Edge-Lit vs Back-Lit LED Panels: Key Differences Explained

There are 2 type of led light panel: Edge-lit and Back-lit . What’s the difference between them?

LED Panel lights come in three main size categories: One is small-sized panel lights, such as downlights, where the light is emitted from side-mounted LEDs and transmitted through a light guide plate. They come in square or round shapes, with dimensions ranging from approximately 90mm to 225mm (diameter or side length), and power ratings of 3W, 6W, 9W, 12W, 15W, 18W, or 24W.

The second category is non-standard sizes, typically designed based on specific project requirements and unique dimensional parameters.
The third category is standard sizes, including 300x300mm, 300x600mm, 600x600mm, 300x1200mm, and 600x1200mm. Some regions may have slight variations in dimensions. For example, the dimensions of a 60×60 panel light are generally 595x595mm in China, 595x595mm in most of Europe, 600x600mm in most of South America, 603x603mm in North America, and 620x620mm in Germany and Brazil, among others.

Product Structure

1)LED Edge-lit Panel Light Structure and Light Emission Principle:

The structure of an Edge-lit LED panel light primarily includes components such as the frame, diffusion plate, light guide plate, light strip, reflective film, and backplate.

The light from the LED chips enters the interior of the light guide plate through the light-emitting surface. The light is reflected off the reflective points on the light guide plate and emitted downward, then emitted through the light-emitting surface of the luminaire. Light that does not hit the reflective points is reflected back by the reflective film, ensuring that most of the light from the LED chips is converted into usable illumination. The quality of the light guide plate is an important criterion for evaluating the overall quality of the Edge-lit panel light.

2) Structure and light emission principle of LED direct-lit panel lights:

The structure of direct-lit (direct-emitting) panel lights primarily includes a frame, diffusion plate, light strip (including aluminum substrate, LED chips, and lens), and back cover.

The light from the LED chips is scattered by the lens and reflected by the back cover, emitting from the light-emitting surface of the fixture.

Analysis of components of conventional led panel lights

1.Frame: Frame strength affects durability and the overall quality of the light fixture.
The frame is an important part of the panel light. A high-strength frame makes the panel light more durable. The materials used for the side frames of LED panel lights vary, resulting in different heat dissipation performance. The current materials for panel light frames primarily include aluminum alloy, steel, PC, A6063, aluminum-plastic composite, and steel. The most commonly used is the aluminum frame (for small panel lights, some use plastic housings), which is further divided into assembled and welded frames. Welded frames are more robust but more expensive than assembled frames. Generally, frames are categorized by style into flat frames and stepped frames, with price differences. Additionally, the weight of the frame (amount of material used) also affects the price.

2.LED chips
The type, brand, and quantity of LED chips affect the lighting effect, luminous flux, and price. Commonly used LED chips include SMD2835 and SMD4014, with brands such as SANAN, SUMSANG, and Lumileds (formerly Philips). LED chips from branded manufacturers are more expensive. Direct-lit panel lights, due to the light from the LEDs being scattered through optical lenses, generally require significantly fewer LEDs than Edge-lit panel lights.

3.Diffuser Plate: Different Materials Have Different Light Transmittance
The diffuser plate serves to evenly distribute light from the light guide plate and also helps blur pixelation. Common materials include PC, acrylic, PS, and PP. Prices range from high to low, with PS and PC being the most commonly used.

Acrylic has a light transmittance of 92%, PC is 88%, and PS is approximately 80%. Acrylic has higher light transmittance than PC and lower costs, but it has weaker aging resistance; PC is more expensive but has stronger aging resistance. Additionally, different manufacturers use different thicknesses for diffusion plates, with the most common being 0.8mm to 1.2mm thick, which are more expensive. Direct-emitting panel lights require higher strength in the diffusion plate compared to Edge-lit panel lights and are generally thicker.

4.Light guide plate (LGP)
The light guide plate is a component of Edge-lit panel lights. The material is a significant factor affecting light efficiency besides the LED chips. Its function is to refract light parallel to the direction of the light-transmitting plate into light perpendicular to the direction of the light-transmitting plate. The light refracted by the light guide plate is then reflected back by the reflective paper to the back of the panel light. During this process, it is also important to minimize light decay. Generally, the light efficiency of the light guide plate largely depends on the dot pattern design, followed by the choice of material (transmittance). Commonly used materials include PMMA (acrylic), MS, and PS, with prices decreasing in that order. However, PS and MS tend to yellow over time, with PS typically yellowing after about two years and MS after about three years. In regions with higher temperatures, light guide plates are more prone to yellowing. If a 5-year warranty or higher light efficiency is required, PMMA light guides are typically used. The dimensions of light guides used by various manufacturers generally range from 1.6 to 3.0 mm, with thicker options being more expensive.

5.Reflective sheet
Reflective sheets are used in panel lights to reflect scattered light back into the light guide system, enhancing light efficiency, improving brightness uniformity, and preventing backlight leakage.

6.Backplate
The most commonly used backplate is made of iron, with different thicknesses and weights resulting in varying strengths. Compared to Edge-lit panel lights, direct-lit panel lights have a different design, with thicker backplates. Additionally, the backplates of direct-lit panel lights undergo powder coating, which not only provides color but also enhances reflectivity.

7.Driver Power Supply
Prices vary based on brand, voltage, isolation (isolated is safer), flicker-free (affects whether the light appears flicker-free when photographed with a phone), functional requirements (e.g., dimming and color adjustment), and certification requirements.

8.Anti-Glare Film
Anti-glare requirements (UGR < 19 to prevent eye strain) necessitate installing an anti-glare film before the diffuser panel or using a diffuser panel with built-in UGR effects.

9.Installation accessories
Spring clips and mounting brackets are generally selected based on different customer needs.

Advantages and disadvantages of Edge-lit vs Back lit led panel lighting

Edge-lit panel lights offer advantages such as aesthetic simplicity, elegance and luxury, uniform and soft lighting, ultra-thin thickness, and ease of installation and transportation; however, they are difficult to achieve high luminous efficacy, currently around 120 lm/W, which requires significant costs. Additionally, panel lights using PS and MS light guides may yellow over time.

Back lit panel lights have the advantage of simpler technology and manufacturing processes, with semi-automated production lines reducing labor costs. They offer sufficient brightness and can achieve high luminous efficacy, currently reaching 135 lm/W, with minimal yellowing of the fixture and a price advantage over Edge-lit models; The drawbacks include a thicker and bulkier design, which appears less premium than Edge-lit panel lights, and increased packaging volume and shipping costs. Due to their hollow structure, they have higher transportation requirements compared to Edge-lit panel lights. Some direct-lit panel lights may have dark zones along the frame edges, particularly in models with slanted back covers. Currently, right-angled edge designs for direct-lit panel lights have emerged, eliminating dark zones and improving light uniformity.

As a professional manufacturer, we specialize in producing high-quality light guide plates (LGPs), diffuser plates, and reflective films. With years of experience in LED panel components, we provide reliable, efficient, and customizable solutions to meet various lighting requirements. Partner with us for superior materials and expert support in your next LED panel project.