The reason why the acrylic panel (PC) of a top-mounted luminous board embedded in the ceiling must be more than 3mm thick is primarily related to durability, safety, light diffusion, and structural integrity. Here's a detailed explanation:

1. Impact Resistance

   - 3mm thickness provides enough structural strength to withstand potential impacts or accidental pressure. Since the panel is likely to be exposed to various environmental conditions or physical interactions, having a sufficient thickness helps prevent cracking or breaking under light impact.

2. Light Diffusion and Quality

   - Acrylic (PC) is often used because of its excellent light diffusion properties. A 3mm panel thickness offers a balance between light distribution and structural support. Thinner panels may not diffuse light as effectively, leading to uneven lighting or hot spots, while thicker panels might reduce the overall brightness and lead to a bulkier, less aesthetic design.

3. Heat Resistance

   - A 3mm thick panel helps in managing heat dissipation from the lighting system. The LED lights or light source inside the luminous board can generate heat, and a thicker acrylic panel can resist warping or distortion due to heat exposure, ensuring the system operates safely over time.

4. UV Resistance

   - Acrylic (PC) panels, when UV-treated, provide better resistance to yellowing and degradation. A 3mm panel provides an ideal balance between UV protection and maintaining long-term aesthetic quality without degrading under sunlight exposure.

5. Structural Integrity

   - A 3mm thick acrylic panel ensures that the luminous board maintains its shape and integrity over time, especially when it is embedded into the ceiling. Thicker panels also provide extra protection against sagging or deformation due to gravity, temperature changes, or humidity.

6. Safety Considerations

   - A thicker acrylic panel is generally safer, as it reduces the likelihood of cracking or breaking if accidentally struck. In environments where safety is a concern (such as public areas or buildings with high foot traffic), a 3mm thickness provides an additional level of protection to ensure that the panel remains intact and functional.

The 3mm thickness for the acrylic (PC) panel in a ceiling-mounted luminous board strikes a balance between durability, light diffusion, heat resistance, and safety. It ensures optimal performance while maintaining the structural integrity and safety of the system, making it an ideal choice for both functional and aesthetic requirements.