Invented by Chang Ho Shin, Samsung Electronics Co Ltd
The Samsung Electronics Co Ltd invention works as followsA LED backlight unit comprises a substrate with a plurality light emitting diodes on it, and a plate of light guide adjacent to the source. The light source and light guide plate are fixed in a chassis. Fixing means engagently fit one side of the guide plate in the light source plate, and chassis. The substrate of the source of light is fixed on the surface of the chassis. Light guide plate can be assembled without thermosetting adhesive.
Background for LED backlight unit with light guide plate and fixing means
The invention is a backlight using a LED and, more specifically, it is a LED backlight in which the light guide plate can be assembled without the use of a thermosetting glue that would affect the brightness of the LED. This ensures a higher radiation efficiency from heat generated by the LED and, therefore, maintains high brightness and increases productivity.
The development of the electronic device industry has also led to the development of various small display units with a lower energy consumption rate. These devices are used in image devices, computer terminals, and mobile telecommunications terminals. In line with the trend, a liquid crystal display (LCD), which is a display for mobile telecommunications terminals and monitors, has emerged.
In general the LCD does not generate light on its own, so a backlighting unit is required, including a source of light for illumination and a guide plate to direct light onto the LCD panel’s rear.
The backlight unit produces a white glow so that the LCD screen can produce an image with almost lifelike color.
FIG. “FIG. The light emitting diode (LED) used in the conventional backlight unit 100 generates light by virtue of luminescence (electroluminescence) arising when voltage is applied to a semiconductor.
The LED has a smaller size and a longer useful life than conventional light sources. The LED is a high-efficiency light source that has a low driving voltage. This is due to the direct conversion of electrical power into optical energy.
As shown in FIG. A light source 120, light guide plate 130 and diffuser sheets (140 and 150) are located inside the bottom chassis 110. They are fixed to this chassis by a middle chassis and mold frame 162.
The light source 120 consists of a substrate (MCPCB), which has superior heat-radiation properties, and a number of light emitting devices (LEDs) 124. The LEDs 124 in this case are arranged on the substrate 122 in rows and are electrically connected to a power supply voltage external (not shown).
The light guide plate is flat and made from a transparent acrylic. The light guide plate is linear on one side, which is adjacent to the source of light 120. The light guide 130 diffuses the LED light from its entire top surface. “A reflective film (not shown) is fixedly placed on the underside of the plate to direct light only towards the top surface.
The diffuser sheets are flat sheets of the same type as the light-guide plate 130 and are disposed on it. The diffuser sheets serve to diffuse uniformly the light propagated by the light guide plate.
Further the prism sheets are disposed on diffuser sheets to induce light into an image forming area of an LCD panel located above.
As described above, a substrate 122 with a number of LEDs 124 is attached to a lower chassis via a thermosetting glue 112, as shown in FIGS. “As described above, the substrate 122 with a plurality of LEDs 124 disposed thereon is fastened onto a lower chassis 110 via a thermosetting adhesive 112, as shown in FIGS.
The thermosetting adhesive 112 fixes the light source 112 onto the lower chassis 110, which is fixedly positioned in relation to the light guide plate.
Also to prevent that the guide light plate is pushed towards the LEDs of the light source, a 114 attachment has been placed on both sides of an inner perimeter of the lower chassis.
Consequently, the light from the LEDs of the light source is directed outside via the light guide plate 120 and then through the diffuser sheets and prism sheets.
The LEDs 124 in the conventional rearlight unit 100 emit heat when they are emitted, which greatly reduces the brightness of the LEDs. In this way, the LEDs, if they are unable to radiate heat smoothly, will gradually reduce their brightness.
To ensure that such heat radiating effects are achieved, the LEDs have been arranged on the substrate to effectively radiate heat outward. The thermosetting adhesive 12, which is used to attach the substrate 122 to the lower chassis, 110, significantly reduces heat radiation.
What’s more, a substrate that is warped cannot be separated adequately from the light-guide plate 130 on the warped part, and therefore, it will not achieve the desired high brightness.
In addition, when assembling the substrate 122, the thermosetting glue 112 should also be applied to the rear surface of the substrate.” If the adhesive is applied incorrectly, it can smear on the LEDs, which will block the light.
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