What Is an Edge-Lit LED Backlight? Structure, Components and Applications

1.What Is an Edge-Lit LED Backlight?

The development of LED backlighting stems from advancements in liquid crystal modules. LED backlighting is primarily employed in flat-panel electronic display devices and liquid crystal displays, such as mobile phones, MP3 players, MP4 players, digital cameras, instrumentation, household appliances, gaming consoles, and watches.

As LCD (glass) panels themselves do not emit light, an illumination system positioned beneath the glass substrate is required—this constitutes the LED backlighting.

The fundamental requirement for LED backlighting is to provide sufficient brightness and uniform illumination for the glass screen, ensuring the liquid crystal glass display achieves high contrast and display quality during everyday use. The key to backlight design lies in achieving uniform light distribution across the light guide plate, which significantly determines the luminous performance of the LCD display.

2.Edge lit LED Backlight Structure (Primary Components)

1. Light source: Surface-mounted lamps, bracket lamps, bonded lamps
2. Light guide plate （LGP）
3. Plastic frame
4. Reflective film (sheet)
5. Diffusing film (sheet)
6. Light-blocking film

Introduction to Conventional Edge-Lit LED Backlight:

Structure: Light sources are positioned along the periphery of the light guide plate, emitting light parallel to the diffusion film (illuminated surface). Light propagates through reflection and refraction within the guide plate before being uniformly emitted from the diffusion surface. Standard side-lit backlighting employs either single-sided or dual-sided light entry.

Characteristics: Lightweight and slim structure, high brightness, excellent uniformity, low power consumption, diverse colours including red, green, blue, white, orange, tricolour, and multicolour.

Applications: Mobile phones, home appliances, banknote counters, and numerous other widespread uses.

Light colour, source parameters and specifications

Red (R): Operating voltage typically ranges between 1.8–2.3V, commonly operating at 1.9–2.2V under 15mA current.

Green (G): Operating voltage typically ranges between 2.9–3.4V, commonly operating at 2.9–3.2V under 15mA current.

Yellow-Green (YG): Operating voltage generally ranges from 1.85 to 2.3V, with common values between 1.9 and 2.2V at 15mA.

Amber (OR): Operating voltage generally ranges from 1.85 to 2.3V, with common values between 1.9 and 2.2V at 15mA.

Blue (B): Operating voltage typically ranges between 2.9–3.4V, commonly operating at 2.9–3.2V at 15mA.

White (W): Voltage typically ranges between 2.9–3.4V, commonly operating at 2.9–3.2V at 15mA.

1)LEDs are categorised into two main types:

1.SMD Surface Mount LEDs

Common types include 0603 and 3020 packages.

0603 package structure: 1.6 × 0.8 × 0.6 mm, 140-degree light emission angle, with correspondingly lower brightness.

3020 package structure: 3.0 × 2.0 × 1.3 mm, 100–140-degree light emission angle. Larger chip size enables higher brightness.

2. Mounted Lamps

Commonly used are 2×3×4 mounted lamps (also termed plug-in lamps), with a light-emitting area of 90–120 degrees. Constructed from epoxy resin, two metal mounting feet, and copper terminals, they represent a cost-effective choice.

2)Light guides plates types: moulded light guides and screen-printed light guide plate.

The materials for light guides plate are typically categorised into three types:

1. PMMA (also known as acrylic or PMMA sheet, used for screen-printed light guides)
2. Transparent polycarbonate (PC) material
3. Polystyrene (PS) material

Moulded light guide plates offer superior quality and consistent product uniformity, making them suitable for high-volume production. The underside of the light guide is manufactured with a patterned grid of small, raised dots distributed according to a specific design.

PMMA offers superior light transmission but is brittle with low heat resistance, typically withstanding temperatures up to approximately 80°C.

Transparent PC material boasts high transparency, excellent bendability, and superior heat resistance, making it suitable for complex structural products.

PS material also exhibits high light transmission but has slightly inferior temperature resistance, withstanding temperatures up to approximately 60°C.

3)Reflective Film

Reflective film is manufactured from PET through micro-foaming to create a reflective sheet. Its function is to redirect light escaping from the light guide plate back through the light-emitting surface, achieving a reflectance exceeding 90%.

4)Diffusion Film

The primary function of diffusion film is to homogenise light distribution within the light guide plate, mask screen-printed dots and shadows, enhance luminance (increase brightness), and alter the light path.

5)Light-Blocking Film

There are three Light-Blocking Film (Bright Silver Dragon, Matte Silver Dragon, Black/White Film)

Light-blocking film is affixed to the sides of the light guide plate and between the lamp and the VA layer.

1. Bright silver film exhibits a more lustrous sheen and greater thickness (0.08mm), offering superior light-blocking properties.

2. Matt silver film possesses a relatively subdued appearance and thinner gauge (0.05mm), allowing some light transmission.

3. Black-and-white film provides strong light-blocking capabilities and is non-conductive.

We are an experienced Edge-Lit LED Backlight manufacturer

We offer custom led backlight solutions based on specific mechanical, optical, and electrical requirements. From light source selection to light guide plate materials and optical film structures, our solutions are engineered to achieve high brightness, excellent uniformity, and stable performance.

For custom sizes, thickness constraints, colour specifications, or special applications, please contact us directly. We welcome technical discussions and project-based inquiries.