light to clearly present images? Behind this lies an exquisite "collaboration" between light sources and light-transmitting materials.

If a lightbox is compared to a light-emitting body, then the light source is its "heart", responsible for providing a continuous supply of light energy. With the development of technology, the light sources used in lightboxes have undergone multiple iterations, and currently, the mainstream ones are fluorescent lamps and LED lamps.

Early lightboxes mostly used fluorescent lamps, which generate ultraviolet rays through the discharge of mercury vapor in the tube, exciting the phosphor on the tube wall to emit light. This type of light source has low cost and moderate brightness, but it has obvious shortcomings: high energy consumption, short service life (usually 5000-8000 hours), and uneven light distribution, which easily forms "light spots" on the surface of the lightbox. In addition, fluorescent lamps contain mercury, which can pollute the environment if not properly disposed of after being discarded. Nowadays, they have gradually been replaced by more environmentally friendly LED lamps.

LED (Light-Emitting Diode) is currently the "main force" in lightboxes. It emits light through the electrification of a semiconductor chip and has three major advantages: energy saving, long life, and environmental protection. Its energy consumption is only about 30% of that of fluorescent lamps, its service life can reach 50,000-100,000 hours, and it does not contain harmful substances such as mercury. More importantly, LED lamps are small in size and can be flexibly arranged into light strips or lamp bead matrices, which can be adjusted according to the size and shape of the lightbox to make the light distribution more uniform. For example, large outdoor lightboxes often use high-density LED light strips to ensure that every corner of the picture is illuminated; while small sign lightboxes can meet the demand with just a few LED lamp beads.

With the "energy" provided by the light source, a layer of light-transmitting material, like "skin", is needed to guide the light, allowing the image to be presented clearly and softly. The core functions of light-transmitting materials are diffusing light (to avoid glare or light spots caused by direct light from the source) and carrying images (printing or pasting advertising content). The common ones are acrylic panels, lightbox fabrics, and diffuser panels.

Acrylic panels (organic glass) are commonly used materials for indoor lightboxes. They have a light transmittance of over 90%, are hard, wear-resistant, and have a smooth surface, which can make light scatter evenly and make the picture colors bright. However, acrylic panels have high cost and weak impact resistance, so they are not suitable for harsh outdoor environments and are therefore more used in indoor scenes such as shopping malls and hotels.

Lightbox fabric is the "first choice" for outdoor lightboxes. It is woven from PVC materials and coated with a special coating on the surface. It not only has good light transmittance (about 70%-80%) but also has strong weather resistance - it can resist extreme weather such as ultraviolet rays, wind and rain, and high temperatures. Even in environments of minus 30°C or plus 60°C, it is not easy to crack or fade. In addition, lightbox fabric is soft and can be made into large curved lightboxes to adapt to various irregular building exteriors.

Diffuser panels are the "hidden heroes". They are usually installed between the light source and the acrylic panel or lightbox fabric. The surface has tiny concave-convex textures, which can convert the direct light from the light source into soft diffused light, completely eliminating light spots. In some lightboxes with high requirements for light uniformity (such as X-ray viewing lightboxes in hospitals), diffuser panels are essential components.

The "collaboration" between the light source and the light-transmitting material is key to balancing brightness and uniformity. For example, if LED lamp beads are directly facing the lightbox fabric, obvious bright spots will be formed; but if a diffuser panel is added between them, the light can evenly cover the entire picture after refraction and scattering.

At the same time, different scenarios have different requirements for "collaboration": outdoor lightboxes need high-brightness LED lamps combined with weather-resistant lightbox fabrics to resist direct sunlight; while museum cultural relic display lightboxes require low-ultraviolet LED lamps paired with anti-glare acrylic panels to ensure the display effect while avoiding damage to cultural relics.

From billboards on streets and alleys to precision equipment in laboratories, the secret of lightbox illumination is essentially human control and utilization of light. When the energy of the light source is perfectly combined with the guidance of light-transmitting materials, these practical and aesthetically pleasing light-emitting devices are created, silently lighting up our lives.